PRACTICAL

ELECTRONICS
JANUARY 1975 25p

AKE
THIS
LIGHT *
PIPE
 NEW EDU-KIT MAJOR
COMPLETELY SOLDERLESS ELECTRONIC CONSTRUCTION KIT
BUILD THESE PROJECTS WITHOUT SOLDERING IRON OR SOLDER
4 Transistor Earpiece Radio
Signal Tracer
7speakerTransistor Loud-
Radio MW/LW,
2liveTransistor
Radio
Regenera-
Signal Injector
Transistor Tester NPN
5WaveTransistor
Radio
Short 3tiveTransistor
Radio
Regenera-
-PNP Electronic Metronome Audible
4 Transistor Push Pull Electronic Noise Genera-
for
Tester
Sensitive Pre -Amplifier
Continuity

TOTAL BUILDING COSTS

5Amplifier
Transistor Push Pull Batterylesa Crystal Radio.
One Transistor Radio

27.
Amplifier
P.P. & INS. 44p Components include:
(Overseas P.P. 24 Resistors 5 51 Capacitors 10 Transistors 3/' Loudspeaker Earpiece Mica Baseboard
3 15 -way Connectors 2 Volume Controls 2 Slider Switches 1 Tuning Condenser 3 Knobs
VAT 371, EI.85p) Ready Wound MW/LW/SW' Coils Ferrite Rod 61 yards of wire I yard of sleeving, etc.
Parts price list and plans 50p (free with parts)

NEW t. NEW ROAMER

TEN
ROAMER 7' EVERYDAY WITH VHF
NINE SERIES INCLUDING
AIRCRAFT
WITH V.H.F. Build this exciting New series of designs 10 TRANSISTORS.
Transistors and diodes. MW/LW. 9 TUNABLE
INCLUDING EVS 2
WAVEBANDS,
Powered by 41 volt Battery. Ferrite rod MW1, MW2, LW,
AIRCRAFT aerial, tuning condenser, volume control, and now with
Nine Tran- 3" loudspeaker. Attractive case with red speaker grille. SW1. SW2, SW3,
sistors, Size 9in x 51 in x in approx. Parte price list and TRAWLER BAND,
Tunable wave- plans 15p (FREE with parts). VHF AND LOCAL
bands as STATIONS. ALSO AIRCRAFT BAND
TOTAL P.P. & INS. Latest 4" 2 watt Ferrite Magnet Loudspeaker.
Roamer Ten. Built BUILDING 22.95 (VEREAS Built-in ferrite rod aerial for MW /LW.
in ferrite rod aerial for MW/LW. Chrome plated 7 section telescopic aerial, can be
Retractable chrome plated telescopic aerial for V HE COSTS
VAT 23p) PO &
P. PS. El '25)30p
and SW. Push Pull output using 600 mW transistors. angled and rotated for peak short wave and VHF
9 Transistors and 3 diodes, tuning condenser with EV6Case and looks as above. listening. Posh -pull output using 600inW transistors.
VHF section, separate coil for aircraft, moving coil 6 Transistors and 3 diodes. Powered by 9 Car Aerial and tape record sockets. 10 transistors
I oudspeaker, , volume ON/OFF and wavechange controls. volt Battery. Ferrite rod aerial, 3' loudspeaker, etc., plus 3 diodes. Ganged tuning condenser with VHF
Attractive all white ease with red grille and carrying MW/LW coverage. Push Pull Output. Parts price section. Separate coil for Aircraft Band. Volume/on/
strap. Size 91in x Tin x 2:in approx. Parts price list list and plans 15p WEER with Parts.) off, wave change and tone controls. Attractive case
and plans 30p it') parts). TOTAL 30p in black with silver blocking. Size 9in x Tin x 4m.
TOTAL P.P. & INS. 44p
BUILDING 23.60 (OVERSEA Easy to follow instructions and diagrams. l'arts price
list and plans 302 (FREE with parts).
COSTS P. & P. EIS25)p
BUILDING £695 (OVERSEAS VAT 29p)
28.5 P.P. & INS. 521,
I
TOTAL
+ v .,.)p P. & P. El 85)
COSTS
Ev7 Case and looks as above.
7 transistors and 3 diodes. Six wavebands.
BUILDING
COSTS
(OVERSEAS
P. & P. E1.85)
MW/LW, Trawler Band, SW1, SW2, SW3, powered -% \-. kr ,;,,.
be 9 volt Battery Push Pull Output. Telescopic Aerial
POCKET
i

for Short Waves. 3' Loudspeaker. Parts price list

and easy build plans 20p. 1)); cc with parts.
FIVE TOTAL P.P. & INS. 311,
NOW WITH 3'
LOUDSPEAKER
BUILDING
COSTS 24.0 V.VP 32id
(OVERSEAS
P. & P. El .85p)
EDU-
3 Tunable wavebands. KIT
MW/LW and Trawler '
Band. 7
transistors
stages,
and
5 ROAMER EIGHT Mk. I Build Radios
Amplifiers, etc.,
diodes, supersensitive ferrite Total Building Costs NOW WITH from easy stage,
rod aerial, attractive diagrams.
Black and Gold Case. Size
5fin X 11 in X 31in approx.
Plans and parts price list 15p (
22'50
V AT top)
VARIABLE
TONE CONTROL
(FREE with parts) P.P. & Ins. 26p 7 TUNABLE WAVEBANDS:
(Overseas P. P. 1E1.25) MW1, MW2, LW, SW1,
SW2, SW3 AND TRAWLER BAND. Built-in ferrite rod
aerial for MW and LW. Chrome plated telescopic
TRANSONA aerial can be angled and rotated for peak short-
s, ave listening. Push-pull output using 600mW
Five units
including master unit
transistors. Car aerial and tape record sockets. to construct.
FIVE NOW WITH Selectivity switch. 8 transistors plus 3 diodes. Latest 4' Components include: Tuning Condenser: Volume
3" LOUDSPEAKER watt Ferrite Magnet loudspeaker. Air spaced ganged Controls: S Slider Switches: Fine tone 3' moving coil
tuning condenser. Volume/on/off, tuning, wave change Speaker: Terminal Strip: Ferrite Rod Aerial: Battery
Wavebands, transistors and tone controls. Attractive case in rich chestnut shade
and speaker as Pocket with gold blocking. Size 9in x Tin x 4in approx. Easy Clips: 4 Tag Boards: 10 Transistors: 4 Diodes:
Total Building Costs Five. Larger Case with to follow instructions and diagrams. Parts price list Resistors : Capacitors : Three /in Knobs. Units once
e P.P. & Ins. Red Speaker
Grille and Plans 25p (FREE with parts). constructed are detachable from Master Unit, enabling
26p and TuningDial. them to be stored for future use. Heal for Schools,
Plans and parts price TOTAL P.P. & INS. 47p Educational Authorities and all those interested in
(-1- VAT 21p, list 15p (FREE with BUILDING 26.98 (OVERSEAS radio construction. Parts price list and plans 25p
(Overseas P. & P. E1'25) parts). COSTS P. & P. E1.85) (FREE with parts,.
.56p)
TOTAL P.P. & INS
BUILDING £5.50 (OVEREAS
COSTS P. & P. 1E1.. 85)33p
TRANS EIGHT 8 TRANSISTORS AND 3 DIODES + s%VAT 44r)
8 TUNABLE WAVEBANDS, MW, LW. SW!, SW2, SW3 AND TRAWLER
BAND. Sensitive ferrite rod aerial for MW. and LW. Telescopic aerial for
short waves. Sin speaker. 8 improved type transistors plus 3
diodes. Attractive case in black with red grille, dial and black
knobs with polished metal inserts.
Size 9in X 5fin X Olin approx. Push-
pull output. Battery economiser TOTAL BUILDING COSTS 'Callers side entrance "Lavells" shop
switch for extended battery life. 'Open 10-1. 2.30-4.30. Mon. -Fri. 9-12 Sat.
Ample power to drive a larger speaker Parts.
price list and plans 25p (FREE with parts).
14.48
P.P. & INS. 33p
(OVERSEAS
P. & P. El 25)
pm momommumniemEmiim
, AT 3Opi
To RADIO EXCHANGE CO., 61a HIGH STREET, BEDFORD MK40 ISA
Tel. 0234 52367 Reg. No. 788372
CASE AND LOOKS AS TRANS EIGHT
ROAMER SIX 8 TUNABLE WAVEBANDS: MW, LW, SW1, SW2.
TRAWLER BAND PLUS AN EXTRA MW BAND enclose £ for
FOR EASIER TUNING OF LUXEMBOURG. ETC. Sensitive ferrite roil aerial and tele-
I

111
scopic aerial for short waves. 3in speaker. 8 stages -
6 transistors and 2 diodes, etc. Attractive black TOTAL BUILDING COSTS
Name
case with red grille, dial and black knobs with P.P. & IN. 31p
polished metal inserts. Size 9in X 5f in x Olin approx.
Plans and parts price list 25p (FREE with parts). 3.98
( + % V A T ail))
(OVERSEAS
P. & P. 81.85) 1.
Address

IINMEMONIMMEIMIaiMM/MiNUOMMINEPE) 1.1
PRACTICAL
ELECTRONICS
VOLUME 11 No. 1 JANUARY 1975

CONSTRUCTIONAL PROJECTS
LIGHT PIPE by R. Gwynn
A novel flexible lighting effect for the home, discotheque, or shop 28

DIGITAL LEAF by J. S. Haggis

Grow better greenhouse plants with this automatic moisture control circuit 32

P.E. ORION-1 by D. S. Gibbs & I. M. Shaw

A high quality low cost 20 + 20W stereo amplifier 46

P.E. MINISONIC-3 by G. D Shaw

Details of the keyboard controller, ring modulator, noise generator, h.f. detector and
oscillator, and power amplifiers 58

GENERAL FEATURES
SURFACE ACOUSTIC WAVES by T. S. Fisher
Is this the technique of the future? 41

INGENUITY UNLIMITED
Sound -to -Light Modulator-Serial Connection Multivibrator 66

NEWS AND COMMENT

EDITORIAL-The Triumphs of Radio Astronomy 27

SPACEWATCH by Frank W. Hyde

Mercury Again-More From Skylab 37

NOBEL PRIZE FOR CAMBRIDGE RADIO ASTRONOMERS by Frank W. Hyde 38

ELECTROMUSE by Malcolm Pointon

Electronics and Music 53

THE NEXT DECADE

Final selection of readers' predictions for the future 54

INDUSTRY NOTEBOOK by Nexus

What's happening inside industry 69

MARKET PLACE
Constructional Aid, Tapes, and News Briefs 70

BOOK REVIEWS
Selected new books we have received 73

NEWS BRIEFS
Audio Fair-Link-Up-Price Cut 73

READOUT
A selection of readers' letters 74

Our February issue will be published on Friday, January 10, 1975

© IPC Magazines Limited 1975. Copyright in all drawings, photographs and articles published in PRACTICAL
ELECTRONICS is fully protected, and reproduction or imitations in whole or part are expressly forbidden. All reasonable
precautions are taken by PRACTICAL ELECTRONICS to ensure that the advice and data given to readers are reliable.
We cannot, however, guarantee it, and we cannot accept legal responsibility for it. Prices quoted are those current
as we go to press. Publisher's Subscription Rate including postage for one year, Inland £3.25, Overseas £.4.10.
International Giro facilities Account No. 5122007. Please state reason for payment, "message to payee".

Practical Electronics January 1975

 Celestion °Mon 66 £205.75
TUNERS Celestion Hadleigh E39.25
Goodman. Dimension 8 [127.95
Please add £1.05 for P. 8 P. Int Goodman. Havant SL £44.95
Amstrad MLX 3000 (21.25 Goodmns Mgisters £107.75
Eagle AA8 [47.50 Goodmans Magnum K2 SL (95.65
Eagle TST 152 C32.95 Goodinans Minster £3400
Metro -Sound FMS 20 Mk II C33.35 Goodman. Mezo 3SL [67-35
Teleton 1300 £59.35 Marsden Hall 0110/C NIP £31.95
Teleton ST202 £34.110 Marsden Hall XL15F,C NIP £3929
FANTASTIC OFFER Thorens TE)125AB Mk II [111 95 Sinclair 2000 £29.95 Marsden Hall XL2OF C N P £44.25
Thorens TD160 ABC £6465 Sinclair 4000 £37.45 Marsden Hall XL3OPC NiP £67.50
GARRARD SP25 Mk. IV Thorens TD165 ABC £5395 Wharfedale Denton 2 232.25
PLINTH AND COVER Transcriptor Saturn with Vestigal
TUNER/AMPLIFIERS
Wharfedale Dovedale
Wharfedale Glendale
EA5.75
(311.75
Garrard SP25 Mk IV Arm £63.95
deck Goldring G800 Premise add £1.21 for P. A P. A Ins.
Cartridge Teak fin-
Amstrad 5000
Goodman Module 90
E56.95
[9290
AMSTRAD IC2000 Mk. II
ished Phnth Cover AMPLIFIERS Goodman. 1-10 Module E110.50 STEREO SYSTEM
Inon hinged) All Goodman. 120 Amstrad 102000 Mk II with increased power
Leads Pleas* add £1.05 for P. 8 P. a Inc E113,95
Amstrad Integra 4000 Mk II £25.75 25 k 25W amplifier Complete with a pair
GLOBAL'S PRICE £1995 Amstrad 1C2000 Mk II £31.95 CARTRIDGES of Amstrad Acoustra 2500 speakers
Carr 8 Ins Cl 93 Amstrad 8000 Mk Ill (16.50 Garrard SP25 Mk IV deck G800 Cart
Eagle AA4 E43.10 Ph." ledd 12p for P. A P. In. 4347
Plinth Cover {non hinged) All leads
Eagle AA6 (51.25 Goldring G800H
TURNTABLES Metro -Sound ST2OE Mk II E211.95 Goldring G800E E1-20
E3.40
GLOBAL'S PRICE £80.75
Goldring G800 Carr 8 Ins C3 30
PM.," add £1 05 for P. AP. I Ins Metro -Sound ST40 £34.25 Shure V15 Type 3 £21-40
Metro -Sound ST60 £44.75 Shure M75EJ Type 2 (7-90
Garrard SP25 Mk IV Chassis £12 95
Garrard 86SB P C Cart (Mod) E47.50
Sansu, AU101 P.O.A. Shure M75ED Type 2 £11-10
£1.20
STEREO HEADPHONES
Sinclair 2000 £26.115 Shure 91ED Ple add 42p for P. & P. A Inc
Garrard 86SB Chassis £2240 Sinclair 4000 (4415 Shure M3D £3.10
Garrard 401 Chassis £33.25 Sonotone 9 TACHD £1 30 Koss ESP 6 £48 85
Telefon GA202 03010 Koss ESP 9 £65 75
Goldring 101 Mk II P C 0800 £23 70 Teleton 0402066 £23.95
Goldring GL75 P C G800 (39.95 Koss K7 11 Red Devil £10 99
Teleton SA0307D [27.20 Koss 6 £11 70
Goldring G175 P C G800 £44 40 SPEAKERS Koss K6/LC 413 25
Goldring GL85 P C £66.95 Add 0.92 P. a P. A Inc per Pair Koss KD 727E £14 90
Pioneer PL 12D P.O.A. Amstrad 1500 [25.65 Koss 747 419-75
Sansui SR 212 P.O.A. COMBINATION UNITS Amstrad 2500 [29'55 Koss HV1 1A NIP £20 95
Thorens TD125 Mk II £73.75 Please add £1.10 toe P. &P. & Ins. Celestion County E46-25 Koss HV1, LC A N P 424 60
Celestion Dimon 10 Mk II (42-45 Koss PRO 5/LC 429 15
Goodmans Compact 80 (Teak) (131 -15 Celestion Dillon 15 M.50 Kos. K7,11 Black 49 90
Goodmans Compact 90 E169.99 Celestion Dillon 25 (132- SO Sonnhelser HD414 [10.75
Goodmans Compact 1-10 (Teak} 091 -00 Celestion Dillon 44 410995 Sennheiser HD424 015 55

=Ern:I LONDON 1=10 HP FACILITIES

O Please Nate Erem effort is

Shceninq Centre
1536 Coventry Road. Ynidley
Tel 021 706 9949
328 Edgware Road W2
Tel 01 262 3847
246 Pentonville Road. N1
Tel 01-837 5535
12 London Road North End
Tel

=an
0705 68321
AVAILABLE TOR
PERSONAE CALLERS ON,
MAIL ORDERS
TO 174PENTONVItir
ROAD LONDON NI

AUDIO'
made ru ensure sites listed ale 4 High View Parade 120 Notting Hill Gale Vsl 46 Market P1.111
Tel
Order with confidence
401,411 el lime or going to press Redbridge Lane East Tel 01 229 1437 0734 595331
Send Postal Order.
bur are suerect in alterainui Woodford Avenue Illord 50 Stamford Hill 516 WATFORD Cheque, Money Order.
without prior polite -16011 Tel 01 550 1086 Tel 01-806 4699 105 St Albans Rd lel 391132 Bank Dials. Giro or
Cash by Reg. Mail
FULL 12 MONTH AFTER SALES SERVICE
We give a FULL 12 MONTH GUARANTEE on all NO HIDDEN PRICES AT GLOBAL PERSONAL CALLERS VERY WELCOME!
PLEASE NOTE All Cheques.
Money Orders Postal Orders,
oroddcs purchased at any branch parts and labour AUDIO - ALL OUR PRICES ARE COMPARE OUR PRICES WIN ANY IN 1111 800RI Bank Draft Of Vito to be
aDso e', FREE SHOWN WITH VAT INCLUDED OPIT1 MONO. TO TATuROPT 910 am 6 ork made poydble to
1001.116113. OPIN OMIT 1 pro
MAOTOMEAD LTD

*ELECTRONIC
PIANO KIT I 4
Phoenix

Ji
.41.214,,,.....4,
*SYNTHESISER
r--,,,,, , , - .. ''"'olfr'APir- -'
..
_
Electronics
KIT
(Portsmouth) Ltd.
*ELECTRONIC 139-141 Havant Road,
Drayton, Portsmouth, Hants
ORGAN KITS
P06 2AA
There are five superb Elec-
tronic Organ kits specially Full member of AFDEC--the industry's association of
designed for the 0 -I -V en- franchised electronic component distributors.
thusiast. With the extreme
flexibility allowed in design. Our prices include VAT at the current rate -and
you can build an organ to your requirements. carriage on all goods is free.
which will compare with an organ commercially built
costing double the price. Send for our catalogue and price list -we'll mail that
*Portable organ with 4 octave keyboard. £145.29. * Console organ to you free, too.
with 5 octave keyboard. (269-90. *Console organ with 2 x 4 octave
keyboards and 13 note pedal board. £47065. *Console organ witn THIS MONTH'S BARGAIN OFFER!
2 . 5 octave keyboards and 32 note pedal board. £665. *Console organ Small signal silicon transistor kit -5 each BC108,
with 3 v 5 octave keyboards and 32 note pedal board. £770- *WAN
Sound Synthesiser Kit. £130. *W/W Touch Sensitive Electronic Piano. BC178, BC205, BC208, BFY51, ME1120, ME8003,
£100. 2N2924, 2N2926, 2N3394, ACY28.-Catalogue value £7.
All components can be purchased separately, i.e.. semiconductor Bargain pack PEP2A, £4.90.
devices. M.O.S. master oscillators. coils, keyboards. pedal boards.
stop tabs. draw bars. key -contacts. etc.
Send 50p for catalogue which includes 5 . 10p vouchers or send your
own parts list. enclosing S.A.E. for quotation. Please send your catalogue -free!
E LV I N S Name
ELECTRONIC MUSICAL INSTRUMENTS Address
Designers and component suppliers to the musical industry.
12 Brett Road. Hackney, London, E8 1JP. Tel. 01-986 8455. PEP 1A

2 Practical Electronics January 1975

 MODEL C7202EN MODEL C7208FM
20.000 o.p.v. DC. 30.000 opv DC.
10.000 o.p.v. AC 15.000 opv AC.
Mirror Scale. 6/3/15/60/300/600/
5/25/50/250/500/ 1200V. DC.6/30/
1000/2500 V. DC. 120/600/1200 V. AC
10/50/100/500/1000 DC Resistance x 1.
V. AC. DC Resistance x10. x100. x1000
x10, x1000(301] 15011 centre scale)
centre scale) DC DC Current 30)1A/
Current 60uA/ 3/30/600mA. -20 to +63dB
2 5mA/250mA. -20 OUR PRICE £8.95 P & P 30p
to +68dB.
OUR PRICE £6.50 P & P 30P MODEL U4311 Sub -standard
KAMODEN HM720B FET VOM Multi -range Volt -Ammeter
Sensitivity 330
Input impedance 10 Ohms/Volt AC
Megohms. Ranges and DC.
0/.25/1/2.5/10/50/ Accuracy 0.5%
1000V DC. 0/2.5/10 DC. 1% AC.
50/250/1000V AC. Scale length:
0/25uA/2.5/25/250 165mm.
mA DC. 0/300/750krA/
0/5k/50k/500k/5 M 1.5/3/7.5/15/
500 Megohms 30/75/150/300/
OUR PRICE 750 A/1.5/3/
P & P 40p 7.5A DC. 0/3/
£21.00 7 5/15/30/75/

and make no mistake

TMK 200 MULTIMETER KIT U4323 MULTIMETER MODEL 500
KAMODEN 360 MULTIMETER
Hqh sensitivity.
DC 100kohmN
AC 10kohmN
5" mirror scale,
overload protect.
150/300/750mA/
1.5/3/7.5A AC.
0/75 /150/300/750mV/1.5/3/7.5/15/
30/75/150/300/750V DC. 0/750mV/
1.5/3 /7.5/15/30/75/150/300/750V
AC. Automatic cut out device. Supp-
lied complete with test leads, manual
20,000opv. Simple 30.000 opv with ed. Ranges: 0.5/ end test certificate.
Build yourself a unit with audio/IF 2.5/10/50/250/
overload protect.
quality 20000 opv oscillator. Suitable tion. Mirror wale. 1000V DC. 5/10/ OUR PRICE £52.00 P&P 50p
ultimeter and for Reneral receiver 0/0.5/2.5/10/25/ 50/250/1000V
see money. tuning. Ranges: 100/250/500/ AC. Current: MODEL AF.105 VOM
Complete kit with 0.5/2.5/10/50/250/ 1000V DC. 0.01mA/0,5/5/50/ 60,000 opv. Mirror
meter scale, 500/1000V DC. 0/2.5/10/25/100/ 500mA/10A. scale. Meter
movement and 2.5/10/15/250/500/1000V AC. 0.05/ 250/500/1000V Resistance: 0.1/
0.5/6/60/500mA DC. Resistance: AC. 0/50uA/5/50/ 1/10/100 ohms/ protection.
rotary range 500mA. 12A DC. 1/10/100k ohms/ 0/3/3/12/60/120/
elector ready x 10, x 100. x 1,000, x 10.000 (50f).
500f), 5kf1, 501.0 centre scale) 0/60k/6 meg/60 megohms. 10/100M ohms. 300/600/1200V DC.
mounted in Battery operated. Size: 160 x 97 x Decibels -20 to 0/6/30/120/.
cabinet. All parts, OUR PRICE £13.95 Carr. paid +62dB. Battery operated. Size: 180 x 300/600/1200V DC
40mm. Supplied in carrying ease Com- Case for above E1.75
batteries, test prods and plate with teat leads. 140 x 80mm. Supplied complete with, 0/304A/6/
instructions. Ranges:0/0.6/6/30/ test leads etc. 60/300 rnA/
120/600/1200V D.C. 0/6/30/120 OUR PRICE £7.70 P&P30p
P&P40p
HIOKI 750X VOLT-OHM- OUR PRICE £17.60 12 Amp. 0/10K/
600/1200V A.C. Current 0/0.6/6/ 1m/10m/100
60/600mA. Resistance:0/10/ HIOKI 730X MILLIAMETER TMK MODEL 117 FET Meg Ohms.-20to.17.113.
100K/1 /10 Meg ohms. Decibels: 30,000 opv. Over- 43 renges: 0-0.3/0.6/
1.5/3/6/12/30/60/150/ ELECTRONIC VOLTMETER OUR PRICE £12.50 PAP 30p
-20 to +63db. Size: 90.150 x load protection. 300/600/1,200V DC. Battery operated.
36mm 6/30/60/300/6007 0-3/6/15/30/60/120/ 11 Meg input 26 LB3 TRANSISTOR TESTER
OUR PRICE E7.95 P&P 30p. 1200V DC.12/60/ 300/600/1,200V AC. ranges. Large 4Y." Tests ICO and B.
120/600/1200V AC Currant: 0-30/60uA/ or scale. SWe: PNP/NPN. Operates
60/pA/ 1.5/3/15/30/150/300 149x 117x6Omm. from 9V battery.
AUDIOTRONIC Model ATM1 30mA/300mA. mA/6/12A. Resistance: 0.3-12000V DC. Instructions supplied
2K/200K/ 0-3/300k/3/30Mohms. 3-300V RMS AC. OUR PRICE
p pot molt i-
oTrnop value
2 Meg Ohm. Decibels: .-10 to +17dB. Output: - 8-600V P.P.
0 -3/6/15/30/60/120/300V. Accur- DC current 0.12- £3.95 P&P 20p
63dB.
-Metes acy t 3% DC,S 4% AC. Sensitivity: 12mA. Roisterer
volt AC and DC. OUR PRICE £7.50 50,000 opv DC, 5,000 opv AC.4 inch up to 2000MOhms. Decibels: -20 to LB4 TRANSISTOR
DC current 0-1mA/ PAP 30p meter. Built in protection. Size: 57 x .51dB. Supplied complete with leads TESTER
100mA. Residence 102 x 153mm. and instructions. Tests PNP or NPN
0/150k ohms. U4324 MULTIMETER OUR PRICE £11.95 P&P 40p OUR PRICE £18.50 P&P 200 transistors. Audio
Decibels: -10 to High sensitivity, over. 'ndication. Operates
.22dB. Size 90 x TMK 100K LAB TESTER on two 1.5V
60 x 28mm. anger TMK MODEL TV1150K batteries. Complete
Complete with 20 100,000opv. 6%" with instructions etc.
test lead. 0A/1.2/ 7113 46 ra mirror wale. Buzzer
60/120/600/1200V scale. 50knges. /V DC short circuit check. OUR PRICE
OUR PRICE E3.25 P&P 15p DC. 3/6/15/60/150/ 50k/V AC. Sensitivity 100,000
300/600/900V AC. DC Volts: 0.125/ opv DC. 5k/V AC
4.50 P&P 20p
Current: 0.06/0.6/ 0.25/1.25/2.5/5/10/ DC Volts: 0.5/2.5/
6/60/600mA/3A DC. 25/50/125/250/ 10/50/250/1000V
KAMODEN Ti35
AUDIOTRONIC Model ATM5 0.3/3/30/300mA/ 500/1000. AC Volts TRANSISTOR TESTER
Jewel movement, AC. 3/10/50/250/
3A AC. Resistance: 1.5/3/5/10/25/50/ 500/1000V DC. High quality
attractively moulded 25/500 ohms/0.5/5/50/500k ohms/5 125/250/500/ current 10/100uA/ instrument to
case with edgwise Mohr.. Decibels: -10 to +12dB. Size 1000. DC current 10/100/25110A. Reeiatence: test reverse leak
ohms adjustment. 167 x 98 x 63mm. Supplied comp- 25/50uA/2.5/5/25/ 1k/10k/100k/10 Meg/100 Meg ohms. current and DC
Re 0.3/15/150/ lete with test leads, spare diode and 50/250/500mA/5/
:

300/1200V AC, Decibels: -10 to +49dB. Plastic case current. Ampli-

(2500 opv). 0-6/30/
instruct... 10A. Resistance: with carrying handle. Size: 190 x 172 fication factor of
OUR PRICE £9.25 P&P 30p
10k/100k/1 Meg/ x 99mm. NPN, PNP, diodes,
300/600V DC, 10 Meg ohms. -20 to +81.5dB. transistors, SCR's
15000 opel. 0-300 OUR PRICE £19.95 P&P 30p etc. 4" square
LIAM-300mA DC. OUR PRICE £12.50 P&P 20p
Resistance: x 10 & U435 MULTIMETER 370WTR MULTIMETER clear scale mater.
x 100. -10 to +16dB. Operates from
20,003o.. Ranges: Features AC current internal batteries.
Supplied with battery HIOKI MODEL 700X ranges. 20,000opv. Complete with
test leads and data 75mV/2.5/10/25/ 100,000opy. Overload 0/0.5/2.5/10/50/
booklet. Size: 121 x 73 x 29mm. 100/250/500/1000V instructions, leads
DC. 2.5/10/25/100/ protection. Mirror wale. 250/500/1000V DC. carrying handle.
OUR PRICE £3.95 P & P 20p 250/500/1000V AC. 0.3/0.6/1.2/1.5/3/6/ 0/2.5/10/50/250/
12/30/60/120/300/ 500/1000V AC. OUR PRICE £17.50 P & P 40p
C a t 50uA/1/5/
25/100mA/0.5/2.5A 600/1200V DC. 0/500A/1/10/100 U4341 Multimeter &
MODEL TH12 DC. 5/25/100mA/ 1.5/3/6/12/30/60/150/ mA/1/10A DC.
20-000 opv. Overload 0.5/2.5A AC. Resist. 300/600/1200V AC. 0/100mA/1/10A Transistor Tester
protection. Slide switch ace: 0.3/3/30/300k 15/30AA/3/6/30/60/ AC. 0/5k/50k/500k/ 27 ranges. 16,7000pv.
selector. 0/0.25/2.5/10/ ohms. Size: 205 x 110 x 84mm. Sup- 150/500mA/6/12A DC. Overload protected.
50/150/1000V DC. 0/10/ plied complete with leads, crocodile 2k/200k/2M/20MOhms. RrecM7ItI5s? Mato +62dB. Ranges: 0.3/1.5/6/
50/250/1000V AC. 0/ clips and steel serving case. -20 to +63dB. OUR PDICE £19.95 30/60/150/300/900V
P&P 30P DC 15/75/30/150/
50uA/25/250mA DC. OUR PRICE £8.75 P&P 3 p OUR PRICE £14.95 P&P30p
0/3k/30k/300k/3 Megohms. -20 to KAMODEN 72.200 Multitester 300/750V AC.
50dB. Current: 0.06/0.6/
U4312 MULTIMETER Model HT100B4 MULTIMETER High sensitivity 6/60/600mA DC.
OUR PRICE £5.95 P&P 30p extremely sturdy tester. 200,000 opy 0.3/3/30/300mA AC.
Overload protected, Overload protected.
t t shock proof circuits. Resistance: 0.08/
Mirror scale. 0.6/2/6/20/60/200k ohms/2 Mohms.
general electrical 9.5uA Meter with Ranges: -0/.06/.3
HIOKI 720X VOM use. 667opy. mirror scale. Sensitivity Battery operated. Supplied complete
A versatile. 0/0.3/1.5/7.5/30/ 3/30/120/600/ with probes, leads and steel carrying
100kV. Polarity change 1200V DC. 0/3
accurate measure 60/150/300/600/ switch. Rang.: 0.5/2.5/ case. Size: 115 x 215 x 90rnm.
ing instrument. 900V DC & 75mV. 12/60/300/11200
1./50/250/500/1,000 V AC. 0/6uA/ OUR PRICE E10.50 P&P 30p
20,000 opv. 0/ 0/0.3/1.5/7.5/30/ Volts DC. 2.5/10/50/ 1.2mA/120mA/
5/25/100/500/ 60/150/300/600/ 250/1,000 Volts AC. 600mA/12A DC S100TR MULTIMETER
1000V DC. 0/10 900V AC. 0/300uA/ DC resistance' 0-20/ 0/12A AC. -20 to
50/250/1000V 1.5/6/15/150/60/ 200k/2/20 Meg. ohms. +63dB. 0/2k/200k/ TRANSISTOR TESTER
AC. 0-50uA/ 600mA/1/1.5/6A DC current:- 10/250uA/2.5/25/250 2 Meg/200 100,000opv. Mirror
250mA. 0-20k/ DC. 0/1.5/6/15/ mA/10A. AC errant -0-10A. -20 wale. Overload
2 Megohms. 60/150/600mA/ to +62dB. Operates from 2 x 1.5V OUR PRICE f22.50 P&P 30p protection. 0/0.12/
OUR PRICE 1.5/6A AC. 0/200/3k/30k ohms. DC batteries. Size: 180 x 134 x 79mm. 0.6/3/12/30/120/
accuracy 1%. AC 1.5%. Knife edge U4317 MULTIMETER 600V DC. 0/6/30/
£5.97 pointer, mirror wale. Complete with OUR PRICE E17.50 P&P 40p High sensitivity 120/600V AC.
P&P 30p sturdy metal carrying case, leads and nst ument for field 0/12/6000A/12/
instructions. and laboratory work. 300mA/6/12A DC
MODEL AS.1000 VOM Knife edge pointer. 4111 0/10k/1 Meg/
OUR PRICE £10.25 P&P 50p 100,000 opv. (06mm. mirror scale. -="-- 100 Meg.
MODEL PL436 Mirror scale. Overload Omprotectionl -20 to +50dB.
20.000 opv DC. U91 Clamp VOLT Built-in meter 0.01-0.2 MFD
8000 opv AC. AMMETER protection. 0/3/ Ifl.a5Md0/257/5/0/100/250/500/1000 Transistor tarter manures Alpha, Beta
Mirror scale
6/3/12/30/120/
600V DC.3/30/
ErM For measuring AC volt-
age and current without
breaking circuit. Ranges:
12/60/120/300/
600/1200V DC.
0/6/30/120/300/
V DC. 0.5/2.5/10/25/50/100/250/
500/1000V AC. Current: 50uA/0.5/
1/5/10/50/250mA/1/5A DC. 0.25/
and ICO. Complete with instructions,
batteries and leads.
OUR PRICE E19.95 P&P 25p
300/600V AC. Current: 0.5/1/5/10/50/250mA/1/5A AC. Res-
120/600V DC. 600V AC. 0/10pA/ 0.5/10/100/200 ohms/1/3/
60/6009A/60/
600mA.
10/25/100/250/500A.
Accuracy 4%. Size 283 x 6/60/300mA/
12 Amp. 0/2K/
istance:
30/300k ohms. Decibels: -5 to .10dB
Battery operated. Size: 210 115 x
ALL PRICES
10/100K/1 Meg/10 Meg Ohm.
20 to 46dB.
94 x 36mm. Complete
with carrying case, leads
and fuses.
200K/2M/200 Meg
Ohm. - 20 to . 17dB.
9Ornm. Supplied in carrying case com-
plete with leads. EXCLUDE VAT
OUR PRICE £6.97 1%1.30p OUR PRICE £13.50 P&P 30p OUR PRICE £17.50 PAP 30p. OUR PRICE £16.50 P&P 40p Also see following pages

3
Practical Electronics January 1975
 SWR METER Model SWR3 WALKIE TALKIES EA41 REVERBERATION SPECIAL OFFER! SAVE OVER 50% TE1021 Stereo Listening Station
Handy SWR meter for SW/FON NV7 For balancing
transmitter antenna align Super low cost
AMPLIFIER and gain selection
ment, with built-in field Self contained, of loudspeakers
transmitter transistorised, with additional
strength meter. Accuracy receivers. 100MW
5%, Impedance 52' Indic- battery operated. fwiliphone
ty for stereo
ator 100uA DC. Full with call buzzer and Simply plug in he ad
scale 6 section collapsible on %off volume microphone, guitar etc. and output to switching. Two
antenna. Size 145 x 50 x ontrol. 7 transistors. your amplifier. Volume control and AMSTRAD 8000 2 Stereo amplifier gain controls. speakers on -off slide
60mm. Telescopic rod Satia depth of reverberation control. Beau' 7 watts per channel rms. Inputs switch; stereo headphone socket.
antnna walnut cabinet. 184 x 77 x 108mm. for tuner tape. phone. Headphone OUR PRICE E2.25 P&P 15p
OUR PRICE £4.25 P&P 30p
OUR PRICE E7.50 socket. List price E29.98.
P&P 30p
OUR PRICE E28.95 AUDIOTRONIC
Per PAIR P.&P 50p.
OUR PRICE f12.95 P & P 60p
C15 PULSE OSCILLOSCOPE LOW NOISE CASSETTES
For display of pulsed NOT LICENSABLE SPECIAL PURCHASES! SPECIAL OFFER! CONVERT YOUR TYPE 5 10 25
and periodic wave- IN THE U K RECORD DECK PACKAGE STEREO SYSTEM C60 Cl 67 E3.00 £7.08
forms in electronic C90 E2.24 E4.25 E10.00
circuits. VERT. AMP. MODEL MG100 SINE SQUARE by Famous Manufacturer TO 4D SOUND C120 E2.73 E5.17 £12.24
Bandwidth: 10MHz. IFEJWAVE AUDIO GARRARD SP25 Mark 111 with FOR UNDER f16 P&P 3p each 10 and over Post Free
Sensitivity at 100kHz G800 cartridge in luxurious plinth
VRMS/mm: 0.1-25; GENERATOR with cover MP7 MIXERPREAMPLIFIER
HOR. AMP. Band. Range 19
width: 500kHz. OUR PRICE £13.95 p & P 75p 5 Microphone
220.000Hr Sine GARRARD SP25 Mark 111 Record inputs each with
Sensitivity ay 100kHz individual gain
VRMS/mm: 0.3-25 Wave 19 -100.000 Hz Square Wave deck fitted KS 40A cartridge
Preset triggered sweep Output Sine or Square wave 10v P to P controls enabling
Sire 180
OUR PRICE f9.95 P & P 50p complete mixing
1-3000usec. Free running 20-200 x 90 90mm Operation
kHz in nine ranges. Calibrator pips 220 240v A C Exclusive offer of GOODWIN 4 facilities. Batten/ operated. Size: 235
220 x 380 x 430mm. 115-230V AC. CHANNEL CONVERTER and a pair x127 x 76mm. Inputs: Mica. 3 x 3.11V
OUR PRICE £19.95 P&P 60p LHO2S STEREO HEADPHONES 50k; 2 x 3mV 600 ohms. Phono. Mag.
OUR PRICE E43.00 Carr. paid L ght e-ght head. of ADIS 10 watt 8 ohm bookshel 4mV 50k; Mono Ceramic 10OrriV 1
POWER RHEOSTATS phones with padded speakers enables you to add 4D Meg. Output 25OrnV 100k.
High quality ceramic ear pieces.pieces. 4/16 ohms sound to your existing system
Complete eh s' pi OUR PRICE f8.97 P&P 20p
RUSSIAN C116 Double Beam
OSCILLOSCOPE
construction. Wind.
ings embedded in
20-20,000Hz.
Complete with 6' 4 act.
details Normal retail value £25.60
AUDIOTRONIC AHA101
5 MHz pass band. vitreous enamel. lead and plug.
Heavy duty brush OUR PRICE f15.110 p & P Et. Stereo Headphone Amplifier
Sap Y1 and Y2
amplifiers. Rectang- wiper. Continuous GOODWIN CONVERTER available All silicon,
ular 5" 4" CRT. rating. OUR PRICE £1.97 P&P 30p separately E3 95 P & P 60p transistor
Calibrated triggered Single hole fixing. 'A" diameter shafts. a Olio °per
sweep Bulk quantities available. DHO2SSTEREO HEADPHONES Model A1018 totes from meg. /
milli-sec/cm. Wonderful value FM TUNER ntic, ceramic
9Free running time 25 WATT 10,25/50/100/600/1000/ and excellent or tuner
6 transistor high
e, 1fi
Built-in time base
2600 ohms. £1.15 P&P 10p performance quality unit - inputs with
twin stereo headphone outputs and
combined. Adjust- 3 IF stages and
Calibrator nd amplitude Calibrator. 50 WATT 10/50'100(250/500/ able head band. double tuned se volume controls for each
Supplied complete with all accessories
and instruction manual.
1500'5000 ohms.
£1.62 P&P lop
Impedance 8 ohms.
20-12,000Hz.
discriminator. -- -

For use with most amplifiers. Covers

channel Operates from 9V battery.
INPUTS: 5friV and 100mV.
Complete with 88-108MHz. Powered by 9V battery. OUTPUT: 50InV per channel.
OUR PRICE £87.00 Carr. paid 100 WATT 1 '6/10/25/50/250/506/ Nike,
2500 ohms
lead and plug. OUR PRICE £13.50 P&P 30p OUR PRICE E8.50 P&P 30p
MODEL TE15 £2.34 P&P 15p OUR PRICE £2.25 P&P 30p Stereo multiplex adapter E5 95 extra. HIGH QUALITY
GRID DIP METER ELECTRONIC CALCULATORS C-AAv CONSTRUCTION
Transistorised. Open.
EMI LOUDSPEAKERS 7E1035 Stereo HEADPHONES JOSTY KIT KITS
etas as Grid Dip. Model 350 13 x 8" with Low cost with exc
Oscillator, Absorb - single tweeter/crossover. ellent response. Foam WE ARE APPOINTED
lion /Neve Meter and 20-20000Hz. 15 watts rubber earcups. Adjust-
STOCKISTS AT
Oscillating Detector. RMS. Available 8 or able headband. 8 ohms
Frequency nge 15 ohms. impedance. Frequency Oxford Street( 42 &
440k H1-2MMHz response 25Hr - 18k Hz. 257 Tottenham Court Road.
OUR PRICE Complete with cable 34 Lisle Strom 162, Fleet Street.
in six coils_ 500s1A .

meter. 9V battery £7.50 each P&P 37p and stereo jack plug. 311 Edgware Road. CROYDON
operation. Size: Model 450 13 x 8" with OUR PRICE £2.60 P&P 30p BIRMINGHAM KINGSTON
100 x 80 x 40rnin. twin tweeter/crossover. LEICESTER NORTHAMPTON
OUR PRICE £17.50 P&P 30p 55-13,000Hz. 8 watts SOUTHEND TUNBRIDGE WELLS
RMS. Available 8 or 15 ohm SDH8V MONO/STEREO
HEADPHONES WOLVERHAMPTON branches. or
OUR PRICE £3.62 each P&P 35p We carry a tremendous range of by Mail Order.
TRANSISTORISED L.C.R. Volume control for
SPECIAL PURCHASE each channel. 4/16 ohms both pocket and desk calcula- All kits are complete with corner*
BR/13 MEASURING BRIDGE impedance. Frequency tors from as little as £9.90
A new portable honsisie easy to follow instructions and
LIMITED QUANTITY, response 20Hz-18k Hz. Owing to the demand it is not covered by full guarantee.
bridge offering Tannoy12"DR,11 Complete with 10ft. possible to include them in this
excellent range and coiled lead and jack plug. Post and Packing 15p per kit.
accuracy at low Bass Speakers advertisement. so send for our
OUR PRICE E4.97 P&P 30p latest price list or call into any AF 20 Mono amplifier £5 51
cost Resistance:
.4,0 8 ohms 30 wan branch AF25 Mixer £3.29
6 ranges' 0.1 Heavy duty, ideal AF30 Mono pre -amplifier El 20
ohm -11.1 rnegohm 1% Induct- for HiFi P A. BH001 HEADSET and Boom MINIATURE ORGAN AF35 Emitter amplifier Er 42
ance: 6 ranges' 1 microhenry-111 Group. Microphone A F 80 0.5W mic. amplifier Ea ge
henries z 2% Capacity: 6 ranges: Moving co.l. Ideal MUSIC MASTER AM100 AF305 Intercorn....... .. E7 67
OUR PRICE £12 60 AF310 2 Mono Amplifier E7 55
lOpf-1110 mfd z 2% Turns Ratio: P&P 50p for language Spanning
teaching, nearly two M160 M lti vibrator £216
6 ranges: 1:1/1000-1:11100 c 1% comrnuni M1302 Transistor tester Ell 33
Bridge Voltage at 1.000cps. Opera- octaves. M191 VU Meter
PS200 Regulated POWER cations etc.
including
£5 37
ted from 9 -volt battery. 100 micro - Headphone impedance 16 ohms. Mic- M192 Stereo balance meter._ £5 93
amp meter indication. Size 7i- x SUPPLY UNIT semi-
Solid state. Variable rophone impedance 200 ohms. L F380 Quadraphonic device. E e 42
5' 2" tones. An Automatic light control f:3 75
OUR PRICE E25.00,ps p son output 5-20V DC OUR PRICE £5.95 P&P 30p This instrument
up to 2 Amp. Ind.- A730 Photo cell switch unit. 6 66
pendent meters to will give hours of enjoyment AT50 400W triac light
TE-200 RF SIGNAL monitor voltage and [s.. HANIMEX HRC 3075 to all the family. Beautifully dimmer/speed control E 5 18
current. Output CASSETTE RADIO finished. The Keyboard range can AT56 2.200W triac light
GENERATOR 220/240V AC. be adjusted to be in tune with any dimmer/speed control E 6 75
Accurate wide wage Size: 1900 136 x Covers instrument. Op. from AT60 1 channel light control £10 52
signal generator 98mm. Medium and internal 9V battery. Fitted with AT65 3 channel light control £ 16 52
covering 120 kHr-500 FM wave - on:off switch, vibrato switch. GU330 Tremolo unit Le 10
OUR PRICE £19.95 P&P 50p HF61 Diode detector . ........ E387
MHz on 6 bends b nd SI'd earphone socket and external
Directly celibates. AUDIOTRONIC LE -102A volume and FIF65 FM transmitter._ 1E3 21
9V D C socket. HF75 FM receiver E366
Variable R F. INTERCOM tone controls. HF310 FM tuner E 16 32
attenwtor audio output, Oral socket Battery -Mains OUR PRICE £7.95 P&P 50p HF325 Deluxe FM tuner E28 33
for calibration. 220 -240V .c. operation. Will record HF330 Decoder IHF310/325/ lei 55
Brand new with instructions. direct from radio or through built BINATONE DIGITAL CLOCK GP310 Stereo prearnplif ler
Sire 140mm x 216irim 170mm in condenser microphone. Corn Attractive for use with 2 x AF310 £22 98
OUR PRICE £17.50 plate with batteries. earphone. ivory cage. GP312 Circuit boind E1002
P&P 50p Large clear GP304 Circuit board E5 33
and cassette.
numbers for HF380Iw/vhl aerial amplifier £5 02
TE22 SINE SQUARE WAVE OUR PRICE1f2430 P & P 50p hours. minutes HF395 broadband aerial amp. E2 10
AUDIO GENERATOR Beauticuirci made and finished in d. NT10 Stabilised power supply
100mA, 9V
Sine 20cps two tow ivory buff, the LE -102A SPECIAL BARGAIN !! A C. 240V operation
N7300 Stabilised p. supply
E8 27
Ell 16
to 200kHz useful in the home, office or shop STEREOSOUND SPEAKERS Size approx. 61 it 3 x 3; inches.
NT310 Power Supply 240 V AC
on 4 bands. and is suitable for use. baby Matched pair of OUR PRICE £4.50 P&P 60p or 2 18 V D C at 2 amps C554
Square 20 alarm. Wall or desk mounting stereo bookshelf
NT305 Voltage converter £ 5 54
FA 1030 57rnm speaker mic gives clear 2 - speakers. Deluxe SINCLAIR ICI2
Otpu teak veneered NT315 Power supply 240V AC
way communication with orcoff finish. Size: INTEGRATED to4,5/15V DC, 500mA £12 06
500 Odacrils
and volume control on master 368 x 229 x
unit. Operates on 9V batt. Approx CIRCUIT Amateur Electronics by Josty.K.,
200/250V 190mm. 8 ohms. the professional book for the amateur
AC operation. Supplied brand new 60ft lead B watts RMS, 16 AMPLIFIER c
' \.,4110\gi,71;
watts peak.
-covers the subieet from basic Prie-
guaranteed. with instruction manual OUR PRICE f3.95 P P 30p
complete with - opals to advanced electronic techniq
end leads. Complete with printed circuit ces. Complete with circuit board for
D ad.
OUR PRICE £24.95 P&P 50p TRITON 4318 PORTABLE
I
mounting board AE1 to AE 10 listed below.
8 TRACK CARTRIDGE OUR PRICE £1.50 P&P 15p OUR PRICE E3.30 (No VAT/
ARF 300 AF/RF SIGNAL OUR PRICE f12.95PAIRP&P SOO P&P 25p plus VAT.
PLAYER WITH MW/LW SINCLAIR Project 80 Modules
GENERATOR RADIO ZOO Power Amp. ES 95 P P 15p AE1 100mW output stage C1 55
All transistorised FM TUNER CHASSIS Z60 Power Amp. E745 P P 15p AE2 Pre.ampl if ler C 32
compact fully Will play 8 6 transistor Stara° 80 Pre -Arno El 3 95 P 6 P 15p AE3 Diode receiver f 2.06
portable. AF sine - track stereo high quality Active Filter Unit £7.46 P a P 15p AE4 Flasher
tuner. Siz FM Tuner E1.28
wave 18Hz to 220 cartridge E1395 PIP15p AE5 Astable multi vibrator £1 14
kHz. AF square monaurally. only 153 Decoder
SpRtelOrPeoowDesicr ,E58 9955 .1 .6 pe 13: AE6 Monostable multi -vibrator El 11
wave 18Hz to 100k 101 x 63mm AE7 RC generator
Hz. Output Square/ Channel 3 IF stages. P25 Power Supply £8 .96
011 1
P & P MP AE8 Bass filter
Sine wave 10V. selector Double tuned PZ8 Power SunnyP 101. .5E9 Treble titer
f 1 06
£1.05
P -P RF 100kHz to switch Covers discriminator. Transformer for P28 Coos I Sep P
AE10 CCIR filter C I 05
200MHz. Output medium and long wave Ample output to feed most amplifiers. IC 20Stareossine kit tiesPenis,
1V maximum. bands. Volume and tone controls. Operates on 9V battery. Covers 88- P220 Power Supply kit (545 pa fr
220/240V AC operation. Complete Earphone socket. Battery Mains 108MHz. Ready built, ready for use. SINCLAIR Project 80 Packages Also see previous page
with instructions and leads. operation Fantastic value for money.
OUR PRICE E37.50 P&P 50p OUR PRICE f11.95 P P 50p
OUR PRICE £8.95 P&P 20p
steieo %Corm, Adaptor CS 95 extra
2x250 Stereo 80 P25 EIe. 60
2a40 Stereo 80 P26 t31 30
211260iStereo 90 PZ8 £33.551 sail
lap ALL PRICES
EXCLUDE VAT
4
rractical Electronics January 1975
 SEW PANEL METERS ARE STOCKED AT OUR

SEW PANEL METERS 3 LISLE ST., 311 EDGWARE RD.. & 152 FLEET
ST., BRANCHES or order by post.

USED EXTENSIVELY BY INDUSTRY, GOVERNMENT DEPARTMENTS, EDUCATIONAL AUTHORITIES ETC.

Over 200 ranges in stock -other ranges to order. Quantity discounts available. Send for fully illustrated brochure.
'Items with asterisk are Moving Iron CALL INTO YOUR NEAREST
CLEAR PLASTIO MODEL SCI640 CLEAR PLASTIC MODEL MR 65P
type, all others are Moving Coil sine: 86 x 78mm LASKYS BRANCH OR
Size: 85 x 84mm
23.95 SEND COUPON BELOW
23.80 CLEAR PLASTIC MODEL S0830 23.85
23.75 sun: liOx 83mm f 3 230
FOR NEW 32 PAGE
23.70 50uA 24.30 23.75 PRICE LIST
23.65 101:kiA 24.25 50.0-5(NA .. (3.85
200uA (420
50-0-50uA
100-0.100uA..
23.75
23.70 500uA (4.15
100.0.100uA..
500.0.5001A..
23.80
(3.70 CENTRAL LONDON
1mA .. 23.66 50-0-50uA f425 (3.70
5inA .100.11100uA f4.20 481 OXFORD ST.' 01-493 8641
1-0.1mA . £3.7
10mA .. 23.65 /4.10 3 LISLE ST. WC2 01-437 13204
50mA .. f3.85 10V DC 23.66 /4.10 f3.70 3 13.70. 34 LISLE ST. WC2 01-437 9155
100mA f3.88 20V DC .. 23.65 24.10 50mA (370 118 EDGWARE RD. W2 01-723 9789
500mA 23.66 50V DC .. 23.65 (4.10 10V DC .. (4.10 (370 500 AC :: f f310)
2365 /4.10 20V DC .. .. 24.10 193 EDGWARE RD. WI 01-723 6211
lA DC (3.65 300V DC .. 23.70 150V AC .. (3.60 01-723 3271
5A DC (3 65 15V AC .. £3.75 /4.10 50V DC .. .. 14.10 23.70 300V AC .. csao 207 EDGWARE RD. WI
10A DC £3 65 300V AC .. f 3 75 24.10
f4.10
300V DC ..
15V AC ..
..
..
14.10
f420 5A DC .. 23.70 5000 AC .. f 80 311 EDGWARE RD. WI 01-263 0387
5V DC £365 VU Meter 23.90 10A DC .. 13.70 S Meter lmA.. 24.70 346 EDGWARE RD. W2 01-713 4453
10A DC .. (4.10 300V AC .. 24.20 15A DC .. 13.70 VU Meter 13.70 362 EDGWARE RD. W2 01-713 4194
5V DC .. f4.10 VU Meter.. 14.40 13.80 1A AC .. 13.70 01-753 5112
109 FLEET ST. EC4
CLEAR PLASTIC MODEL SW100 13.86 5A AC .. .. f3.70 152/3 FLEET ST. EC4 81.353 1633
Size 100 80mm CLEAR PLASTIC MODEL MR 45P (4.06 10A AC .. .. 2320
Size: so x 50mm 13.70 20A AC .. .. f3.70 10 TOTTENHAM CT. RD. 01437 2232
(4.10 13.20 10V DC -. 13.70 30A AC .. f3.70 27 TOTTENHAM CT. NO. 01436 3715
f4.50 13.15 50mA AC .. 13.70 33 TOTTENHAM CT. RD. 01-636 2603
14.30 84.10 12g 2)2 100mA AC .. 23.70 42/45 TOTTENHAM CT. RD 01-636 0845
50.0-50u A .. £4.50 2000A f330
23.00 60V DC .. (3.70 200mA AC ..
257/5 TOTTENHAM CT. RD 01.580 0670
100-0-100uA.. 24.45
50-0-50uA 13.15 150V DC .. 23.70 500mA AC .. (3.70
14.30
100.0.100u/1_ 23.10
24.30
£4.30 500.0.500uA.. (2.95 BAKELITE MODEL S80 Enlarged Window ESSEX
£4.30 150V AC .. 04.46 f2.96 Size: 80 ri 80rnm
20218
12.96 86 SOUTH ST. ROPIFORD
£4.30 SOOV AC .. (4.45 (4.50
£4.30 VU Meter .. (coo f2as 2446 205 206 CHURCHILL WEST,
50mA .. 22.95 VICTORIA CIRCUS, SOUTHEND 0702612I41
2.96 (4.20
EDGWISE MODEL PE70 22.95 300V AC .. f3 06 50-0-50uA 14.46
Size: 90 x 34mm to DC .. /2.95
12.95
S Mew ImA
VU Meter..
(2 95
23.40
100-0.100uA.. 24.40
/4.20 KENT
£4.15 10VDC /2.95 IA AC .. (2. 5 IA DC .. (420 53/57 CAMDEN RD_ TUNBRIDGE WELLS
24.10 f2.95 5A AC .. (2.95 5A DC .. 1420 0892-23242
24.05 1'2.95 10A AC .. (2 5 24.20
23.90 300V DC .. 22.95 20A AC .. f2 5 1420
50-0-50ta A
100.0.100uA..
.. f 4 10
24.05 15V AC .. 23.05 30A AC .. (2.96 300V DC
300V AC
f4.20
(4.30
LEICESTERSHIRE
(3.86 CLEAR,PLASTIC MODEL MR 38P VU Meter .. 24.70 4S MARKET PLACE. LEICESTER
300V AC 23.95 Site: 420 42mm 0533-5378/8
VU Meter 24.30 CLEAR PLASTIC MODEL MR 52P
(3.10 Sins 60 x 60mm
MODEL ED107 EDUCATIONAL METER (3.05
f 3 00 23.70
NORTHAMPTONSHIRE
Size: 100x 90 150min including terminals 22.85 f3.50 73 ABINGTON STREET,
50-0-50uA £305 500uA 23.35 NORTHAMPTON 0604-35753
A nines of high quelity 100-13.100uA.. £3.00 50.0-50uA .. 23.50
moving coil instruments (3.45
died for school experi 500-0-500uA (2.80 100-0.100uA.. STAFFORDSHIRE
rnents and other bench lmA (2.80 lmA 23.30
appliutions. 3" mirror 1.0-1mA . (280 5mA .. f3.30 30 WULFRUM WAY, WOLVERHAMPTON
scale. The meter move- 2mA . f 2 AO 10mA .. 13.30
0902-23384
ment is .oily accessible 5mA f 2 80 50mA 13.30
to demonstrate internal 10mA (2.80 100mA (3.30
working. 20mA (2.80 500mA 13.30 SURREY
50mA 12.80 20V DC .. 12.80 15 DC f3.30
f8.50 100mA f 2 80 50V DC .. f2.80 5A DC (3.30 S Me er 1mA.. 23.30
27.90 15OrnA (2.80 100V DC .. . 12.80 10V DC (3.30 VU Meter.. f 3 80 1046 WHITGIFT CENTRE. CROYDON
50-0-E4uA 27.90 17 80 200mA 22.80 150V DC .. 12.80 20V DC 23.30 IA AC (3.30 01-681 3027
C7.60 20V DC
f 300mA . £2.80 300V DC (2.85 V DC .. f3.30 5 .. (3.30 17 EDEN ST. KINGSTON 01-5467641
C7.60
50V DC ..
500mA .. (2 80 500V DC .. £2.85 300V DC 23.30 10A AC .. 23.30 .30/40 EDEN ST.. KINGSTON 01-546 1271
17.60
300V DC 27.60 750mA . 1.280 750V DC .. 22.90 15V AC .. (3.40 20A AC . f3 30 12 HILL ST. RICHMOND 01-948 1441
500mA/5A DC (8 .60 lA DC f 2 AO 15V AC .. /2.90 £3.40 30A AC .. f3 30
(7.60 5V/50V DC
£7.60
.. (8.0 2A DC
..
. 12.80 50V AC .. 22.90
5V/15V DC (8.60
11,60 1/6A DC ..
..
08.80 5A DC
104 DC .
(2.80
f2.80
150V AC ..
300V AC ..
(2.90
22a0
BAKELITE MODEL MR 65' Sian: so x eomm WARWICKSHIRE
£7.60 1A/15A DC 18.60 2625
..
3V DC . 12.80 500V AC .. £3 00
24.00' 116 CORPORATION ST., BIRMINGHAM
10V DC (2.80 S Meter lmA.. (2.50 021-236 3603
CLEAR PLASTIC MODEL MR 85P 15V DC (2 80 VU .......(32020 500uA
84.96
(3.66
Ike: 1200 110mm 50.05055 .. 23.95
25.46 23.90 AI 1 FIRAN(Nfl OPE N ISOM
25.40 CLEAR PLASTIC MODEL 50460 100.0-1000A.. 9 no tn opro MON To wit
2635 SI.: 59 x 443mm 500-0-500u A.. f 3 SO
£5.25 (3.60
23.50 /3.60
50.0.50uA (540 (3.45 23.60 OUR CUSTOMER
100-0-1000A.. (5.35 23.40 £3.60
500-0.500uA.. 25.20 (335 £3 60 SERVICES DIVISION al head off ice
25.20 (3.60 3000 DC
50-0-50uA 13.46 100mA (3.60 30V AC .. £3 6U will answer all your enquiries -
1.0-ImA £520 100-0-100uA.. f3.40 £3.60 50V AC .. £3 60
CtiviA f5 20 lmA 23.30 £3.60 150V AC.. C360 just ring 01-200 1321
10mA .. 25 20 5mA 23.30 (380
50rtiA 25.20 (3.60 300V AC ..
300V DC .. (5.20 10mA 23.30 £3 600 500V AC f 3 80
100mA f 5 20 50mA .. (3.30 10V DC .. 13.30 VU Meter.. .. 21 .10
500mA (5.20 15V AC .. (5.30 10OrnA (3.30 83.30
C3.6
lA AC EXPORT Personal exports
IA DC (5.20 300V AC (6.30 f3 60 .. f 3 60 arranged for overseas visitor,
s Meter lmA.. 14.20 500mA 23.30 (3 30 30A DC .. £3 60 5A AC .. (3 60
5A DC £5.20 IA DC 23.30 300V DC 23 .30 ISAAC .. £360 Goods specially packed,
15A DC £520 VU Meter (6.55 £3.80
£5.20 5A DC 13.30 15V AC .. (3 45 23.60 20A AC (3.60 insured and despatched to all
30A DC 25.40 IA AC ..
10A DC /3.30 300V AC .. (3.45 30A AC
lOy DC ISA AC .. .. £620 10V DC 23.80 13.60 parts OF the world at minimum
211.20
10A AC f5.20 5V DC (3.30 VU Mater.. (365 E3.60 50A AC (3.60 cost exclusive of VAT.
25.20 ..
500mA AC 13.60
25.20 20A AC .. .. 25.20 (3 60 ..
Payment by bank transfer.
150V DC .. 25.20 30A AC .. .. (5 20 POSTAGE & PACKING 15p (360 5051V DC .. (3 75
100rnV DC certified cheque. postal order

r-
1360 .. f 3 75
or money order in any
240° Wide Angle currency.
1
1mA METERS TO LASKYS CUSTOMER SERVICES DIVISION
m W1 -6 60 x 60 mm Audiotronic House. The Hyde. London NW9 6JJ. Te1.01 -200 1321
C6.50 P & P 15p BARCLAYCARD
MW1 4,80 80mm Please send me the following items & ACCESS
[6.90 P&P [-zit] Phony your
YAMABISHI VARIABLE ANL-
VOLTAGE TRANSFORMERS
Excellent quality et low cost. Input:
230V 50/80Hz. Output 0-260V.
FOR (ncelAP and VAT)
32 Page 11C
HI-FI
ME -RE
Ill® call into any branch
TOTAL PURCHASE PRICE
MODEL 5280 BENCH MOUNTING
1A £10.50
P&P
50p
MAIL I enclose cheque postal order money order
PRICE
LIST NO DEPOSIT TERMS
available on most goods
2.5A
5A
£12.00
E17.50
50p
50p ORDER I en. to pay by Barclaycard/Access for personal callers
BA £30.35 0.00 and my number ts
10A C33.75 21.00. We offer a speedy
12A 035.40 (1.11(1 and efficient MOUES to INC VALUE OF E38.
20A E85.00 E7.60 NAME ACCEPTED FROM PERSONAL SKIPPER!
25A £96.00 11 .60 service by mail O 111 OMER CASES
CARO.
40A £120.00 01.60 order. Remember ATON F011 01401111111 18 EXCESS OF DC
MODEL 5260B PANEL MOUNTING ADDRESS PLEASE ALLOW TINE fOR CLEARANCE.
2.5A 012.00 SOp to add 8% VAT MOIR* ODAFTS ACCEPTED.
to total value of
ALL PRICES goods including
Ali prices correct at 6/11/74 but
subject to change without notice E.&O.E.
EXCLUDE VAT Post and packing. Signature
neg,tered m England No 347941dt 12 LOwer Owenoc Place London SWI OE X PEI member of A.
AudlogrOAA Group of COMPORM

Practical Electronics 5
January 1975
 NOW AVAILABLE IN THE U.K!
CHINAGLIA
PROFESSIONAL QUALITY TEST EQUIPMENT FROM ONE OF ITALY'S LEADING MAKERS
One example from the big range of sophisticated Instruments

CORTINA MINOR .,
33 RANGE POCKET MULTIMETER AO V -se
noo
52
SENSITIVITY 20,0000/VOLT (D.C.), 4,0000/VOLT (A.C.). 50
ROBUST DIODE PROTECTED PRECISION MOVEMENT. 11K
33 RANGES D.C. VOLTS 0-100mV, I.5V, 5V, 15V, 50V, 150V,
500V, 1,500V. D.C. CURRENT 0-50µA, 5mA, 50mA, 500mA,
2.5A. A.C. VOLTS, 0.7.5V, 25V, 75V, 250V, 750V, 1,500V, 5
A.G. CURRENT 0-25mA, 250mA, 2.5A, 12 5A. dB RANGES, 5

-10 to +69. AF VOLTS RANGES 0-1,500V. RESISTANCE

RANGES 10k0, IOMO F.S.D. CAPACITANCE RANGES
IOW, IF F.S.D.
5 I 50
25
ACCURACY-RESISTANCE, D.C. VOLTAGE AND
CURRENT, 2.5%. A.G. VOLTAGE AND CURRENT 3.5%. so \\ 506 mA
RESISTANCE RANGES POWERED BY INTERNAL
BATTERIES. MINOR (army '

COMPACT SIZE : 150 x 85 x 40mm. 350gr.

CLEARLY CALIBRATED DIAL WITH ANTI -PARALLAX
MIRROR.
PROFESSIONAL QUALITY COMPONENTS EMPLOYED
-Q 1111
THROUGHOUT.
Chinaglia
BILL.. cam.
FULLY GUARANTEED FOR 12 MONTHS.
AFTER SALES SERVICE AND SPARES FACILITIES.
-+ .1.56 .1.561
SUPPLIED WITH ADDITIONAL SHOCKPROOF PLASTICS
CARRYING CASE, TWO HIGHLY INSULATED TEST
LEADS AND INSTRUCTION BOOKLET.
00 0
SPECIAL 30kV PROBE FOR D.C. MEASUREMENT AVAIL-
ABLE AS AN OPTIONAL EXTRA.

METER PRICE LI5.40 (p & p 80p) PROBE £8.80 inclusive of V.A.T.

for further information on the "Cortina Minor" or other instruments from the exciting Chinaglia range write or telephone :-

CHINAGLIA (U.K.) LIMITED

19 Mulberry Walk, London S.W.3. Telephone 01-352 1897
TRADE ENQUIRIES WELCOMED

--
I -N -T -E -R -L -0 -C -K -1 -N -G We make transformer,
OSMABET LTD. amongst other thing,.
I PLASTIC STORAGE DRAWERS AUTO TRANSFORMERS. 110/200/220/240V.

#010).vf ---.-.'-'-'
'----
mi.... j
--r-----9-r%
0
30W, £1.70; 50W. £2.40; 75W. £2.85: 100W, 13.80;
300W. 6111.80; 730W.114.25; 1000W, 11640, etc. TELEVISION
LOW VOLTAGE TRANSFORMERS
ilArie .11116i11111 Prim. 200/240V a.c. 6.3V 1.3A, 1140; 3A, 11.50;
1.1 '"-- _/
0°

0
6A, £2.55; 12V 1.3A, 11.80; 3A, 1245; 6A CT, 4,840.
18V 1-5A CT, £2.55: 24V 1 -IA CT, 42.55; 3A CT. CAMERA

14
DISCOUNT 1346; 50., 14410: 8A, /745; 12A, £10.86: 40V 3A

PRICES
----41-P1 0 0
CT, £4.60; 50V SA CT, 113.60; 23V 2A +25V 2A,
£4.90; 12V 4A +12V 4A. £4.90. KITS
LT TRANSFORMERS TAPPED SEC. Prim. 200/240Y
0 10 12 14 16 18V 2A, 12.80; 4.0. 13.70
0 12 13 20 24 30V 2A. 1340; 4A, £4.50:
0-5-00-30-40-60V Lk, 1.9.40; 2A, 1440;
Complete kits are available for
Newest, neatest I s saes 0-40-50-60-80-90-100-110V IA, 44.90. both "Mullard" and "P.E." design.
system ever All INTERIMS( MIDGET RECTIFIER TRANSFORMERS.
devised for storing small For FW rect. 200/240V a.c. 9-0-9V 0.3A: 12-0-12V Each kit includes a comprehensive
parts and components, 0.25A; 20-0-20V 0.15A, 6V 0.5A + 6V 0.5A; 9V construction manual, and a corn-
0.35A + 9N' 0.35A; 12V 0.23A + 12V 0.23A or
resistors, capacitors, diodes, transistors,
etc. Rigid plastic units interlock together
20V 0.15A + 12V 0.15A at 11.66 each; 9-0-9V IA, pletely FREE technical back-up
£156; 12-0-12V IA or 20-0-20N' 0.75A 11.60 each. service to ensure your success.
in vertical and horizontal combinations. MAINS TRANSFORMERS
Transparent plastic drawers have label slots. Prim. 200/240V a.c. TX6 sec., 425-0-425 300 Ma,
ID and 2D have space dividers. Build up any 6.3V CT 6A, 63V CT 6A, 0-5-6.3V 3A, 11640; VHF and UHF Modulator Kits
size cabinet for wall, bench or table top. TX1 425-0-423V 250 Ma, 6.3V CT 4A, 6.3V CT 4A, alsoavailable to allow standard
0-5-6.3V 3A, £9.75; MT3 Prim. 0-110-240V sec.

BUY AT TRADE PRICES! 250V 100 Ma, 6.3V 2A, E/S, 1240. domestic T.V. to be used as
SINGLE UNITS (ID) (Sins 2tins
0/P TRANSFORMERS FOR POWER AMPLIFIERS
P.P. sec, tapped 3-8-15ohms. A -A 6.6K (1 30W, monitor.
16.70; A -A 3K (I 50W, MOO; 100W (EL34 KISS.
-

2.lins). L2 DOZEN. etc.), £15.70; tapped Multi 0/P IOW £3. All parts available separately, in-
DOUBLE UNITS (2D) (Sins 4.1ins G.E.C. MANUAL OF POWER AMPLIFIERS
Covering valve amplifiers of 30W to 400W 85p. cluding a wide range of lenses,
2f ins). E3.50 DOZEN. LOUDSPEAKERS FOR AMPLIFIERS
BAKER 23W, £7.80; 35NV, 1840; HI -F1 Major vidicon tubes, special mains trans -
TREBLE (3D) £3.50 for 8. Module 20W w/tweeter Xover, 111430; Baker speaker 11 formers and focus/scan coils, also
DOUBLE TREBLE 2 drawers, in one outer lists; FANE; 50W, 41010; 60W, 41840; HI-FI available P.W. tele-tennis game.
case (6D2), 141.90 for 8. speakers, EMI bass 13 x 8in, MOO; Sin 80, 1145;
7 x4in 130, /1410; 8 x 5in 3, 8, 15, 23 or 800,
EXTRA LARGE SIZE (6DI) E4.50 for 8. 11.75 each. Send 5" x 7" S.A.E. for full details
LOUDSPEAKERS
PLUS QUANTITY DISCOUNTS! Ilin 8, 16 or 730, 21in 8 or 250, Sin 3, 8, 23 or or come along for a demonstration
Orders LIS and over DEDUCT in the C 350, 31in 8, 13 or 80(I OOp each: Sin 3, 8 or 230. and a chat with our technical staff.
Orders L30 and over DEDUCT 7i% in the d x 3in 3 or SO, 11.05: 7 x 4in 3 or 150, 611n 3(I,
1145; 10 x bin 3(1, 11.50.
PACKING/POSTAGE/CARRIAGE: Add 40p SPEAKER MATCHING TRANSFORMERS
to all orders under LIO. Orders LI 0 and over, 12W 3 to 8 or 130 op or down 4140.
packing/postage/carriage free.
"INSTANT" HULK TAPE/CASSETTE ERASER CROFTON ELECTRONICS
Instant erasure, any diameter tape spools, caasette,
QUOTATIONS FOR LARGER QUANTITIES demagnetises tape heads. 200/240V a.c. MU. MI 124 Colne Road, Twickenham
SYNCHRONOUS GEARED MOTORS, 880/240V. Middlesex TW2 6QS
Please add II% V.A.T. to total remittance Brand new, Smiths. Built-in gear box, 2 RP}I.
76p each. Telephone 01-898 1569
11..A1IXOGE (Dept. PE I ), 124 Cricklewood Carriage and VAT extra on all orders. Telex 934642 Cadanac LDN
(Broadway, London, N.W.2 S.A.E. ENQUIRIES -LISTS, MAIL ORDER ONLY
111
Tel. 01-450 4844
48 Kenilworth Road, Edgware, Middx. HAS BYG
Tel. 01-938 9:114

6 Practical Electronics January 1975

 SPECIAL BARGAIN OFFER!
SUPERSOUND 13 HI-FI MONO HARVERSONIC MAINS OPERATED Limited number of BSA C129 Auto Changer De Luxe
AMPLIFIER A superb solid state audio SOLID STATE STEREO FM TUNER with lightweight tubular arm and stereo cartridge.
amplifier. Brand new Brand new. ORLY 117.88 + p. & p. 60p.
components throughout.
3 Silicon translators
plus 2 power out -put HARVERSONIC SUPER SOUND
transistorsin push-pull.
rectifica-
10 + 10 STEREO AMPLIFIER KIT
Full wave
tion. Output approx.
13 watts r.m.s. into
8 ohms. Frequency
response 12Hz. 30KHz
3d1). Fully integrated
pre -amplifier stage with
separate Volume, Base boost and Enjoy Fabulous Stereo Radio at
Treble cut controls. Suitable for 8-15 ohm speakers.
Input for ceramic or crystal cartridge. Sensitivity
approx. 40mV for full output. Supplied ready built and
this Low Introductory Price!
tested, with knobs, escutcheon panel, input and output Designed and styiedto match our 10 + 10 amplifier
plugs. Overall size 3' high X 6' wide x 75' deep. but will suit any other standard stereo amplifier.
AC 200/250V. PRICE 411-80. P. & P. 50p. The design incorporates the very latest circuitry
techniques with high -grain, low noise IF stages. A really first-class Stereo Amplifier Kit. Uses 14
Automatic frequency control to "lock on" station and transistors Including Silicon Transistors in the first five
DE LUXE STEREO AMPLIFIER prevent drift. IC stereo decoder for maximum stereo stages on each channel resulting In even lower noise
A.C. main. separation. I.E.D. for stereo beacon indicator. Nom- level with improved sensitivity. Integrated pre -amp with.
200-240 v.
Using
heavy duty
inal output of tuner 100mV. Approximate size 121in wide
x 8in deep by 21in high. Supplied ready built, fully
Bass, Treble and two Volume Controls. Suitable for use
with Ceramic or Crystal cartridges. Very simple to
tested and fully guaranteed (not available In kit form). modify to suit magnetic cartridge -instructions included.
fully isola- Output stage for any speakers from 8 to 13 ohms. Compact
ted mains Price E2160. Post and Packing 50p. design, all parts supplied including drilled metal work,
transform - STEREO -DECODER SIZE 2" x 3" x i" high quality ready drilled printed circuit board with
er with full component identification clearly marked, smart brushed
wave recti- Ready built. Pre -aligned and tested. anodised aluminium front panel with matching knobs,
fication Sens. 20-560mV for 9-16V neg.
earth operation. Can be fitted to wire, solder, nuts, bolts -no extras to buy. Simple step
giving ade-
quate
smoothing with negligible hum.
almost any FM VHF radio or tuner.
Stereo beacon light can be fitted if
by step instructions enable any constructor to build an
amplifier to be proud of. Brief specifications: Power
Valve line -up: -2 It ECL86 Triode Pentodes. 1 x EZ80 required. Full details and in- output: 14 watts r.m.s. per channel into 5 ohms. Fre-
as rectifier. Two dual potentiometers are provided for structions (inclusive of hints and tips) quency response ± 3dB 12-30,000 Hz Sensitivity: better
bass and treble control, giving bass and treble boost and supplied. 16 plus 10p P. & P. than SOmV intb 1M O. Full power bandwidth: ± 3dB
cut. A dual volume control is used. Balance of the left and Stereo beacon light if required 40p 12-15,000 Hz. Bass, boost approx. to ± 12dB. Treble
right hand channels can be adjusted by means of a sepa- extra. cut, approx. to -16dB. Negative feedback 18dB over
rate 'Balance' control fitted at the rear of the chassis. main amp. Power requirements 35v. at 1.0 amp.
PRECISION ENGINEERED PLINTHS Overall Size 12'w. x frd. x 21'h.
Input sensitivity is approximately 300m/v for full peak Beautifully constructed In heavy gauge "Colorcoat' Fully detailed 7 page construction manual and parts
output of 4 watts per channel (8 watts mono), Into 3 ohm plastic coated steel. Resonance free. Designed to takelist tree with kit or send 18p plus large S.A.E.
speakers. Full negative feedback in a carefully calculated Garrard 1025, 2000, 2025TC, 2500, 6000, 2500, 5100, AMPLIFIER KIT .. 611.34 P. & P. 30p
circuit, allows high volume levels to be used with negligible SP25 II and III, 81.65B, AT60 etc. for B.S.R. C109, (Magnetic input components 33p extra)
distortion. Supplied complete with knobs, chassis size C120, A21 etc. Black leatherette finish. Sire 121' x POWER PACK KIT .. 13-46 P. & P. 40p
11'w x 4'd. Overall height Including valves 5'. Ready 145' x 35^ high (approx. 71 high, including rigid CABINET .. 113.46 P. & P. 40p
built and tested to a high standard. 610.22. P. & P. 50p. smoked acrylic cover). NOW ONLY 14-76. P. & P. 70p.
.

(Post Free if all unite purchased at same time)

POWER SUPPLY UNIT 200/240v. A.C. input. Four LATEST ACOS GP91/11C mono compatible cartridge with Full after sales service
switched fully smoothed D.C. output. giving 6v. and t/o stylus for LP/EP/78. Universal mounting bracket./ Also available ready built and tested 124.60. Post Free.
71v. and 9v. and 12v. at I amp on lead. 11.46. P. & P. 15p. Note: The above amplifier is suitable for feeding two mono
Fitted Insulated output terminals and pilot lamp indicator. SONOTONE °TAM COMPATIBLE STEREO CARTRIDGE sources into inputs (e.g. mike, radio, twin record decks, etc.)
Hammer finish metal came overall else 6' X 31' x 21'. T/O stylus Diamond Stereo LP and Sapphire 78. and trill then provide mixing and fading facilities for med-
Suitable for Transistor Radios, Tape Recorders, Ampli- ONLY 12-27. P. & P. 10p. Also available filed with twin ium powered Ni-Fi Discotheque use, etc.
fiers etc. etc. Ready n r Diamond T/O stylus for Stereo LP. 12-713. P. & P. 15p.
built and tested. Price £4 P. P. LATEST RONETTE T/O STEREO/COMPATIBLE 3 -VALVE AUDIO
AMPLIFIER HA84 MK II.
CARTRIDGE for EP/LP/Stereo 78. 21.110. P. & P. 15p.
VYNAIR &RETIE& SPEAKERS & CABINET FABRICS LATEST RONETTE TIC MONO COMPATIBLE CART- Designed for Iii -F1 reproduc-
app. 54 in. wide. Our price 111.10 yd. length. P. & P. 16p RIDGE for playing EP/LP/78 mono or stereo records tion of records. A.C. Mains
per yd. (min. 1 yd.). S.A.E. for samples. on mono equipment. Only 21.47. P. & P. 15P operation. Ready built on
plated heavy gauge metal
HARVERSON'S SUPER MONO AMPLIFIER QUALITY RECORD PLAYER AMPLIFIER ME. chassis, size 71'sv. x 4'd. x
A super quality gram amplifier using a double wound fully A top quality record player amplifier employing heavy 41'h. Incorporates ECC83,
misted mains transf ormer, rectifier and ECL82 triode duty double wound mains transformer, ECC83, EL84, EL84, EZ80 valves. Heavy
and rectifier. Separate Bass, Treble and Volume controls. duty, double wound mains
pentode valve as audio amplifier and power output Complete with output transformer matched for 3 ohm
stage. Impedance 3 ohms. Output approx. 3.5 watts. transformer and output trans-
Volume and tone controls. Chaasis else only 71n. wide speaker. Size 7in wide x Sin deep x 6in high. Ready former matched for 3 ohm
x 3M. deep x Sim high overall. AC mains 200/240v. built and tested. PRICE 14.61. P. a P. 50p. speaker. Separate volume control and now with improved
Supplied absolutely Brand New completely wired and ALSO AVAILABLE mounted on board with output wide range tone controls giving bass and treble lift and
transformer and speaker. PRICE 4610. P. & P. 60p. cut. Negative feedback line. Output 41 watts. Front
tested with gooP. d qua transRICE .
outputAIN
P. & 4 0p. BlityARG P a..78
Lformer
panel can be detached and leads extended for remote
HI-FI LOUDSPEAKER SYSTEMS mounting of controls. Complete with knobs, valves, etc.,
BRAND NEW MULTI -RATIO MAINS TRANSFOR- wired and tested for only 1640. P. & P. 45p.
MERS. Giving 13 alternatives. Primary: 0-210-240.. Beautifully made teak finish enclosure with most ESL "FOUR" AMPLIFIER KIT. Similar In appearance
Secondary combinations 0-5-10-15-20-25-30-35-40-60s attractive Tygan-Vynair front. Sloe 18' high x 105' to HA34 above but employs entirely different and
half wave at I amp. or 10-0-10, 20-0-20, 30-0-30v. at wide X 6'deep. Fitted with E.M.I. Ceramic Magnet advanced circuitry. Complete set of parts, etc. 14-92.
2 amps fulls wave. Size Sin. long x 31In. wide x 3M. 13- x 8' bass unit, two H.F. tweeter units and P. a P. 45p.
deep. Price 12-31. P. a P. 40p. crossover. Maximum power handling 10 watts.
MAINS TRANSFORMER. For translator power supplies. Available 3 or 8 or 15 ohms impedance. 10/14 WATT
Pro. 200/240v. Sec. 9-0-9 at 500 mA. 81-10. P. & P. 25p. Carr. 75p. AMPLIFIER KIT
Pd. 200/240v. Sec. 12-0-12 at 1 amp. 41.21. P. a P. 26p OUR PRICE £9.10. Carr. 75p. A stylishly finished
monaural amplifier
Prl. 200/240v. Sec. 10-0-10 at 2 amp. 11.82. P. a P. 35p. Cabinet Available Separately 14-136. Carr. 65p.
Also available in 8 ohms with EMI 13' X V bass with an output of
HI -GRADE COPPER LAMINATE BOARDS speaker with parasitic tweeter 27.60. Carr. 75p. 14 watts from 2
V X 6'. Five for 60p plus 90p P. a P. EL8411 In push-pull.
LOUDSPEAKER BARGAINS Super reproduction
GENERAL PURPOSE HIGH STABILITY Sin. 3 ohm 81-89, P. & P. 15p. 7 x 4in. 3 ohm 11-40, P. a P of both music and
20p. 10 x Sin. 3 or 15 ohm 12.10, P. a P. 30p. E.M.I speech, with negli-
TRANSISTOR PRE -AMPLIFIER gible hum. Separate
For P.C. Tape, Mike, Guitar, etc. and suitable for 8 x Sin. 3 ohm with high flux magnet 21.70, P. & P. 20p inputs for mike and
use with valve or transistor equipment. 9-18v. E.M.I. 131 x 8in. with high flux ceramic magnet with gram allow records
battery or from H.T line 200/300v. Frequency parasitic tweeter 3, 8 or 15 ohm 1360, P. a P. 90p and announcements
response 15Hz-25KHz. Gain 26dB. Solid encap- E.M.I. 13 X 8in 3, 8 or 15 ohm with two inbuilt tweeter to follow each other.
sulation size It' x lt" x 5'. Brand new complete and crossover network 141.66, P. a P. 30p. Fully shrouded section wound output transformer to
with instructions. Price 98p. P. a P. 15p. E.M.I. tweeter. Approx. 35'. Available 3 or 8 or 15 ohms match 9-15 0 speaker and 2 Independent volume control.,
111.29 + 20p, P. & P. and separate base and treble controls are provided
HANDBOOK OF TRANSISTOR EQUIVS. AND SUBS.
BRAND NEW. Bakers Loudspeakers at substantial die giving good lift and cut. Valve line-up 2 EL84e, ECC83,
A must for servicemen and home constructors. Including counts. 121n. 15w. H/D Speakers, 3, 8 or 15 ohms EF86 and EZ80 rectifier. Simple instruction booklet
many 1000'e of British, U.S.A. European and Japanese State which. Current production by well-known British 15p X SAE (Free with parts). All parts sold separately.
transistors. ONLY 40p. Post 5p. maker. Now with Hiflux ceramic ferrobar magne ONLY 19.60. P. a P. 60p. Also available ready built and
assembly 1740. Guitar models: 25w. 27-60. 35w. 1.3.50
8 Reference Encyclopedias for Electronic ',newer' and P. a P. 45p. tested 112.75. P. & P. 70p.
Designers, covering between them transistor character- 12in. "RA" TWIN CONE LOUDSPEAKER. 10 watts
istic, diode and translator equivalents. Many thousands HI -F1 STEREO HEADPHONES
of up to date European types listed. peak handling. 3 or 8 or 15 oho: (state which) 12.70. Adjustable headband with comfortable &idiom ear-
Diode Equivalents 80p. Transistor Equivalents 90p. P. a P. 36p. muffs. Wired and fitted with standard stereo tin jack
Transistor Characteristics 11.19. POST FREE
"POLY PLANAR" WAFER -TYPE, WIDE RANGE plug. Frequency response 30-15,00014s. Matching
All three together 12-60. EXECTRO-DYNAMIC SPEAKER mpedance 8-16 ohm.. Easily converted for Mono.
Size 115' x 1411' x 1 ,f,." deep. Weight 19os. Power PRICE 1344. P. & P. 25p.
NEW ISSUE handling 20W r.m.s. (40W peak). Impedance 8 ohm only.
Thyristor, Trion, Diac etc. encyclopedias 96y. Poet Free. Response 40Hs-20kHs. Can be mounted on ceilings,
8 pole 3 way 2 bank low loss Yaxl y type switches If'
walla, doors, under tables, etc., and used with or without
baffle. Send S.A.E. for full details. Only 1643 each.
'PRICES INCLUDE VAT AT 8%
sections. Standard spindle. 2 switch a 64p + 10p P. & P. P. & P. 34p.
Open 9.30-5.30 Monday to
Friday. 9.30-5 Saturday HARVERSON SURPLUS CO. LTD. (Please write clearly)

Closed Wednesday. (Dept. P.E.) 170 HIGH ST., MERTON, LONDON, S.W.I9 Tel,: 01-540 3985 Ingt.,wil.lenspay
ORDERS
P. dr P. ON OVERS
A few minutes front South IV tinbl, CHARGED EXTRA.EAS
don Tube Station SEND STAMPED ADDRESSED ENVELOPE WITH ALL ENQUIRIES

7
Practical Electronics January 1975
 TRANSFORMERS NEW PE
SAFETY MAINS ISOLATING TRANSFORMERS SCORPIO
Prim. 120/240V. Sec 120/240V Centre Tapped and Screened
ALSO AVAILABLE WITH 115/120V SEC. WINDING
Ref. VA Weight Size cm. P& P
Mk. 2
No. (Watts) lb or p
07 20 I B 7.0 x 6.0 x 6.0 2.55 38
49 60 3 12 9.9 x 7.7 x 8.6 3.98 45
50 100 5 8 9.9x 8.90 8.6 4.45 45 Following the phenomenally successful Scorpio Capacitor -Discharge
51 200 8 0 2.1 x 9.3 x 10.2 7.39 53 Electronic Ignition system introduced in 1972 and proved by many
52 250 13 12 2.1 x 11.8 x 10.2 8.93 73 thousands of satisfied motorists, we are happy to announce avail-
53 350 15 0 4.0 010.8 x 11.8 10.80 73 ability of all parts for the PE SCORPIO Mk. 2-
54 500 19 8 4.0 013.4 x 11.8 12.41 91
55 750 29 0 7.2 x 14.0 x 14.0 18.65 Now with added R.F.I. suppression.
56 1000 38 0 7.2 016.6 x 14.0 26.50 Fully machined and painted die-cast case with AMP termination
57 1500 46 0 21.6013.4018.1 30-23 connector block.
38 2000 60 0 21.6015.3018.1 33.70 *Custom wound transformer.
AUTO TRANSFORMERS NOW AVAILABLE IN 6V. and 12V.
Ref. VA Weight Size or,,. Auto Tops P&P Suitable for all types of Cars, Boats, Go -Karts, etc.
No. (Watts) lb oz p
113 20 1 0. 5.8 x 5.1 x 4.5 0-115-210-240 1.52 30 Promotes easier starting -even under sub -zero conditions.
64 75 2 4 7.0 x 6.7 x 6.1 0-115-210-240 2.64 38 Improves acceleration, gives better high speed performance and
4 150 3 4 8.9 x 7.7 x 7.7 0-115-200-220-240 3.75 45 quicker eniine warm up.
66 300 6 4 9.9 x 9.6 x 8.6 5.29 53 Eliminates excessive contact breaker burning and pitting.
67 500 12 8 12.1 x 11.2 x 10-2 8.02 67 PROMOTES FUEL ECONOMY.
84 1000 19 8 14.0 x13.4 x14.3 12.44 91
93 1500 30 4 14.0 x 15.9 x 14.3 16.65 Construction of the unit can easily be completed in an evening -
95 2000 32 0 17.2 x 16.6 x 14.0 22.00 installation should take about half an hour. A complete complement
73 3000 40 0 21.6 x 13.4 x 18- I 31.90 of components is supplied with each kit Together with ready drilled,
CASED AUTO TRANSFORMERS roller tinned professional 'quality fibreglass printed circuit board.
115V mains lead input and U.S.A. 2 -pin outlets, 20VA £2.85. P & P 38p. -Uses original plugs, points and coil. -No special parts or extras
SOOVA L9-50. P & P 80p. I000VA [13.92, via B.R.S. required. (Case size: Thin x 41in x 2in)
LOW VOLTAGE SERIES (ISOLATED) All components available separately.-S.A.E. with enquiries.
PRIMARY 200-250 VOLTS 12 AND/OR 24 VOLT RANGE
Ref. Amps. Weight Size crn. Secondary Windings P&P Construction manual available separately 25p.
No. I 2V 24V lb or 1 p
III 0.5 0.25 8 4.8 x 2.9 x 3-5 0-I2V at 0.25A x 1 1.34 23 Cost 111-78 incl. carr. and ins. or ready built and tested 014.49
213 1.0 0.5 I 4 6.1 x 5.8 x 4.8 0-12V at 0.5A x2 1.58 30 Conversion kit from Mk. to Mk. 2. For constructors already
I
71 2 12 7.0 x 6.4 x 6.1 Q -12V at IA x 2 2.09 38
18 4 2
I
2 12
I
8.3 x 7.7 x 7.0 0-I2V at 2A x 2 2-60 38
possessing Mk. IKits. -Miniature P.C. assembly LI intl. carr. and
70 6 3 3 8 8.9 x 8.0 x 7-7 0-12V at 3A x 2 3-75 45 ins. With full conversion instructions.
108 8 4 5 8 9.9x 8.9x 8-60.12V at 4A x 2 4-15 45 PLEASE ADD VAT TO ALL U.K. ORDERS
72 10 5 6 4 9.9 x 9.6 x 8-6 0-12V at 5A x 2 4.67 53
116 12 6 6 12 9-9 010-2 x 8.6 0-12V at 5A x2 5.02 53 (Carriage at cost outside U.K. Export enquiries welcome.)
-

17 16 8 8 12 12.1 x 9.9 010.2 0-12V at 8A x 2 6-62 60

115 20 10 8 14-0 x 9.6 x 11.8 0-12V at 10A x 2 9.45 73

it
I I
187 30
226 60
15 15
30 32
8 14.0 x 12.1 x 11-8 0-12V at 15A x 2
17.2x 15.3x 14.0 0.12V at 30A x 2
12.29 85 DABAR ELECTRONIC PRODUCTS
Ref. Amps Weight
0

Size cm.
30 VOLT RANGE
Secondary Taps
15.30
P&P
98 LICHFIELD STREET rimje
No.
112 0.5
lb oz
I 4 6-I x 5.8 x 4.8 0-12-15-20.24-30V
C
1.65
p
30
WALSALL, Staffs WSI I UZ 6,42t4
79 1.0 2 4 7.0 x 6.7 x 6.1 2.10 38
3 2.0 3 4 8.9 x 7.7 x 7.7 3.18 38
20 3.0 4 8 9.9 x 8.3 x 8.6 4.12 45
21 4.0 6 4 9.9 x 9.6 x 8.6 4.67 53
51 5.0 6 12 12.1 x 8.6 x 10.2 5.83 53
117 6.0 8 0 12-1 x 9.3 010.2 6.51 60
88 8.0 12 0 12.1 011.8 x10-2 9.00 67
89 10.0 13 12 14.0 010-2 0 11-8 8.97 73
50 VOLT RANGE
Ref. Amps. Weight Size cm. Secondary Taps P&P
No. lb oz C p
02 0.5 I 12 7.0 x 6.4 x 6.1 0-19.25-33-40-50V 2.35 30
03 1.0 2 12 8.3 x 7.4 x 7-0 3.08 38
04 2.0 5 8
05 3.0 6 12 9.9 x 10.2 0 8-6 ',, 5.28 53
06 4.0 10 0 12.1 x 10.5 x10.2 6.91 67
07 6-0 12 0 14.0 010.2 011.8 11.00 67
18 8.0 18 0 14.0 x 12.7 011.8 11.80 85
19 10.0 25 0 17.2 012.7 014 0 1545 '
60 VOLT RANGE
Ref. Amps. Weight Size cm. Secondary Taps P&P
No. lb az C p
124 0.5 2 4 7-0 x 6.7 0 6.1 0.244040-48-60V 2.12 38
126 1.0 3 4 8.90 7.7x 7.7 .. ,, 3.10 38
127 2.0 6 4 9.9 x 9.6 x 86 ,, 4.62 45
125 3.0 8 12 2.1 x 9.9 x10.2 6.84 60
123
40
120
121
4.0
5.0
6.0
8.0
13

15
12
12 00
8
25 00
2.1 011.8 x10.2
4 0 010-2 011.8
4.0 012.1 011.8
4 0 x14-7 x 11.8
,,
7.96
8.87
10.27
13.64
67
73
85 1140
122 10.0 25 0 7.2 012.7 014 0 15.93
189 12.0 29 00 7.2 014.0 014.0
..:
18.16 Go°
MINIATURE TRANSFORMERS WITH SCREENS
Ref.
No.
238
212
mA

200
IA, IA
Weight
lb
I
oz
2
4
Size cm.
2.8 x2.6 02.0
6.1 x5.8 x4.8
3-0-3
0-6, 0.6
Volts
L
1.40
1.67
P&P

30
p
10 become
13 100 4 3.9 x2.6 x2.9 9-0-9 1.28 13
235
207
208
236
330, 330
500, 500
IA, IA
200,200
100
1
4

12
4
48 x 2.9 x 3.5
6.1 x 5-4 x 4.8
7.006.406.1
4.8 x 2.9 x3.5
0-9, 0-9
0-8-9, 0-8-9
0.8.9, 0-8-9
0-15, 0-15
1.42
1.75

1.30
19
30
3.00 38
19
a RADIO -AMATEUR!
214
221
300, 300
700 (d.c.)
I

I
4
8
6.1 x 5.8 x 4-8
7.0 -< 6.1 x 6.1
0-20, 0-20
20-12-0-12-20
1.76 30
1.98 38
learn how to become a radio -amateur
206 IA, IA 2 12 8.307-7 x7.0 0-15-20, 0-15-20 3.15 38 in contact with the whole world. We give
203 500,500 2 4 8.3 x7.0 x7.0 0-15-27, 0-15-27 2.73 38
skilled preparation for the G.P.O. licence
204 IA, IA 3 4 89,-7707.7 0-15-27, 0-15-27 3.50 38
*Carriage via B.R.S.
PLEASE ADD 8% FOR V.A.T.
INCLUDING P. & P.
free ! Brochure, without obligation to:

BARRIE electronics BRITISH NATIONAL RADIO & ELECTRONICS SCHOOL

Dept. EB124, P.O. BOX 156, JERSEY
3,THE MINORIES, LONDON EC3N 1BJ NAME:
EB15
TELEPHONE: 01-488 3316/8 ADDRESS:
NEAREST TUBE STATIONS ALDGATE & ALDGATE EAST BLOCK CAPS please

8 Practical Electronics January 1975

 TRANSISTORS, VALVES AND SEMI- EREE NEW
SE 74
CONDUCTOR DEVICES ANY QUANTITIES
UK'S LARGEST STOCKISTS AND/75
neciDUCT"
0rM i-
Ref NI/0A. I -3116E LISTS
INTEGRATED COSMOS INTEGRATED
CIRCUITS CIRCUITS. FULL
74 SERIES & LINEAR RANGE IN STOCK TEST
EXTRA DISCOUNTS AA213
p
0.12 BLY36
BSX20
p
6.00
0.13
TIP42A
TIS43
p
0-90
0.28
EQUIPMENT
AC107 0.51
Semiconductors -Any one type or mixed AC128 0.15 BU105 2.20 V405A 0.22
SN74 Series IC 12 -extra 10%; 25 -extra
15%, 100 -extra 20%.
AC187
ACY17
ACY39
0.21
0.40
BY100
BY127
BYZ13
0.27
0.12
0.42
ZTX108
ZTX300
ZTX302
0.08
0.13
0.18
MULTI- 1\

SN740074
p
0.16 SN7485N
t
1.63
p
SN74191N
p
2.00
AD149
AD1131
0.78
0.50
0.44
C1060
GET111
0.54
0.72
ZTX500
25697
2N 706
0-13
0.16
0.12
METERS
A13162 0.44 GET115 0.90
SN7401N 0.16 SN7486N 0.47 SN74192N 2.00
0.24 GET880 0.60 25930 0.18 Karr.
AF117 IVIih cue O
SN7402N 0.16 SN7489N 3.87 SN74193N 2.00 LM309K 2.00 25987 0.42 tA1Y21
AF118 0.57
SN7403N 0.16 SN7490N 0.70 SN74194N 1.30 MAT121 0.25 2N1132 0.24 0435 20kr11V w.th steel
AF139 0.41
SN 4045 0.16 SN7491AN 1.00 SN74195N 1,10
AF186 048 MJE340 0.47 251304 0.28 cue 8.75
SN 405N 0.16 SN7492N 0.70 SN74196N 1.20 2N1613 U4313 2061115 with etee1
AF239 0.44 MJE520 0.63 0.21 1250
SN 406N 0.42 SN7493N 0.70 SN74197N 1.20 MJE3055 0.77 261671 1.20
C2110
ASY27 0.33 U4317 201/ V with case 9850
SN 407N 0.42 SN7494N 0.80 SN74198N 2.77 MJE2955 1.27 2N2147 0.78
BA115 0.10 04341 331711/ plus transistor steel
SN 408N 0.21 SN7495N 0.90 SN74199N 2.52
MPF105 0.36 262160 0.78 10,50
BAX13 0.05 Ca.
SN7409N 0.28 SN7496N 0.95
BC107 0.14 NKT404 0.66 2N2926 012 U4323 20kfIN plus NH: OSC case
with 7,70
SN7410N 0.16 SN7497N 317 0A5 0.72 253053 0.18 ITI-2 2okilv slim type 5-65
BC108 0.13 7.50
SN 411N 0.25 SN74100N 1.89 RCA BC109 0.14 0A81 0-18 2N3054 0.48 THL33D (1.33D X) 2171.V Robust
SN 412N SN74104N CA3012 0-45 TP5SN 2063 V (Cass 8-25
0.30 0.58 1.32
BC109C 0.16 0A200 0.06 253055 721
6.25
SN 413N 0.36 SN74105N 0.53 CA3014 1.80
BC113 0.15 0A202 0.04 2N3440 0.58 11,100 2k NV
10-00
SN 414N 0.72 SN74107N 0.45 CA3018 1.02 263442 1,-39 TW20S 20671,V
BC147 0.10 0C28 0.66
TW50K 50k71/V 11-25
SN 416N 0.36 SN74110N 0.58 CA3019 1.12
0C35 0.55 2N 3525 0.91 8-05
SN74111N
BC148 0.08 EP1OKN 10k71/V
SN 417N 0.36 0.69 CA3020 1.80
BC149 0.10 0C36 0.60 263614 0-65 AF105 50k3/V Deluxe (case (1 B01 12-50
SN 420N 0.16 SN74116N 1.68 CA3022 1 93
BC169C 0.15 0C44 0.20 2N3702 0.11 S100TR tookn,v plus transistor tester 2250
SN 421N 0.33 SN7411136 0.90 CA3028A 1.03 0C45 0.20 263714 1.41
SN 422N 0.25 SN74119N CA3036 1.08 BC162 0.12
253771 1.77
1.68
BCY32 0.85 0071 0.18
SN 423N 0.37 51,174120N 0.95 CA3046 1.03
BCT39 1.50 0072 0.28 253773 2-40
SN 425N SN74121N 2N3790
SN7426N
0.37
0.32 SN74122N
0.50
0.70
CA3048
CA3075
2.76
1.75
BCY55 2.64 0077
0081
0-54
0.29 253819
2.10
0.38 GENERAL TEST EQUIPMENT
BCY70 0.18
SN 427N 0.37 SN74123N 1.00 CA3081 1.80
BCY71 0.22 0083 0.27 263886 0.72 - Carr, packing 50p Carr
SN 428N 0.40 SN74125N 045 CA3089E 2.94 0C140 1.14 253903 0.15 packing 30p) unless embed
BCY72 0.12
SN 430N 0.16 SN74132N 0.72 CA30900 5.40
B0124 0.65 0C170 0.30 264002 0.14
SN7432N 0.37 SN74141N 0.00 Signetks BD131 0.42 0C200 0.54 2N4126 0-15 NEW
SN7433N 0.37 SN74145N 1-215 NE555 0.85 0C202 264871 0.34
0.37 NE560B
BF115 0.20 0.90 REVOLUTIONARY
SN7437N SN74150N 1.75 5,00
OCP71 1.20 265457 0.30
SN7438N 0.37 SN74151N 1.00 NE561B 5.00
13E180 0.36
25303 0.60 SUPERTESTER
BF194 0.10 ORP12 0.60
6608 p
SN7440N 0.22 SN74153N 0.95 NE562B 5.00
OR P60 0.55 40550 0.54 C
BFX13 0.26
SN7441AN 0.92 SN74154N 2.00 NE567B 3.5
BFX34 0.70 P346A 0.16 40361 0.45 6808 Multi -tester 18.50
SN7442N 0.79 SN74155N 1.00 Motorola TIL209 0.20 40362 0.40
SN7443N 1.27 5674156N MC1303L
BFX88 0.24
1.00 1.42
B FY50 0.21 TIP29A 0.45 40408 0-50 Acceseories
SN7444N 1.27 Sh174157N 0.95 MC1304P 1.7
TIP30A 0.57 40486 0-85 Transistor tester 11.00
1.60 EIFY51 0.20 1I 00
SN7445N SN74160N 1,38 MC1310P 2.81
TIP31A 0.61 40636 1.00 Electronic voltmeter
1.89 B FY64 0.36 11:t
SN7446N SN74161N 1.38 MC1458CF 0.77 TIP41A 0.74 40430 0.85 Ampclamp
1.60 B FY90 0.31 11,95
SN7447AN SN74162N 1.38 MC1710CC 0.80 Temperature probe
SN 448N 1.27 SN74163N 1.38 MFC4000P 0.45 Gauss meter 11.05
SN 450N 0,16 SN74164N 1.78 MFC4010P 0.55 Signet injector 545
SN 451N
SN7453N
0.16
0.115
SN74165N
5674166N
1-76
1.60
MFC6040P
Others
1.00
SILICON TRIACS Ph... sequence
ENT probe
5.95
5.05
p
SN7454N
SN 460N
0-16
0.16
SN74167N
SN74170N
3-00
2.52
TBA000
SN76003N
1.50
1.50
CONTROLLED SC35A 0.85 Shunts 25150-100A
r 3100 IMA Strip chart recorder
1.54
41.0$
SN 470N
SN 472N
0.38
0.38
SN74173N
SN74174N
1.68
1.57
SN72741P
SN72748P
0.150
0.81
RECTIFIERS SC35B
SC350
0.91
0.99
7140 AC Multivoltrneter
7615 Grid dip meter 440101,28mHz
10,75
10.50
SN7473N 0.41 SN74115N 1.10 702C 0.75 SC35E 1.30 -Tk85 28 Mingo valve voltmeter 22,50
SN7474N 0.42 SN74176N 1.26 709C 0.39 TO5 1 Amp E p 8 Amp Tk201) RF Generator 120k118-500mhly 1815
SN7475N 0.59 SN74177N 1.20 723C 0.90 CRS1 05AF 0.42 SC4OA 0.88 -76220 AF Generator 206M-200kHz 10-03
SN7476N 0.45 SN74180N 1.28 728C 0.45 CRS1 10AF 0.48 SC4OB 0.97 HM350 in circuit transistor tester 111-50
SN 4806 0.60 SN74181N 3.95 741C 0.50 CRS1,20AF 0.52 SC40D 1.20 0,05
C3025 Deluxe meter 1-300,1111y
SN 481N 1.10 SN74182N 1.26 747C 1.00 CRS,40AF 0.80 SC40E 1.50 77145 Compact transistor tester '4,75
SN 482N 0.07 SN74184N 1.80 748C 0.81 CRS1,60AF 0.78 10 Amp
SN7483N 1.10 SN74185N 1.80 LM309K 2.00 T040 3 Amp SC45A 1.09
SN7484N 1.00 SN74190N 2.00 TAA960 1.75 CRS3,025AF 0.315 SC45B 1.12
CRS3/10AF 0'44 SC45D 1 -SO
PA -DISCO LIGHTING EQUIPMENT
CRS3,(20AF 0.54 SC45E 1.85
CRS3/40AF 0.85 15 Amp
ELECTRONIC COMPONENTS CRS3/60AF 0.80 SC50A 1.46
(Poet/Packing 15p per 1-4 Items G.B. unto. stated) TO48 7 Amp SC5OB 1.57
CRS7'400 0.84 SC500 1.80
Ultrasonic transducers CRS7 600 1.14 SC50E 2.00
With date circuits E5-90 TO413 16 Amp Also
pair CRS16.100 0.78 40430 0.85
Strobe lobes CRS16/200 0.85 40669 0.90
ZFT8A (similar to 4A) (4. CR016/400 0-96 40486 0.85
Ceramic Filters ZFT12A E5. Without doubt U K.'s best range of modular and
Miniature 10 7 mHz filters 7 segment Indicators complete equipment. Lighting. mixing, micro-
46p pair 3015F with data E1,70 each phones. accessories. speakers. amplifiers.
IC IF Unit Spring dally unite lenses, etc.. etc.
CA3089 10,7 mHz HP42 Oin twin spring 0230 BRIDGE SILICON FREE stock lists (Ref. No 18) on request. CALL
IC E2-94 (P 8 P.1 20p HR1 Oin twin
IC Clock bi
spring E8.115 (P 8 P.) 25p RECTIFIERS IN AND SEE FOR YOURSELF at HENRY'S DISCO
MM 5314 single Fibre optics CENTRE, 309 EDGWARE ROAD. TEL. 01-7236963
chip Clock with I
0.01in die mono filament
CCT Ell. A e, E5.50 per 100 metres 0.13in Amp p p
Radio IC Chip
ZN414 Radio IC
die 64 fibres t1 per metre
15mm dia. mares tails B025/025 0.14 B2 20 0.40 6 Amp
0.50
kgrloYZNIaliaLK.24-1=1111=
B025/05 0.16 B2,40 0/44 8600
with ctrcuitt1.29. t10 SO each.
0.45 136/10
0.58 Living Sound made specially for
1 Amp 82/60 0.68 Henry's by EMP Tapes Ltd. 5 screw
B1/05 0.20 82,100 0.55 136/20
TAPE HEADS 86 40 0./5 type with library case. Post paid (11.8.).
B1/10 0.21 4 Amp
MARRIOT XRPS 17 i Track High (2.50; XRPS118 i Track Med BI '20 0.24 84/05 0.45 B6/60 0.07
£3.50; XRPS.36 i Track Med. MOO; XRPS/33 f Track High 94/10 0.48 1 Amp Tubular
E1.75; Erase Heade for XRPS/17/18136 (XES11) ?Sp; 13X12E 343 81,60 0.25 3 for 6 fo 10 for 25 for
Tr. Erase 75p. 81/100 0.30 84/20 0.54 W005 0 27
0.60 WO1 0.29 COO 110 2.00 3 15 7 50
RiRIN Record/Play I Track 45p. 2 Amp 84/40
H,RP Single Track Rec./Play 35p. 0.70 W02 0.30 C90 1-47 2.85 4.85 11,37
B2/05 0.30 B4/60
Bogen Type UL290 Erase t1.60. B2 10 0.35 84/80 0.90 W06 0.33 C120 1-83 3.54 5.60 14-00
Miniature Stereo Cassette Rec./Play 12.25.
Electronic Centres

Henry's EDGWARE ROAD, W2

RADIO
404-406 Electronic Components & Equipment 01 -4028381 Hi Fi and
309 PA -Disco -Lighting High Power Sound 01 -723 6963
303 Special offers and bargains store
All mail to 303 Edgware Road. London W2 18W
.
Electronics
Centres Open
9 am - 6 pm
Prices correct at time of preparation. Subject to change without notice. E.&0 E.

9
Practical Electronics January 1975
 The largest selection
EX COMPUTER BOARDS IT'S NEW
Packed with transistors, diodes, capacitor.
and resistors -COMPONENT VALUE 11.50.
BIB HI-FI ACCESSORIES
3 for ONLY 56p + P. & P. 30p. De Luxe Groov-Kleen IT'S POWERFUL
SPECIAL one as above PLUS Power Tran
sisters ONLY 55p each + P. & P. 15p. Model 42 E1 95 (15+ 1 5w R. M.S.) AND -
PAXOLINE BOARDS 71 x 9" approx. Chrome Finish
4 for 90p + P. di P. 20p.
Model GO £1. 50
IT LOOKS GOOD!
FIBRE -GLASS PRINTED THE
Ref. 36A. Record/Stylus Cleaning Kit 88P Rd. B. Stylus and Turntable Cleaning Kit
CIRCUIT BOARDS Ref. 43. Record Care Kit 18.42 Ret. P. HI-FI Cleaner 31p 849
LEGIONAIRE
161 x 4' approx. 2 for 55p Ref. 91. Cassette Head Cleaner 58p Ref. 32A. Stylus Balance 111.117
R f 32 Tape editing Kit 21.68 Ref. J. Tape Head Cleaning Kit 82p STEREO
Model 9. Wire Stripper/Cutter 83p Ref. 56. 111 -Fl Stereo Hints and Tips 42P
DECON-DALO 33PC Marker Ref. 46. Spirit Level 62p 1 Rd. 45. Auto Changer Groove Cleaner 11.08 AMPLIFIER
Etch resistant printed circuit marker pen
990 each ANTEX SOLDERING IRONS PLUGS AND SOCKETS ORDER NOW -
PLUGS
VEROBOARDS
X25. 25 watt 12.05
PS 1 D.I.N. 2 Pin (Speaker) 0-11
ONLY £39.95 p. & p. 50p
Packs containing approx., 50sti . in. various CCN 240. 15 watt 12.48 PS 2 D.I.N. 3 Pin 0.12 OR Write for full details
sizes, all 0.1 metric 55p Model O. 18 watt 12.26 PS 3 D.I.N. 4 Pin 0.15
0K2. Soldering Kit 18.25 PS 4 D.I.N. 5 Pin 180° 0.16
REPANCO CHOKES & COILS
RF Chokes
STANDS: 8T3, suitable for all models 111
SOLDER: 18SW0 Multicore 7oz 2141
PS 5
PS 6
D.I.N. 5 Pin 240°
D.I.N. 6 Pin
046
0.17
WORLD SCOOP
CHI. 2.5m1I 29p Cil2. 5.0n1H 30p
CH4. lOrnH 33P 22SWO 705 5141. 1138WO 22ft PS 7 D.I.N. 7 Pin 0-18 JUMBO
CH3. 7.5mH 3Ip P8 8 Jack 2.5mm Screened 0-18
CH5. 1.5n1I-1 289 22SWG Tube SOP
P8 9 Jack 3.5mm Plastic 0.12
SEMICONDUCTOR PACK
COILS
DRX I Crystal set 31p DR R2 Dual range 45p PS 10 Jack 3.5mm Screened 0.18 Transistors, Germ. and Silicon Rectifiers,
ANTEX BITS and ELEMENTS PS 11 Jack 1' Plastic 0.15 Diodes, Triacs, Thyristors, I.Cs and Zenere.
Bits No. PS 12 Jack 1' Screened 0.22 ALL NEW AND CODED.
COIL FORMERS & CORES
NORMAN r Corer A Formers 8p 102 For model CN240 e' 42P PS 13 Jack Stereo Screened 0.36 APPROX 100 PIECES
Cores A Formers 10p 104 For model CN240 420 PS 14 Phono 040 Offering the amateur a fantastic bargain Pak
PS 15 Car Aerial 0.22 and an enormous saving -identification and
1100 For model CCN240 42p
PS 16 Co -Axial 0.15 data sheet in every Pak.
SWITCHES 1101 For model CCN240 1' 92p
DP/DT Toggle 38p SP/ST Toggle 1109
1102 For model CCN240 1' 42p INLINE SOCKETS Only £2 p. & p. 20p
PS 21 D.I.N. 2 Pin (Speaker) 0.14
1020 For model 0240 is' 42p
FUSES PS 22 D.I.N. 3 Pin 0.20
II' and 20mm. 100mA, 200mA, 250mA, 1021 For model 0240 1' 420 PS 23 D.I.N. 5 Pin 180° 0.20 RECORD STORAGE/
500mA. 1A, 1.5A. 2A 1022 For model 0240 6," 42p PS 24 D.I.N. 5 Pin 240° 0.20 CARRY CASES
QUICK -BLOW Op each. PS 25 Jack 2.5mm Plastic 0.16 hin EP. 181in x 7in x Sin (50 records)
50 For model X25 48p 12.10
PS 26 Jack 3.5mm Plastic 0.16 12in LP. 131in x 71in x 12.1in (50 records)
EARPHONES 51 For model X25 1' 48p
PS 27 Jack r Plastic 0.30 S2.95
Crystal 2.5mm plug 421, 52 For model X25 489 PS 28 Jack 1' Screened 0.35
Crystal 9.5mm plug 42p PS 29 Jack Stereo Plastic 0.30
8 ohms 2.5mm plug 22p ELEMENTS PS 30 Jack Stereo Screened 0.38 CASSETTE CASES
8 ohms 3-5mm plug 22p ECN 240 11410 ECCN 24011.32 PS 31 Phono Screened 0.18 Holds 12. 10in x 31in x 510. Lock and
EX 2511.18 handle, 1140.
EG 24011.07 PS 32 Car Aerial 0.22
DYNAMIC MICROPHONES PS 33 Co -Axial 0.22
131223. 200 ohms pins on/off mote)) and SPECIAL PURCHASE
2-5mm and 3.5mm plugs 11.85 ANTEX HEAT SINKS 10p SOCKETS 288055. Silicon Power Transistors NPN.
PS 35 D.I.N. 2 Pin (Speaker) 0.08 Famous manufacturers out -of -spec devices
3 -WAY STEREO HEAD- VAT included in all prices. Please add PS 36 D.I.N. 3 Pin 0.11 free from open and short defects -every one
10p P. & P. (U.K. only). Overseas orders - PS 37 5 Pin 180° 0.11 ablel 115W. T03. Metal Case.
PHONE JUNCTION BOX please add extra for postage. PS 38 D.I.N. 5 Pin 240° 0.11 OUR SPECIAL PRICE 8 for 21
H1012 81417
PS 39 Jack 2.5mm Switched 0.12

2 -WAY CROSSOVER NEW COMPONENT PAK PS 40 Jack 3.5mm Switched 0.12 LOW COST CAPACITORS
PS 41 Jack 1' Switched 0.20 0.01/.iF 400V. 8p each
NETWORK BARGAINS PS 42 Jack Stereo Switched 0.30 500µF 50V. Elect. 10p each
K4007.90 ohms Imp. Insertion loss 3bB 11.21 Pack PS 43 Phono Single 0.08
No. Qty. Description Price PS 44 Phono Double 0.10
REPANCO TRANSFORMERS
CAR STEREO SPEAKERS Cl 200 Resistors mixed values approx PS 46 Co -Axial Surface 0.10
240V. Primary. Secondary voltages avail-
t Angled) 13.85 per pair. count by weight 0.55 PS 47 Co -Axial Flush 0.20
able from selected tappings 4V, 7V, 8V, 10y,
C2 150 Capacitors mixed values approx 14V, 15V, 17V, I9V, 21V, 25V, 31V, 33V,
count by weight 0.55 LEADS 40, 50 and 25V -0-25V.
BI-PAK C3 50 Precision Resistor» 0.1%, 0.01.
mixed values 0.55
LB 1 Speaker Lead 2 pin D.I.N. plug to Type Amps
open ends approx 3 metres long MT50/1
Price P. & P.
1 11418 30p
(coded) 0.20 MT50/1 1 12.42 852
CATALOGUE AND LISTS C4 75 Ith W Resistors mixed preferred
values 0.55
MT50/2 2 13.30 40p

Send S.A.E. and 10p. C5 5 Pieces assorted Ferrite Rods 0.55 CABLES
C6 2 Tuning Gangs, MW/LW VHF 0-55
CP I Single Lapped Screen 0.07 CARTRIDGES
CP 2 Twin Common Screen 0.11 ACOS
INSTRUMENT CASES C7 1 Pack Wire 50 metres assorted
colours 0.55
CP 3 Stereo Screened 0.12 GP91-113C 200mV at 1.2cm/eec 11.86
CP 4 Four Core Common Screen 0.28 GP93-1 280mV at lcm/sec 1145
C8 10 Reed Switches 0055 PC 5 Four Core Individually Screened 0.30 GP96-1 100mV at 1cm/sec 1240
C9 3 Micro Switches 0-55 CP 8 Microphone Fully Braided Cable 0.10 J-2005 Crystal/Hi Output 11.05
J -2010C Crystal/HI Output Compatible 1140
CIO 15 Assorted Pots & Pre -Sets 0.55 CP 7 Three Core Mains Cable BOO
J-20068 Stereo/Hi Output 11.75
CII 5 Jack Sockets 3 X 3.5m 2 x CP 8 Twin Oval Mains Cable 0.07 J-2105 Ceramic/Med Output 11.115
(Black Vinyl covered) Standard Switch Type 045 CP 9 Speaker Cable 0.05 J-2203 Magnetic 5mV/5cm/sec, including
0.18 stylus 0446
No. Length Width Height Price C12 30 Paper Condensers preferred types CP 10 Low Loss Co -Axial
J -2203S Replacement stylus for above 13.00
BV1 8' x 51' x 2' 1140 mixed values 0.65 AT -55 Audio-technica magnetic cartridge
BV2 I x x 3' 111.45 C13 20 Electrolytics Trans. types 0.55 CARBON 4mV/5cmiliec 13410
ALUMINIUM BOXES C14 1 Pack escorted Hardware- POTENTIOMETERS
Nuts/Bolts, Grommets, etc. 0.55 Log and Lin
BAI 51* x 2r x II' 42p 4.7K, 10K, 22K, 47K, 100K, 220K, 470K, CARBON FILM RESISTORS
10A2 x 4' x 11" 42p C15 5 Mains Slide Switches 0.55 The E12 Range of Carbon Film Resistors,
BA3 V x 2r x li" 42p C16 20 Assorted Tag Strips & Panels 0.55
1M, 2M
Single Lege Switch
watt available in PAKS of 50 pieces,
BA4 51' x 4' x 11' 50p VC 1 04.11
assorted into the following groups:
2r 2' C17 10 Assorted Control Knobs 0.55
BAG
BA6
BA7
r7'
4' x
x
x
2'
x
x
x
1'
2;"
42p
94P
70p
C18 4 Rotary Wave Change Switches 0.55
VC 2
VC 3
Single D.P. Switch
Tandem Less Switch
0478 RI 50 Mixed 100 ohms --820 ohms
0-46 R2 50 Mixed lk 0-8-2k 0
046 R3 50 Mixed 10k O -82k0
Sop
60P
502
3' C19 2 Relaye 6-24V Operating 0.55 VC 4 1K Lin Less Switch
BA8 8' x x 90p
VC 5 100 K anti -Log 11.48 R4 50 Mixed 100k CI -1M II 50p
4' x 2' 58p C20 1 Pack Sheets of Copper Laminate THESE ARE UNBEATABLE PRICES -
P. & P. 10p on each box approx. '20 sq. ins. 0.55 JUST 1p EACH INCL. V.A.T.
HORIZONTAL CARBON
VISIT OUR COMPONENT SHOP PRESETS
0.1 watt 0.08 each BI-PAK SUPERIOR QUALITY
18 BALDOCK ST., WARE, Herts. (A10) 100, 220, 470, 1K, 22K, 4-7K, 10K, 22K, LOW - NOISE CASSETTES
Open Mon. -Sat. 9-5.30 p.111. Tel. 61593 47K, 100K, 220K, 470K, 151, 2M, 4.7M (260, 36p; C90, 48p; C120, 80p.

10 Practical Electronics January 1975

 the lowest prices !
BI-PAK QUALITY COMES TO AUDIO!
AL10/AL20/AL30 AUDIO NOW WE GIVE YOU ,esse
es,
50w PEAK (25w R.M.S.)
AMPLIFIER MODULES dl

The ALIO, AL20 and AL30 unite are

PLUS THERMAL PROTECTION !
similar in their appearance and in their
general specification. However,
selection of the plastic power devices has
careful The NEW AL60 Hi-Fi
resulted in a range of output powers from
3 to 10 watts R.M.S.
The versatility of their design makes them
Audio Amplifier FOR ONLY £395
Ideal for use in record players, tape recorders,
stereo amplifiers and cassette and cartridge Max Heat Sink temp 90°C. Thermal Feedback
tape players in the car and at home.
Frequency Response Latest Design Improvements
Parameter Conditions Performance 20Hz to 100KHz Load - 3, 4, 8 or 16 ohms
HARMONIC DISTORTION Po 3 WATTS I ... 1KHz 0/5% Distortion better than Signal to noise ratio 80dB
0.1% at 1KHz Overall size 63mm x 105mm
LOAD IMPEDANCE - 8-160 Supply voltage 15-50 volts x 13mm
INPUT IMPEDANCE f 1KHz 100 ha Especially designed to a strict specification. Only the finest components
FREQUENCY RESPONSE -3dB Po 2 WATTS 50 Hz 25KHz have been used and the latest solid state circuitry incorporated in this
powerful little amplifier which should satisfy the most critical A.F.
SENSITIVITY for RATED 0/P Vs =25V. R1=80 1=1K11. 75mV. EMS enthusiast.
DIMENSIONS - 3- X 24' I" STABILISED POWER
The above table relates to the ALIO, AL20 and AL30 MODULE SPM80
modules. The following table outlines the difference.
in their working conditions. SPM80 is especially designed to power 2 of the AL60
Amplifiers, up to 15 watt (r.m...) per channel simul-
Parameter taneously. This module embodies the latest components
ALIO ALSO ALSO and circuit techniques incorporating complete short
Maximum Supply Voltage 25 30
circuit protection. With the addition of the Mains Trans-
30 former BMT80, the unit will provide outputs of up to 1.5
Power out for 2% T.H.D. 3 watts amps at 35 volts. Size: 63mm x 105mm x 30mm.
5 watts 10 watts These unite enable you to build Audio Systeme of the highest
(RL 80 f = 1KHz) EMS MM. EMS Min EMS Min. quality at a hitherto unobtainable price. Also ideal for many
other applications including: -Disco Systems, Public Address,
AUDIO AMPLIFIER PRE -AMPLIFIERS Intercom Units, etc. Handbook available lop PRICE L325
MODULES PA 12. (Use with ALIO, AL20 TRANSFORMER BMT80 L215 p. & p. 28p
AL 10. 3 watts 68.60 and AL30) 64.36
AL 20. 5 watts 1245 PA 100. (Use with ALSO) 218.16
AL 30. 10 watts 63.20
STEREO PRE -AMPLIFIER TYPE PA100
TRANSFORMERS Built to a specification and NOT a price, and yet still the greatest value on the market,
POWER SUPPLIES T461 (Use with ALIO) 11.130 P & P 15p the PA100 stereo preamplifier has been conceived from the latest circuit techniques.
PS 12. (Use with ALIO, AL20, AL30) 95p T538 (Use with AL20, AL30) SS SO P & P Designed for use with the ALSO power amplifier system, this quality made unit incorporates
BPM 80. (Use with ALSO) 63.25 15p no teem than eight silicon planar transistors, two of these are specially selected low noise
FRONT PANELS FP 12 with Knobs 11MT80 (Use with ALSO) MTh NPN devices for use in the Input stages.
01.00 P & P 25p Three ,witched stereo inputs, and rumble and scratch filters are features of the PA100,
which also has a STEREO/MONO switch, volume, balance and continuously variable
PA12 PRE -AMPLIFIER SPECIFICATION base and treble controls.
The PA12 pre -amplifier has been designed to match into Frequency reeponee- SPECIFICATION
most budget stereo systems. It I, compatible with the 20Hz-50K Hz ( - 303 ) Frequency Response 2011z-20KHz 4- ldli
Bass control- Harmonic Distortion better than ff 1%
AL 10, AL 20 and AL 30 audio power amplifiers and it I2dB at 60Hz Inputs: 1. Tape Head 3.25 my into 50K 11
can be supplied from their associated power supplies. Treble control- 2. Radio, Tuner 75 mV into 50K n
There are two stereo inputs, one bas been designed for use ± 14dB at 14KHz 3. Magnetic P.C. 3 mV into 50K fl
with *Ceramic cartridges while the auxiliary input will *Input 1. Impedance All Input voltages are for an output of 250mV. Tape and P.U. Inputs
suit moat }Magnetic cartridges. Full details are given in 1 Meg. ohm equalised to RtAA curve within ± 1dB. from 20Hz to 20KHz.
Bass Control ± 15dB at 20Hz
the specification table. The four controls are, from left to }Input 2. Sensitivity
Impedance
300mV
Treble Control ± I5dB at 20K Hz
right: Volume and on/off switch, balance, base and treble. 30 K ohm, Filters: Rumble (High Pass) 100Hz
Size 152min x 89mm x 35mm. Sensitivity 4mV Scratch (Low Pass) 8KHz
Signal/Noise Ratio better than -65dB
Look for our Input overload + 20dB
Supply + 35 volts at 20mA
SEMICONDUCTOR ADVERTISEMENTS in Dimensions 292mm x 82mm x 35mm
Practical Wireless Wireless World Radio Constructor ONLY L1315
ALL PRICES INCLUDE V.A.T. MK 60 AUDIO KIT
Comprising: 2 x AL60, 1 x SPM80, 1 X BTM80, 1 x PA 100, 1 front panel, 1 kit of
parts to include on -off switch, neon Indicator, stereo headphone sockets pine instruction
The STEREO 20 booklets. Complete Price: 688.76 plus 30p postage.

TEAK 60 AUDIO KIT

The "Stereo 20" amplifier is mounted, ready wired and tested Comprising: Teak veneered cabinet size 162" X 111- X 31', other parts include aluminium
on a onepiece chassis measuring 20 cm x 14 cm x 5,5 cm. chassis, heataink and front panel bracket. plus hack panel and appropriate sockets, eta.
This compact unit comes complete with on/off ((witch Kit price: MSS due 30p posta e
volume control, balance, bass and treble controls,
Transformer, Power supply and Power amps. Giro No 388-7006
Attractively printed front panel and match-
ing control knobs. The "Stereo 20" has been Phase send all orders direct to warehouse and despatch department
designed to fit into most turntable plinths
without interfering with the mechanism or,

131-PAK
alternatively, into a separate cabinet.
Output power 20w peak. Input 1 (Cer.)
300mV into 1M. Freq. res. 25Hz-25kHz.
Input o (Aux.) 4mV into 30K. Harmonic
distortion. Bass control ± 12dB at 60Hz
typically ff 25% at 1 watt. Treble con.
± 14dB at 14kHz.
ii4.45
TC20 TEAK VENEERED CABINET
For Stereo 20 (front board undrilled) Size our x 81' X 3', 13.116 plus 30P postage.
SHIM STEREO HEADPHONES
P.O. BOX 6, WARE HERTS,
Postage and packing odd ISp. Overseas add extra for airmail.
4-16 ohms impedance. Frequency response 20 to 20,000Hz. Stereo/mono switch and volume
controls, 14.96 Minimum order 55p Cash with order please.
Guaranteed Satisfaction or Money Back

Practical Electronics January 1975 11

 TVALVE MAIL ORDER CO.
CRESCENT RADIO LTD. RS
I6a WELLFIELD ROAD, LONDON SWIG 2BS
SPECIAL EXPRESS MAIL ORDER SERVICE
Express postage Sp for first later, I p thereafter, over
11-15 & 17 MAYES ROAD, LONDON N2.2 6TL ten post free. INTEGRATED CIRCUITS 6p + Ip each added
(also) 13 SOUTH MALL, EDMONTON, N.9 Sp Is 29 As
1E21 0.17 FAZ11 1.16 BY213 046 OAZ203 045 28170 0.10
APZ12 2.00 BYZ1O 046 0A.2206 045 Z8271 0.18
MAIL ORDER DEPT. 1N23
1N135
0.85
048 A0Y28 0.25 BYZ11 040 OAZ20 045 ZT21 045
II MAYES ROAD, LONDON N22 6TL 131253 0.60 A81(27 0.30 BYZ12 0.40 OAZ208 0.40 ZT43 045
AO Y28 0.25 BYZ13 045 OAZ209 040 ZTX107 048
Phone 888 3206 & (EDM.) 803 1685 1N256
1N646
0.50
046 ASY29 040 BYZ13 145 OA Z210 040 ZTX 108 0.10
IN726A 040 ASY36 046 8E216 00.0 OAZ211 040 ZTX300 0.14
ADD LUXURY "CRESCENT" 100 WATT R.M.S. 1N914 0.08 AS Y50 040 13Z1(88 0'10 0.42222 0.45 ZTX304 044
AS Yt.il 0.40 OAZ223 0.46 ZTX500 045
TO YOUR CAR ALL PURPOSE AMPLIFIER 1E4007 0.12 A8Y53 1320 0111 0.55 0AZ224 0.45 ZTX503 046
WITH A MOTOR DRIVES CAR U . BUILD. IT 18113 045 ASY55 0.80 CR01/05 0.30 OAZ241 0.26 ZTX531 0.25
18131 0.18
AERIAL We supply the three modules for you to build 18202 0.28 A8Y62 0.25 CE01/40 845 OAZ242 046
Spec.: S Section this Disco-Group-P.A. amplifier into the cabinet 20371 0.40 A13156 803 01:14B 1.90 OAZ244 0.25 INTEGRATED
Extended Length 100cm of your choice. A8Z21 1.00 081011 3.50 OAZ246 0.16 CIRCUITS
Length under Fender 40cm 20381 0.22 DD000 0.15 OAZ290 048 7400
* THE POWER AMP MODULE 20414 0.80 A8Z23 0.75 040
Cable Length 120cm AU101 1.50 DD003 0.15 0018 1.00
Supplied complete with Fixing 170W r.rn.s. sq. wave 300W instantaneous peak 20417 046 AUY10 1.00 DD006 025 0016T 1.00
7401 0.20
0.20
Bracket and :7.50 plus into 8 ohm (80W into 16 ohm). 2E404 0.22
BC107 812 DD007 0.40 0019 040 7402
Control Switch. (.6 P. * THE PRE -AMP MODULE 231897
231698
0.16
040 BC108 0.12 DD008 0.38 0020 240 7403
7404
0.20
040
Four control pre -amp, Vol. Bass, Treble. Middle 80109 812 6113 833 0022 1.00 7405 0.20
controls. Designed to drive most amplifiers 01706 0.10 BC113 816 0D4 0.10 0023 1.26
using F.E.T. first stage. 2N706A 042 140118 1320 0.10 0024 1.10
7406 0-40
3N708 0.16 gEt 0.25 7407 0.40
* THE POWER SUPPLY 2E709 0.40 130116 020 0025 0.40 7408 045
Is supplied complete with the mains transformer. BC116A 823 01)12 0.10 0026 040
2E1091 0.65
180118 020 011T102 0.50 0028 0.70
7409 048
Complete fixing instructions are supplied and no 3141131 046 GET103 040 0029 046 7410 0.20
technical knowledge is required to connect the 3311132 0.26 B0121 0.20 7411 048
80122 (320 GET113 0.85 0030 040
three ready wired modules. A fantastic bargain. 3311302 0.18 GET114 0.30 0035 0.55
7412 0-28
"CRESCENT 125, care. 75p. Send B.A.E. for further details 2E1303 0.18 BC125 0.68 7413 040
BEAT BRITS" 180128 865 GET115 875 0030 085 7418 040
SINGLE on this or our ready built amplifiers. 2N1304 042 GET116 885 0041
2E1305 0.22 BC140 855 0.35 7417 040
cre,Stmt CHANNEL BC147 ' 0.50 0042 0.40 7420 0.80
beat - SOUND TO 12-0-12V 500M/A 2E1306 048 80140 810 GET872 0.30 0043 0.70
LIGHT UNIT 240V primary transformer bargain. Approx. size: 2N1507 048 BC149 812 OET875 840 0044 048 7422 0.28
britc 2N1808 0.28 7423 040
,t4 This fantastic 60mm X 40mm x 50mm: fixing centres: 75mm. BC157 814 GET880 0.55 004431 0.17
little box Our price 8140. 9N2147 0.76 GET881 0.25 0045 94.8 7425 047
2E2148 0.60 80158 012 7427 047
approx. 4' x 3' x 2i' when I8V 500M/A 2312160 1.00 BC160 0.88 6ET882 835 004531 0.18 7428 048
connected to the output of a 240V primary. Approx. size: 60mm x 40mm x 2142218 0-U BC169 014 GET085 0.40 0046 0.27 7430 0.20
sound source from 1 to 100 watts 60mm. fixing centres: 75mm. Our Price 111 each BCY31 0.46 GEX44 0.08 0057 0.60
2N2219 046 7432 027
produces a psychedelic light 2N2389A 0.16 BCY32 1.20 GEX45/1 046 0058 0.60 7433 0.48
display of up to 1000 watts. BARGAIN BOX 2N2444 1.99 BCY33 0.3g 0E1941 046 0048 040 7437 048
Complete with a sensitive level Loud buzzer mounted in a metal box complete 2N2613 0.28 BCY34 0.46 0.73111 0.60 0068 040 7438 048
control the unit is fused and can- with two U2 battery size holder. 2142646 0.60 /301(38 0.66 Wed 0.50 0070 0.18 7440 040
not harm your amplifier. Designed and can be used as a fire alarm but is 2312904 0.20 B0139 1.00 03014 0.25 0071 0.15 7441AN 046
A Bargain at 37.50 plus 10p. ideal as a door or morse code practise buzzer. 1N2904A 0.25 BCY40 0.80 0 ./711 050 0072 0.26 7442 0.85
Approx. size: 2Iin x 64in x llin. 080 H01005 850 0073 0-60
2312906 0.20 BCY42 0.20 0074 080
7450 040
MINIATURE RELAYS OUR PRICE 50p 3312907 049 100170 815 3113100A 7451 0.20
Brand new range of British made 2N2924 0411 BCY71 (320 MAT100 0.20 0075 040 7463 040
ABS PLASTIC BOXES 0.60 MAT101 825 0076 0.80
relays, size: liin X lin X fin. Handy boxes for construction projects. Moulded 2312925 0.16 BCZ1O MATI20 820 0077 1355
7484 0.20
All two changeovers with 250V 2E2926 0.10 BCZ11 0.65 7460 0.80
extrusion rails for P.C. or chassis panels. Fitted 1.00 MAT121 025 0078 046
1.5A contacts and suitable for with lmm front panels. 1005, 105mm X 73mm X 2143054 0.50 BD121 MJE520 0.66 0079 040
7470 NM
fitting on 131m veroboard. 45mm 51p; 1008, 150mm x 75mm X 47mm 88p; 2313055 0.80 BD123 1.00
1.10
Type Volts Current Ohms 1007, 184mm x 124mm x 60mm ellp; 1021, 2143702 0.11 BD124 880 MJE2955 OC81 0-28 772 r4(84
1.45 MJE3055 0.75 00811) 048
27/A 12V 1731/A 700 All 106mm X 74mm x 45mm (sloping front) 60p. 2143705 0.16 BDY11 0.22 31JE340 0.50 00811d 040
7474
7473
0.48
21/A 12V 2831/A 430 1110 2143706 0.11 BF115 MPF102 0.40 0C81DM 0.18 7476
049
12/A 6V 3351/A 185 each BARGAIN BOARDS 2143707 048 BF117 1350
0.25 MPF103 040 00812 045 7480
046
200/850V Mains Relay Components galore for the experimenter. Ex - 2/43709 0.10 8E167 045 048
040
Heavy duty contacts 2,500 ohm 2E3710 0.11 8E173 828 MPF104 0082 7482 047
coll. All new and unused Computer boards with resistors, capacitors and 2313711 0.11 8E181 9 MPF10 0.46 00820 045 7483 1.20
useful transistors -at least 4 transistors per board. 8E184 0.2285 NKT1285 0.45 0083 0.25 7484
D.P.D.T. mains relays 60s, Carr. 2313819 045 1.00
free. Special quantity 840 per Five boards D. 2E4289 0.20 BF185 822 NKT129 040 0084 0.30 7486 040
100 off. 131,194 0.13 NKT211 0.25 1338 7744906
0.75
2N9027 0.58
2in. PANEL METERS 2E5088 0.88 13F195
BF198
0.18 NKT213
815 NKT214
0.25
0.24
7491A 140
MIDGET 28301 0.50 0.76
Size 59mm x 46mm 28804 1.15 BF197 815 NKT216 00.40
40 0° C0 00 11322823 011. 4208 77,4yN 0.76
MAINS TRANSFORMER 060µA -11118 0.100mA-31E13 28501 0.76 BFE161 825 NKT217 0.86
0.100/.1.4.-31E7 0.500mA-31E14 1331398 0.25 NKT218 046
Varnish Impregnated 28709 1.00 NKT219
0.500µA-ME8 0.1A -ME1S AA129 040 BFX12 820 COO
Size 45mm x 36mm x 31mm 0.1mA -ME9 BFX13 0.24 NKT222 825
0.50V a.c. -ME16 AAZ12 0.76 NKT224
00.285 0 00170171 4.82
PRI 240V 0.5mA -MEIO 0.300V a.c.-ME17 AAZ13 040 BFX29 828 848
Sec 3.0.3 100mA 0.10mA-MEll 8 meter -31E18 BFX30 828 NKT251 00.2204 0002020001 5
0.010 041
£0107 0.86 898 NKT271
Sec 8.0.6 100mA 0.50mA-ME12 V.U. meter -21E19 AC128 0.26 BFX33 74110 047
Sec 9.0.9 100mA BFX6J 850 NKT272 0.20 00202 0.9 048
Sec 12.0.12 100mA L3 each. 10p P. a P. A0127 046 BFX84 825 NKT273 820 00203 04
AC128 0.20 1.00
Sec 20.0.20 100mA AC187 040 BFX8., 0.28 NKT274 0.2000204 045 774411:91 142
21.28 10p P. & P. POWER PACKS AC188 040 BFX86 825 NKT275 072200: 110000 74121 0.57
PP1 Switched 3-6-75-9V 400M/A Transistor and BFX87 0.25 NKT277 0002.62205
00208 1.10 74122 0.80
Zener Stabilised On/Off switch and Polarity ACY17 0.85 822 NKT278
CRESCENT BUBBLE LIGHT SHOW AOY18 0.27 BFX88 74123 144
Reversal switch, in a black metal case, 1.00 NKT301 0.86 00480 0.*0
This budget system compares very 6645 each. ACY19 047 BFY1O 0.50 NKT304 0'75 00470 04-0
74141 1.00
favourably with more sophisticated
PPS Switched 6.71-9V Battery Eliminator. AOY20 042 BEY11
BEY17 0.40 NKT403
144
and higher priced models. AOY21 0.82 2.30
Specification: Approx. size 2Iin x 2118 x 3Iin. Ideal for ACY22 0.18 liFY18 0.45 N KT404 040 ORP12 spa. 74151 1.15
convection cassette recorders, AGNS each (Philips type BFY19 0.50 NKT678 1.41
0.
Projector -150W 2840). ACY27 046 0,45 NKT713
00.-8700 0°CRPP7610
81471 7774441142
74153
4550 2.30
cooled. At 30ft the projected ACY28 045 BFY24 08.2800 0.0.2420
1.15
image is 16ft. PP3 Car converter. From 12V Pos. or Neg. to ACY39 045 BFY44 1.00 NKT773 145
Motor -1 rev. per 2 min. = 6-71-9V. Easy to fit and transistor BEY50 0.20 NKT777 048 8X631 046
regulated, 9240 each. AOY40 0.22 078B 7415774156 1.09
Liquid Wheel -Sin diameter AOY41 0.22 BF1(51 0.20 2.88
multi colour. AOY44 042 13FY52 820 0.45 00:13380 88/664305 0.0156 74170
The motor is fitted to the projector 3 KILOWATTS PSYCHEDELIC AD140 0.60 BEY33 817 0A8 1 80
and can only be purchased as a LIGHT CONTROL UNIT ADID 040 BEY64 0.45
0.75
0A47
0A70
048 01642 040 74173 1.29
single unit. AD161 0.89 BFY90 8X644864 144
The liquid wheel is our standard AD169 B8X27 0.50 OA71 040 8X845 045 74190 230
0.119 0A73
model and may be purchased AF1011 0.80 BEIX60 893 0'15 TIC44 049 74191 2.30
separately. 138X76 0.18 0A74 0.15
0.10 1. 15/30P 0.75 7419,
AF114 046 0.17 0A79 2.30
A bargain at: Projector, 216; AF115 0.0 B8Y26 0.20 0A81 0.10 V30/201P 0.76
74193 230
Wheel, 16; Total LW. Plus 75p AF116 046 BBY27 0.50 0A85
care. AF117 040 MEM 0.12 0A86 00155 Vv860°/1220°1P 007505
74194 1 72
AF118 040 1313Y95A 74193 1.44
7in x 4in LOUDSPEAKER Three Channel: Bass, Middle, Treble. Each BSY95 0.12 0A90 0.07 XA101 040
channel has its own sensitivity control. Just AF119 040 0A91 807 XA102 0-18 74196 1.58
A top quality connect the input of this unit to the loudspeaker AF124 0.80 81'102/500R
speaker ideal where 0.75 0A95 0.07 XA151 045 74197 1.58
terminals of an amplifier, and connect three 250V AF128 0.80 0A200 0.08 XA152 045 74198 848
small size is import- AF126 0.80 BTY42 0.92
ant. Manufactured up to 1000W lamps to the output terminals of the BTY79/10OR 0A202 0.10 XA161 0.25 74199 248
by E.M.1. for a well- unit, and you produce a fascinating sound -light £7197 0.80
0.75 0A210 0.20
display. (All guaranteed.) AP189 0.88 XA163 0.85
known hi-fi set AF178 0.55 BTY79/400R 0A211 025 XB1OI 048 Plug in sockets
maker. Size: 7iii x C18 -SO plus 38p P. & P. £7170 045 140 OAZ200 040 -low profile
4in. Impedance: 8 ohms. Flux: 111,100 0.15 OAZ201 845 XB102 0.80 14 pin DIL
38.000. Max. Free range: 90Hz to
£7180 0.65 96
MINI LOUDSPEAKERS AF181 0.60 BY 126 0.14 OAZ202 045
12kHz. Power handling: 5W. AF186 040 BY127 0.15 OAZ203 18 pin DIL
Unbeatable. Price: 011.80. Free 21in 80 ohm. 50p; 21in 40 ohm, 600. Please
X8121 048 047
postage on this item. include 5p P. & P. on each L.8. AFT 19 1.18 BY 182 0.85 OAZ204
Open daily to callers: Mon. -Fri. 9 a.m.-5 p.m.
U.K. CARRIAGE I VAT SEND 20p FOR A Valves, Tubes and Transistors Closed Sat. I p.m. -3 p.m. Prices cornet
I Sp UNLESS 130/0 VAT TO BE ADDED CRESCENT Terms C.W.O. only Tel. 01-677 2424-7 when going
OTHERWISE STATED TO ALL ORDERS CATALOGUE
All orders subject to, V.A.T. at 8% rate. This must
be added to the total order including postage. to press.

I2 Practical Electronics January 1975

 Dept . 2
56, Fortis Green Road, London. NIO 3HN.

JL 0
-FM 0
electronics telephone: 01--883 3705

INDUCTORS TUNING CONDENSERS VEROSOARD

TYPE E TYPE 00

Romeo elexl-41 Coils

Ferrite Rod Aerials
C OPPERC LAD PLAIN EXTRA

0.1" 0.15' P&P

P161 Long & Median Wave bond (3040 84 3 gaff 310p1 208 176 pf 24" . I" 7p 7p
FRA2 Long & Medium (5041) 84 with screen & 24" o 32" 24 2Ip 12p
Tuned Block Filter incorporating a 13.99 men 24" n 5" 30p 25p 13p
OW:MI< lement. Realigned
Tuning Coils in two series £1.48 32" n 31" 30p 25p
to 470 Kb.. 3db bandwidth 5Khz. TYPE C804 34 25p
32" 0 5" 34p :
Rasp Zin 100(. Zout TOOK.
69p 459 10p
839 17" 0 24* 90p
to 40014. 75p 57p 10p
1 150 Wu LP1175 El .46 Slow Motion Drive 17" . 31. £1.21
2 515 14 to 1.545 6.3 Ratio 6:1 R4f: 4511 17" et 5" 99p 10p
3 1.67 Mhz to 5.3 M,3 El .40
151.63 D.I.P. Breactoord 4.15' x 6.15"
4 5 Mu to 30p
to 31.5 Nu I.E.Tmnsfootwn TYPE 0 VEROSTRIP (State .1" or .15")
5 10. 5 Mhz 63p
50 him Pin Insertion Tool (State .1" or .15")
6 30 Mhz to 50 SIP
78 Mhz 10p1 Spot Face Cutter
7 45 Mhz to
15pf 100pf 69p Terminal Pins in Pkts. of 50 Mates .1" Of .15") 2*
50 pi tuning, all others based on 300 pf. WT 13 465 kke Id 6 2nd d/luned 65p 20pf
30596 69p
WI 14 465 Ida find single heed 65p 250
5004 699 Details of I. C.'s; Rectifier's; Diad4s; bridges; Passive
FT 15 10.7 Mhz d/tuned 65p 50pf
Ccenpon.ts; LED's; Clocks; Triacs etc. can be seen
IFT 16 1.6 Mhz 10 6 2nd d/tuned 65p 60pf
365 pf f1.07 cn other pages and/or issues of Wireless Wald; Practical
SerIes A Tronsista - 44 each IFT 17 1.6 Mhz Final alhoned 65p 75pf
100pf 365.365 pf £1.30 Wirlea, and Practical Elecivonics.
IFT 18 465 kla or 1.6 Min 4/toad 75p
Only available in ranges 1 to 5 Inc.
4 Coils cornplete .o rage(
66 6.3V 100 161/ 25V 40V 63V 100/ .1606 450/
110
Blue Aerial Coil
619 sip ISp
4.6119 14 11103 2* 0691 4
Yellow R.F. Intentago 66(28 'OP 111103 1619 06200 1 1p
1.5 619
Osc . Coil for 465 ledu I.E. 66129 11126 14 06202 12p

Electrolytics
Rad 109
2.2 819

*
Ow. Coll for 1.6 Mhz I .F . 674 164 25120
WhIte 14103 lOP 1Y127 OP
3.3 64 16102 27p 1Y133 23p ZS140 299
give mp number lotto, T ' arel colour. 64 846, 17p14F)
444 11164 54 I5141 424
1.110
16115 19p 11176 11.62 15142 3219
6.8 64 619 eW 14144 24 11182 £1 62 ISI70 lop
2Ip
16I45 24 254 I5270 I 1p

\
81250
10 9 16148 22P 10170 27p 25171 16p

22 I:SI 64
649 61
64p
vip 66rp
64
8iP
I 1p
24p) 16.19)
16154
18155
209
154
Series
112Y138 I 1p
IS278
194914
364
4
14156 164 5,4, 114916 10p
33 64 eiv 64 33p(32uF)
BAXI6 10p 0647 I 1p 1144009 7p
47,649 64 64 64 64 tip 15P(50uF) 11104 454 0479 14 144148 54
68 64 64 lip 350/ 181058 414 0481 ep IN4448 99
100 64 64 64 8p 14 259
81100 161p 0665 14 !ZS Series 14
150 64 619 ev lip 14 cwvo W
220 44 64 Bp
330 44 Bp 1 1p 24 449
2943707 1*
470 Bp 1 1p 14 20p 24 47p AC107 1 1(2131. 13p 013V 524 114301 139

680 10p 25p 59p AC126 139 K2141 14 040943 54 I1X302 17p 2943708 14
14P 109
up 24 44 AC127 139 1(268 15p M1480 934 20003 14 2943709 14
14 199 7:4 799
E1.18 ZTX304 2Ip 2943710 lip
AC128 139 BC407 lap MJ481
1500 lap 14 24 AC176 15P 1(170 179 NU490 11.014 Z10311 14 2143711 rep
14 24 39p 44 79p 149p 8C187 24 KY71 7* MJ491 £1.424 200312 10p 2943772 12.00

AD4239
2200
AC 187K 209 1(Y72 170, /41900 £1.424 ZTX341 22p .2N3791 12.55
3300 24 AC188 14 10115 739 M11080 11.22 IT03134 18p 2943819 Dip
4700 25p 44p 689 79p 1499 2529
We dock horn 1,4114 to 19 In11 75p 894p A22953 01.884 ZT0500 12p 2943821 alp
Check I4vels & prices 4.1.0 ordering AA CC188
Y170 39923 10 1n
10124 8049 M13055 £1.21 ZTX501 13p 2143823 99p
ACYI7 384 10131 44 M.14003 V 464 230502 17p 2943903 1619

REGULATORS DIGITAL SWITCH ACY20 24 1013 2 5247 0014010 11.954 210503 14 2143904 19p
601409 484t, 1D1131/2PR 41.17 /41E340 44 ITX504 424 2N3 905
1001.6, 504.4 500A 4149 AUE350 9749 210531 2* 2943906 25.
BCD encoded digital switch 60161 374 10136 434 AUE2955 11.20 ZTX550 17p 2944056 134
(T0-39) (10-31 (501-32) (TO -220) Reading 0 to 9. Suitable la
AD162 3849 10201 11.959 MJE3055 7* 294697 1649 244059 19p
-20°C digital deck clam toning A0161/62MP 74 80202 f1.µ4 MPF102 Vp 194706 14 2144062 14
DVM input tooling 40c. AF114 74 160,107 404 214708 169 2N421)9 199
o .as°c
Al I156
lip239
7 :115 1.91104 109 444 194914 2449 2944441
2*
854
11160 254 MPF 105 444 291930 2944442 11.44
1 to 9. El 49 tech. AF11724 1.99106
AF118 24 MPF I II
17p
17
54p
11167
11173
49p
2*
2941302
2941300
20p
24p
1944443 11.424
2944444 II 2.064
3249 1E178 64 2141304 24p 54
ALUMINIUM BOXES AF124
61139 3449 1E179
2849 MPS1406
3249 MPSU56 77p 1941305 24
2144871
244901 01.414
With Bcatplote and deews AF172 25p 11180 324p C5028 4949 2941306 24 2945067 11.074
SV T1A4256 100501 1129 67239 4049 1E181 3249 0C33 494 2941307 Vp 29451 29 164
(96V15V) ASY26 3249 1E184 274 0(36 4949 2941308 344 2145172 1 1p

£1.03 £1.45 £1.39 97p 42 4 2 K1107 i ip FIE:9485 2749C0(µ14 2911309 MI, 2143191 77p
12V 1146251 103611 1133 5061412 7812050 lip ISp 0C45 14 2941711 26p 2145194 91p
80109 12p 8E195 0(7117p 14p 2941718 14.37 2945295 524
11.03 £1.45 £1.39 97p 12.42 H 2* 10,196 14 0072 14 2941893 5* 2N5447 14
154 T114625C 1017E1 1.14f TDAI415 7815110 K
K117417 °CIS
16p 14 2142218 2* 2N5449 169
WAVIIII5V) BC148 314 CC76 27p 2N7219 384 2945457 463p
41.03 £1.45 11.39 97p 12.42 1(149 :10p°P°P 11181V2"149741 17p °CBI lip 2142646 54 2945458 434
K
aic1,857 13p 1E262 24 OC83 24 2942994 nip 2945159 4349
600mA, 503mA ond 430.4 respectively. 274 2942904
129 1E263 259 0( 170 3249 2145485 5249
REF
14 1E272 11.19 0(171 3249 2942905 394 2945777 484
THYRISTORS SCRs (No.) (1) (WI (9) PRICE POP KIIC19657 17p 0011 01.544 29429 169 2946068 444
K1681 lip 239 ORPI 2 65p 2942925 4 2946069 5149
129209 TIF29
1

A17 24" SI' 14" 45p 5p 1(169 81598BBFFIII1597

534 29429260 10p 7946070 57p
AN 4" 4" 106 459 5, pp 0
80,9/10 439 TIP31 67p 2N3053 I 9p 2N6071 6*
619 4" 22' 14" 'Si' 5P KK 11772 BO< 29 414 319314 67p 2N3054 3019 2146073 67p
6110 4" 31" 11" SIP 5P K177 22p 81088 24 119324 7949 2943055 5149 2946075 E1.µ4
6811 4" 24" 2" 45p 4 K178 229
1E450 2* T1P414 7949 2143375 £3.56; 2946076 16 .re
4812 3" 2" 1" 38p 4 Ng 1E151 270 11P4 24 9749 2N3442 11.19 29461 I I 54
A113 2" 6Ip 7p K
1(1821:98721. lip 8FY90
'1.09 "SO 34 7N3546 14 2946288 64
MC1102 1064
30v 320 39p
6814 7" 24" 74 7p BC1931. 1 2p
16100 42 /, T15 118.6 Mop 21.43638 24 394140 9949
50 106F 44 2N444I 87
AB15 8" 3" 92p 7p 88139 434 11591 3249 2N3702 13p 394141 8749
60v MC11133 44p 1(1841 129
6116 10" 7" 3" 11.05 24 27p 85020 180 210107
103. AC1104 499 1064 44 4117 41" 3" 929 25p
8,K2o4187
2* 110108
2004 MC1120 5Ip 1068 53p 2944442 £1.06
10" 14 10°Pp 2143704M37°3 13p2P 40314312513 54pV1P

A818 12" 5" 3" £1.04 25p 8(209 14 ITY925.4 14 ZTX109 15p 2943705 124 40430 01.39
106D 2N4443 E1.45
1

4133. 67p
600. 1061. 11.50 2944444 [2.09
MI9 12" 8" L1.38 24 K2121 124 8U105/02 01 95; 710300 1* 2943706 14p 40673 55p

OVERSEAS CUSTOMERS DEDUCT 2,17

Vin INCLUSIVE PRICES VAT INVOICES ON REQUEST.

P&P On U.K. Orders min. 15p . Overseas Orders at Cost

13
Practical Electronics January 1975
 R C_V amemene

FOR AUDIO
ON A BUDGET
PUSH BUTTON CAR RADIO KIT
The L.;!itTRY)1!.j.
2547 300 "40 rn
NO SOLDERING
12010 1:3(x)
'Wm
Tourist 11 m
i

111110_ Iva

NOW BUILD YOUR OWN

Technical specification:
PUSH BUTTON CAR RADIO
(1) Output 4 watts R.M.S. output. For 12 volt
Easy to assemble construction kit comprising fully
operation on negative or positive earth.
completed and tested printed circuit board on which
(2) Integrated circuit output stage, pre -built three
no soldering is required. All connections are simple
stage IF Module.
push fit type making for easy assembly.
Controls volume manual tuning and five push
Fine tuning push button mechanism is fully built and
buttons for station selection, illuminated tuning scale
tested to mate with printed circuit board.
covering full, medium and long wave bands.
Car Radio Kit £7.70 + 55p IP ft p Size chassis 7" wide, 2" high and43/4" deep approx
The Tourist I Kit For the experienced constructor Speaker including baffle and fixing strip f1.65+23p.pittp.
If you can solder an a printed circuit board you can build this model.
Same technical specification as Tourist II Car Aerial Recommended -fully retractable
Price £6.60 + 55p p Et p. f1.37+20p. postage Et packing
VIM Atimmet

STER2) QUALITY SOUND

FOR LESS THAN
f,2000
Stereo 21, easy to assemble audio system kit. No soldering required.
The unit is finished in white P.V.C. and the acrylic top presents
an unusually interesting variation on the modern deck plinth.
Includes:- BSR 3 speed deck, automatic, manual facilities together with ceramic cartridge.
Two speakers with cabinets.
Amplifier module. Ready built with control panel, speaker leads and full, easy to follow assembly instructions.
Specifications: For the technically minded:-
Input sensitivity 600mV. Aux. input sensitivity 120mV. Power output 2.7 watts per channel.
Output impedance 8-15 ohms. Stereo headphone socket with automatic speaker cutout. Provision for
auxiliary inputs - radio. tape, etc., and outputs for taping discs. Overall Dimensions. Speakers approx.
151" x r x 4". Complete deck and cover in closed position approx. 15r x 12" x 6".
Complete onlyi19.95 + 11.60 p B p. Extras if required. Optional Diamond Styli £1.37.
Specially selected pair of stereo headphones with individual level controls and padded earpieces to give
optimum performance, f3.85.

BUILD YOUR OWN * 8TRACK HOME CARTRIDGE PLAYER

Elegant self selector push button player
VIt4.""ts STEREO AMPLIFIER for use with your stereo system.
Compatible with Viscount III system,
For the man who wants to design his own stereo - here's your chance to start, Unisound module and the Stereo 21.
with Unisound - pre -amp, power amplifier and control panel. No soldering- Technical specification Mains input,
just simply screw together. 4 watts per channel into 8 ohms. Inputs: 120mV 240V. Output sensitivity 125mV
(for ceramic cartridge). The heart of Unisound is high efficiency I.C. monolithic Comparable unit sold eleswhere at
power chips which ensure very low distortion over the audio spectrum. 124.00 approx. Yours for only
240V. AC only.
f7.64 + 55p pEtp f11.95 + 90p p >r p.

14 Practical Electronics January 1975

 COMPLETE System 1. i51- 00
40 Watt Amplifier. Viscount III - R102 now 20 watts per channel.
System I includes:

STEREO SYSTEM Viscount III amplifier - volume, bass, treble and balance controls, plus switches for mono/
stereo on/off function and bass and treble filters. Plus headphone socket.
Specification
20 watts per channel into 8 ohms. Total distortion IOW r I kHz 0.1%. P.U.1 (for ceramic
cartridges) I 50mV into 3 Meg. P.11.2 (for magnetic cartridges) 4mV I kHz into 47K. equalised
within 1dB R.I.A.A. Radio 150mV into 220K. (Sensitivities given at full power). Tape out
-

facilities: headphone socket, power out 250mW per channel. Tone controls and filter
characteristics. Bass: 12dB to -17dB , 60Hz. Bass filter: 6dB per octave cut. Treble control:
treble - 12dB to -12dB 15kHz. Treble filter: 12dB per octave. Signal to noise ratio:
(all controls at max.) - 58dB. Crosstalk better than 35dB on all inputs. Overload characteristics
better than 26dB on all inputs. Size approx. 13,">9"x 31".
Garrard SP 25 Mk III deck with magnetic cartridge, de luxe plinth and hinged cover.
Two Duo Type II matched speakers- Enclosure size approx. 17;"x 10 rx 6"
in simulated teak. Drive unit 13".. 8" with parasitic tweeter. 10 watts handling.

Complete System £51.00

System 2. £69.00
Viscount III amplifier (As System I)
Garrard SP 25 Mk III deck (As System
Two Duo Type III matched speakers - Enclosure size approx. 27" x 13' x
lli"
Finished in teak veneer. Drive units 13" x 8" bass driver, and two 3" (approx.) tweeters.
20 watts R.M.S., 8 ohms frequency range - 20 Hz to 18,000 Hz.

Complete System f69.00

PRICES: SYSTEM 1 PRICES: SYSTEM 2

Viscount III R102 Viscount III R102

amplifier £24.20 + £1 p & p amplifier f24.20 + f1 p p

2 Duo Type II speakers £14.00 f- £2.20 p & p 2 Duo Type III speakers £39.00 + £4.00 p & p

Garrard SP 25 with Garrard SP 25 with

Mag. cartridge Mag. cartridge
de luxe plinth de luxe plinth
and hinged cover (21.00 + £1.75 p & p and hinged cover f21.00 + £1.75 p&p

total: £59.20 total: £84.20

Available complete for only: Available complete for only:

£51.00 3.50 p Et p f69-00 -,- £4.00 p p

EMI SPEAKERS AT FANTASTIC REDUCTIONS

20 WATT
SPEAKER SYSTEM
System consists of a 13" x 8" (approx)
eliptical woofer unit with a 8' x 5"
(approx.) mid range unit incorporating
aarasitic tweeter and crossover
components.
950
Technical Specification: Ilk KI T
Bass Unit Five matched speakers and crossover unit
Flux density -100 K, speech coil -11 for handling up to 45 watts, frequency
Cone, Triple laminated paper with response from 20 to 20.000 Hz.
P.V.C. surround. Huge 19" 14" (approx.) high efficiency
Mid Range Unit Bass -Speaker with 16.500 -gauss magnet
Flux density -33K, speech coil -1" with built on a heavy diecast frame.
parasitic tweeter. 15" 14A/780 BASS UNIT The four 10.000 gauss tweeters. each 3k"
Power Handling Bass unit on a rigid diecast chassis.
dia. approx.. are fed by the crossover which
20 watts R.M.S., impedance -8 ohms, Superior cone material handles up to 50
critically adjusts signal for maximum
frequency response- 20 Hz to watts RMS. and is treated to give a smooth fidelity. Impedance at 1 kHz is 8 ohms.
18,000 Hz. frequency response. Resonance 30 Hz. flux
Bass coil 2", others 0.5" Recommended
density 360,000 Maxwells. Impedance at
list price 144.00.
OUR PRICE I kHz is 8 ohms. 3" voice coil.
£6.60. Complete Recommended retail price £40.80. Special Offer
90p p p. OUR PRICE f18.70 f150 pap OUR PRICE£19.50-41.50pap
'41111111111111W
111

FOR DISCO PAGE AND DETAILS OF HOW TO ORDER -TURN OVER...

Practical Electronics January 1975

 PORTABLE DISCO CONSOLE
INCORPORATES: Pre -Amp with full mixing facilities, including switched input for mic with
volume control, switched input for auxiliary with volume control, bass and treble controls,
volume control and blend control for turntables.
Two B.S.R. single play professional series decks, fitted with crystal cartridges.
The turntables are designed and precision engineered. They combine clean modern styling
with superb reproduction. Their many special features include square section aluminium
tonearms, (high precision low mass design fully counterbalanced, with calibrated stylus
pressure control for perfect tracking), and conveniently grouped easy to read linear controls.
The turntables have viscous cueing devices which allows the tonearms to be placed or lifted
at any point on the record.
The two lightweight cartridge shells have slide -in -holders to facilitate easy inspection of
needles and cartridges.

TECHNICAL SPECIFICATION :
Pre -amp - Output - 200mV. Auxiliary inputs - 200mV and 750mV into 1 meg. Console size- Unit Closed -171"x 133"x 8 r (approx.)
Mic input - 6mV into 100K. 240 volt operation. Unit Open - 35 rx 13r x 41" (approx.)
Turntables capacity- 7", 10" or 12" records. This disco console is ideally matched for the Reliant IV and Disco 50 or any
Rumble, wow and flutter - Rumble - Better than -35dB. Wow - Better than other quality amplifier.
0.2%. Flutter- Better than 0.06% (Gaumont kalee meter). The unit is finished in black PVC with contrasting simulated teak edging
Finish-Satin black mamplate with black turntable mat inlaid with brushed diamond spun control knobs with matching control panel.
aluminium trim. Tonearm and control. in black and brushed aluminium. Yours for only £45.00 +f3.50 P. b P.

DISCO 50

DISCO AMPLIFIER
Reliant Mk IV Mono Amplifier, ideal for the small disco or house parties.
Outputs 20 watts R.M.S. into 8 ohms (suitable for 15 ohms).
45 WATT R.M.S. MONO DISCOTHEQUE AMPLIFIER Inputs *4 electrically mixed inputs. 3 individual mixing controls.
Ideal for Disco Work. Output Power: 45 watts R.M.S. Frequency Separate bass and treble controls common to all 4 inputs.
Mixer employing F.E.T. (Field Effect Transistors) *Solid State circuitry.
Response 3dB points 30Hz and 18KHz. Total Distortion: less than *Attractive styling.
2% at rated output. Signal to noise ratio: better than 60dB. Bass
Control Range: 13dB at 60Hz. Treble Control Range: 12dB at INPUT SENSITIVITIES
10KHz. Inputs: 4 inputs at 5mV into 470K. Each pair of inputs -Input-i.) Crystal mic. guitar or moving coil mic, 2 and 10mV.
controlled by separate volume control. 2 inputs at 200mV into 470 K (Selector switch for desired sensitivity)..
-Inputs - 2), 3), 4). Medium output equipment - ceramic cartridge, tuner,
Size: 19'-,"x 102" x 8" (approx.) Amplifier £27.50+f1.50 p. Et p. tape recorder, organs, etc. - all 250mV sensitivity. AC Mains, 240V operation.
Size approx: 121"x 6"x 31".
£15.00 + 60p. post Et pack.

BARCLAYCARD IP Radio and TV

Mail orders to Acton. Terms C.W.O. Components
All enquiries Stamped Addressed (Acton) ltd
Envelope. Goods not despatched
outside U.K.
All prices Include VAT at 11% rate
DO NOT SEND 21 High Street, Acton, London W3 6NG
YOUR CARD
Leaflets available for all items liste d 323 Edgware Road, London W2
Just write your order giving thus * Personal Edgware Road: 9a.m.-5.30p.m. Half day Thurs.
your credit card number Send stamped addressed envelope.
Shoppers Acton: 9.30a.m.-5p.m. Closed all day Wed.

16 Practical Electronics January 1975

 SITIWillt Mk Ell-PRE-PAK
Electronic Ignition... Audio Bargains
Better on all points STEREO%
Because you keep your points! DECODER
The SPAR KRI TE MK.2 is a full capacitive discharge electronic system.
Specifically designed to retain the points assembly with all the
advantages and none of the disadvantages. No misfire because contact
breaker bounce is eliminated electronically by a pulse
£4.50inci. P.. P.
suppression circuit which prevents the unit firing it the Ready -built unit, ready for connection to the IF stages of
Points bounce open at high rpm. Contact breaker burn is -

existing FM Radio or Tuner. The very latest 2nd Gener-

eliminated by reducing the current to about 1/50th of
norm, thus avoiding arcing. But you can still revert ation rail less integrated circuit design, operating on this
to bormal ignition if need be. In seconds. If points phase locked loop system, offering even better stereo
go (very unlikely/ you can get replacements separation.
anywhere. All these advantages.
Fitted in 15 minutes. Up to 20% better fuel Only owing to our bulk buying capacity are we able to
consumption. Instant all weather starting. Cleane offer this at the old price. LED stereo indicator lights
plugs they last 5 times longer without attention. available. RED at 2Sp; GREEN at 40p
Faster acceleration. Faster top speeds.
Coil and battery last longer Efficient fuel
47,
burning with less air pollution.
The kit comprises
everything needed
Heady drilled scratch and rust resistant case,
metalwork, cables, coil connectors, printed
3 WR.m.s.I.C. AMP incl. P. & P.
circuit board, top quality 5 year guaranteed
transformer and components, full only £1.50 Order Code I.C.A.I.
instructions to make positive or negative On P.C. Board with all coin or 2
earth system, and 6 page installation on one board for E2.60. Order Code
instruction leaflet. I.C.A.I/S.
WE SAY IT IS THE BEST SYSTEM AT These amps. are supplied with a free book-
ANY PRICE, let on connecting up, specifications and
PRICES easy -to -build projects using the
O I V Kit only (10.53 incl VAT and P L P
Ready Built Unit and VAT and Pb P
1130th to fit all cars with colUdistributor ignition up 10
8 cylindarsi
We can supply units ior any petrol engoned vehicle lboat,
motorcycle atcl with coil/contact breaker ignition
Details on request Call in and see us for a demonstration
5W & 10W AMPS
ELECTRONICS DESIGN ASSOCIATES
(Dept PE1), 82 Bath Street, Walsall WS1 3D E Phone 33652
5W ONLY £1.80
NW ONLY £2.26
CJL PRICES INCLUDE P&P AND V.A.T. incl. P. & P.
These matchbox size amplifiers have an exceptionally good tone
erAERIAL, telescOpic, 15 120cm 01.20 and quality for the price. They are only 21in x IF°. The SW
UAERIAL, telescopic ,h arid v swivel, 15-80cm. .
Amp will run from a 12V car battery making it very suitable
for portable voice reinforcement such as public functions. Two
0EARPHONE , stethoscope style,13 ohm dynamic. £1.00 amplifiers are ideal for stereo. Complete connection details and
treble, bass, volume and balance control circuit diagrams are
ONAND DRILL, (Leytool), Compact precision dri11.5/16" supplied with each unit. Discounts are available for quantity
chuck. Gears totally enclosed.S/L bearings. . . £2.90 orders. More details on request. Cheapest in the U.K. Built
INTEGRATED CIRCUITS
and tested.
DAUDIO POWER AMPLIFIER (National) LM380 £1.00
OA.M.RADIO RECEIVER (RCA) CA3123E £1.40
EIF.M.STERBO DECODER (Motorola)
01/C TIMER (Signetics)
MC1310P £2.80
NE555V £0.78 Now available for 5 &10WAMPS
D.I.L.SOCKETS(pk of 3) 08 pin £0.50 014 pin £0.55
Pre -assembled printed circuit boards 2in 3in
OKEYNECTOR, rapid connect-single/multiple leads to available in stereo only, will fit 0.15 edge connector.
mains.Bui It -in piano switches,neon & 13A fuse. .£3.20
Stereo Pre -Amp I (Pre I). This unit is for use with low
OMICROPHONE , lightweight dynamic ,remote start/stop gain or ceramic pick-up cartridges. £1'10
200 ohms, 100- 10,000Hz ,6mV average output. . £1.80 Stereo Pre -Amp 2 (Pre 2). This unit is for use with
OMULTIMETER, small and attractive, Vdc- 10.50,250 ,
magnetic pick-up cartridges. £155
Stereo Tone Control (STC). This unit is an active

110'I
1,000. Vac -10.50,250, 1,000. !do- 100mA . R - 150k . £4.95
POWER SUPPLY COMPONENTS tone control board and when used with the right potentio-
OSIL1CON BRIDGE RECTIFIER, 100 P.I.V./2A £0.40 meters will give bass and treble boost and cut. £1.10

-
OELECTROLYTIC CAPACITOR, 2,200uF/50V £0.57 Instruction leaflet supplied with all units. Post and
OELECTROLYT1C CAPACITOR, 5,000uF/25V £0.63 packing included in prices.
OSILICON POWER TRANSISTOR. 2N3055 £0.60
VOLTAGE REGULATOR (Fairchild) uA7805 £1,70 1MM EMI
E VOLTAGE REGULATOR (Signetics) NE550A £0.80 PLEASE ADD VAT AT CURRENT RATE
CISIGNAL INJECTOR produces audio through video signals, enclose E
excel lent- servi cing arripl I fiers,radios,te levi sions,etc. £3.92
I for
Decoders/ 3W Amps/ 5W Amps'
OSOLDERING IRON, 25 WATT,(Antex), X25,240V, Very IOW Amps/ Stereo Pre -Amps I

low leakage, 1/8" long life bit( interchangeable). . £1.85 Stereo Pre -Amps 2 Stereo Tone Controls I
03/32"bit £0.45 03/16"bit £0.45 0Element £0.95 (Please insert quantities and delete those not applicable). II
OSTAND,(Antex),ST3,High grade base , chrome plated Name
spring, sponges and accornodation for spare bits. .00.95 Address
OSPEAKER miniature, 8 ohms,70rnm dia. . . £0.80 4/1
BIPREPA
Ca Rogrt No.820919
Dept. A, 1221224 West Road,
Westcliff-on-Sea, Essex SSO 9DF..
Telephone: Southend (0702) 46344.
I
CJL LTD. P.O. BOX 34,CANTERBURY.CT1 PIT
EOM - MINN

Practical Electronics January 1975 I7

 FREE RESIST COATED CIRCUIT BOARD
For every order placed for any of the products listed below, each order will receive a piece of fibre
glass circuit board, approx. size 6in x 6in, coated with negative resist.
DRILLING MACHINES AND DRILL KITS
Specially designed for engineers, lab workers, jewellers. engravers, sculptors, model makers and
hobbyists. These powerful, low power, drilling machines are capable of drilling holes up to 3mm in
diameter in any material. They will DRILL, SAW, GRIND, BURR, BRUSH AND POLISH.
Reliant Drill with 3 collets, 9,000 r.p.m. £3.88 (50p).
Reliant Drill Kit as illustrated 3 collets, 20 tools E8.34 (97p).
Drill Stand, used horizontally or vertically for drilling, sawing, butting, or as a miniature lathe for
turning small components between centres £8.34 (97p).
MAJOR DRILL KIT 'for the man with everything". Contains 9.000 r.p.m. super drill, power unit, drill
stand, 40 assorted tools, presentation box, normally £34.76 only £27.81 (f3.22).
SOLDERLESS MODULAR BREADBOARDS
These DEC breadboards are used throughout the world for making prototype and production
working circuits. The patented contact allows components to be inserted over and over again without
soldering.
S DEC. Discrete components only. Normally £1.98 only £1.32 (25p).
T DEC. Station for one integrated circuit normally £3.63 only £2.43 (39p).
U DEC A. Discrete and I.C. components normally 0.99 only £2.67 (40p).
Each Dec is boxed and has instructions. carriers, plugs. coloured leads are also available
COPPER CLAD GLASS -FIBRE CIRCUIT BOARD
n Single sided normally 85p per sq. ft. only 55p per sq. ft. (29p).
"Ain Double sided normally 93p per sq. ft. only 60p per sq. ft. (30p).
din Single sided normally f1.52 per sq. ft. only 75p per sq. ft. (31p).
qfin Double sided normally £1.60 per sq. ft. only 60p per sq. ft. (31p).
RESIST COATED FIBRE GLASS CIRCUIT BOARD
Coated with positive or negative resist, we will cut fibre glass board to any size asked for, and will
coat with negative or positive resist. The price of resist coated circuit board Is 1p per sq. in.
Example positive or negative coated 4 x 3in 12p each VAT & post. 5 x 5in 25p each + VAT & post. Please quote if positive or negative coated and size.
Ferric chloride 5 litre etchant mix £1.50 (35p). Temperature controlled, air agitated etching tank £85.00 (f6.96). Car Radio, L.W., M.W.. with speaker
£7.50 (64p).
Please add to the sum shown in brackets after the price to cover the cost of post and VAT.

P.B. PRODUCTS LTD.

ELECTRONIC SCIENTIFIC INSTRUMENTS
57 HIGH STREET SAFFRON WALDEN ESSEX CB10 2DP ENGLAND
Telephone: Saffron Walden 22876 Telex: 817201

for fast easy reliable soldering

ASY ITO IME IDIRPAMIAg Lai].)
IDEAL FOR HOME CONSTRUCTORS
IDEAL
Ersin Multicore Solder contains 5 cores of non -corrosive flux, instantly cleaning heavily oxidised
surfaces No extra flux is required.

Fine gauge solder For soldering

SAVBIT handy 1SAVBIT solder ALU-SOL for for soldering small fine joints
solder dispenser for general purpose soldering aluminium Dispensers
components
work New Multicore Alu-sol
of Ersin
Fine gauge solder for soldering Multicore
A coil of Ersin A handy plastic reel of flux -cored solder in 16 small components 138ft of Solder make
Multicore Savbit SAVBIT alloy. 63ft of 18 s.w.g. s.w.g. No extra flux 22 s.w.g. (42.0 metres of those small
Solder in a (19.2 metres of 1.22mm) needed. Plastic reel holds 0.71mm) Ersin Multicore 5 core jobs easier.
dispenser 7ft 6 in of 36ft. Supplied with full solder wound on a plastic reel. 21ft of 22
18 s.w.g. (2.2 instructions. Also available Suitable for intricate work and s.w.g. (6.4
metres of 1.22mm). in solder dispenser. small components. metres of
The Solder that 0.71mm)
reduces the wear
Size 12 £1.72 Size 4 £2.32 Size 10 £1.44 solder,
of soldering iron specially
bits. suitable for
NO soldering tine
wires, small
Size 5 M84%%k components
and for
32p repairing
printed
circuits.
NEW BIB WIRE STRIPPER & CUTTE Ft NEW SOLDER WICK "s%
Size 15 36p
Fitted with unique 8 gauge Absorbs solder instantly, from tags and Or size 19A for kit
selector with handle locking device printed circuits. Only needs 40 to 50 Watt wiring or Radio and
and easy grip handles. Spring soldering iron. Quick and easy T.V. repairs 7ft.
incorporated for automatic to use. Does not need flux and (2.1 metres) of 18
opening. Strips insulation from flex is non -corrosive. s.w.g. (1.22mm)
and cables in seconds and can also Ersin Multicore Solder.
be used as a cutter.
Model 86.70p j Size 18 90p.i Size 19A 34p

Bib Hi-Fi Accessories Limited, Prices shown are recommended retail excluding V.A.T.
From Electrical and Hardware Shops. If unobtainable, send 15p P&P.
Sole U.K.Sales Concessionaires, P.O. Box 78 Hemel Hempstead, Herts. HP2 7EP Prices and specifications subject to change without notice

18 Practical Electronics January 1975

 APPOINTED STOCKISTS FOR SIEMENS QUALITY PRODUCTS

top quality electronic

components for price minded buyers
112p. CATALOGUE FREE POSTAGE (U.K.) ATTRACTIVE DISCOUNTS SPECS. GUARANTEED
A 100 OF THE BEST
From our transistor stock RESISTORS ELECTROLYTIC CAPACITORS
Code Watts Ohms / tog 10 to 179 100 up Aslal Lead
2N1307 47p 13C149C 14p (see note below) uF 3V 6.3V 10V 16V 25V 40V 63V 100V
2742646 51p BC1588 15p 0.47 11p ep
04 nett
lip -
C 1/3 4.7-470K 1.3 1.1
2743053 26p BC159B 1Sp 1.0
-- -- -- 11p Op

- -- -
2743054 60p BC16713 13p C 1/2 4.7-10M 1.3 1.1 0.0 nett 2.2 Op Op
2743055
2743702
1110p
lip
6C18815
EIC1698
BC169C
12p
12p
13p
C 3/4 4.7-1014
4.7-10M
1.5
3.2
1.2
2.5
0.07 nett
1.92 nett
4.7
10 -_ 11p
Op
Op
Op
$p
Op
Op
Op
2743703
2743704
2N3705
10p
lip
10p
BC1798
BCI82L
211p
alp MO 1/2 10-11A 4 3.3 23 nett
22
47
100
Op
Op
- Sp
Op
Op
Op
Op
Op
Op
Op
Op
Op
Op
10p
10p
12p
Op top
13p
lilp
2743794 top BC184L 26p WW 1 22-311C1 11 10 O nett 10p 11p 17p
220 Op Op Op 111p alp
2743819 25p BC212L 12p .WW 3 1-10K 0 I nett 470 Op 10p 10p 11p 13p 17p 240 45p
2744062 lip BC214L 14p
WW 7 1-10K 11 10 O non 1.000 11p 13p 13p 1/p alp 25p 41p
2N4443
2N5052
2145163
52p
42p
20p
BC257A
BC259B
8CY58
14p
14p
30p
Codes:
2.200
4.700
10.000
15p
Elp
42p
11Ip
30p
lip
23p
Sip
211p
44p
3/p
Sep -
41p

27454517 32p BD130 110p

BD131 lap C = carbon film, high stability, low noise.
40361 40p MO = metal oxide. Electrosil TR5 ultra low noise.
40362 44p BD132 52p WW = wire wound, Plessey. MINITRON DIGITAL INDICATORS
40602 411p B0135 37p 311115FSeven segment filament compatible with standard
40636 £136 BD136 351p logic Modules. 0-9 and decimal point: 9mrn characters in
40669 E1.10 BDY20 it3p Values: All E12 except C 9W. C fW and MO 9W 16 lead DIL [1 20
AC128 17p BF194 15p E12: 10, 12, 15. 18, 22. 27. 33, 39, 47, 56. 68. 82 and their Suitable BCD decoder driver 7447 01-15
AC1518 23p BFR39 23p decades. 30150 showing - or - 8 1 8 dec. pt [1.20
AC153 27p BFR79 23p E24 as E12 plus 11, 13. 16, 20 24. 30, 36, 43, 51, 62, 75. 91 and their 25p
0F029
LEDS (Light Emitting Diodes)
AC153K 37p 33p decades. Photo Cells cadmium sulphide each 40p
AC176 24p BFX184 27p
AC176K 36p BFY51 23p
AC187K alp BRY39 45p Tolerances:
5% except WW 10% m 005(1 below 10f1 and MO fW 2%
ANTEX Soldering Irons
AC188K 20p BV164 51p CN340 £1.05 Spare bits 32p
AD133 E1 .02 C10681 42p Prices are In pence each for quentftles of the same ohmic value CCN240 £2.30 Spare bits 40p
A0136 E1.11 C10601 112p and power reUng. NOT mixed valves. (Ignore fractions of one Order it from
AD149 115p C1406 73p penny on total value of resistor order.) Mites for 100 up In units E.V. for de- DESOLDER BRAID
AD161 42p MJ481 E1.20 of 100 only pendable ser- 13tt strip Np
AD162 40p 14.1491 £135 vice.
AF200U 40p M42955 80p WAVECHANGE SWITCHES
AF239 Silp MJE371 lop POTENTIOMETERS CAPACITORS 1 pole 12 way; 2 pole 6 way
E11908 36p MJE521 lip ROTARY, CARBON TRACK
DALY ELECTROLYTIC in cans, plastic 3 pole 4 way; 4 pole 3 way each 29p
BA138 31p MJE2955 E1.12 sleeved TAG STRIP 28 way 11p
B13103 24p MJE3055 Sip 1000mF/25V 28p 2200/100 £1.51
Double wipers for good contact and long 1000/50 41p NUTS, SCREWS, etc.
BB105 34p 0A91 Sp
working life 5000/100 [2.81
138109 lip SD4 Sp 5000/25V Sap 2000/50 87p in lots of 100 each
BC107A 15p TIP31A 70p P.20 SINGLE linear 100 ohms to 4.7 5000/50 E1.18 4BA NUTS Mc 6BA NUTS alp
BC107B 15p TIP32A SOp megohms. each 14p 9" 48 Screws 21p: 9- SBA Screws 24p
POLYESTER TYPE C.2011. Radial loads
BC1088 14p TIP41A Sap P.20 SINGLE log. 4.7 Kohms to 2.2 for P.C.B. mounting. Working voltage Threaded pillars 651A, 9" hexagonal
BC108C 14p TIP42A E1.09 megohms. each 14p 290V d.c. £2.10
8C1096 lip WO2 30p
JP.20 DUAL GANG lin. 4.7 Kohms to 0-01, 0015, 0.022. 0033. 0647. each 3p Plain spacers 9" round £1.46
BC109C lip 2TX300 14p
2.2 megohms. each 48p 088. 0.1. 0- 15 each 4p Other sizes available
8C147A 12p ZTX834 23p 0.47 SP: 0.68 11p; 1.0
BC147B 13p ZTX500 14p JP.20 DUAL GANG log. 4.7 Kohms to 0'22 517; 0' 33 ENAMEL COPPER
14p; 1521p; 2224p
BC148B ZTX504 45p 2.2 megohms. each 411p
12p
SILVERED MICA. Working voltage 500V WIRE In 2 ounce reels
1005 MORE IN CATALOGUE 7 JP.20 DUAL GANG Log/antilog 10K, d.c. 18, 18. 20, 22 SWG 34p
22K. 47K, 1 megohm only. each 411p Values in pFs-2 2 to 820 in 32 stages 24, 26, 28, 30 SWG 40p
BAXANDALL SPEAKER KIT JP.20 DUAL GANG entilog 10K only 469. each Sp 32, 34 SWG 48p. 36. 38. 40 SWG 54p
As designed by P. J. Baxandall and 1000, 1500 7p; 1800 8p; 2200 10p; 2700.
described originally In "Wireless World."
2A DP mains switch for any of above 3600 12p; 4700, 5000 15p; 6800 2pp; 8200. DIN CONNECTORS
14p extra 10,000 25p Socket Plug
Simple to assemble. fantastically good Decades of 10. 22 and 47 only available TANTALUM BEAD 12p
2 way loudspeaker 10p
results and a greater money saver. Carries In ranges above. 0.1, 0.22, 0-47. 1.0 mF/35V. 15/20V. 3 way audio 10p 12p
10 watts RMS, 15 ohms Impedance. Size Skeleton Carbon Presets. Type PR, 3.5/16V each 14p 5 way audio 180 lap lip
18in x 12in x 101n. Complete kit. including horizontal or vertical each Op 2.2/16V, 22/35V, 4.7/16V. 186 3V 5 way audio 240 12p 15p
pack -flat cabinet, E14.90. each 14, 6 way audio 13p 15p
4.7/35V, 10/16V, 22/8.3V each lip
The size and weight of this product obliges 10/25V, 22/16V, 27/8 3V, 100/3V. EV CATALOGUE 7
us to charge 70p part cost of car, in U.K. SLIDER 6.8/25V, 15/25V each 20p 2nd prIntIng-Green and yellow Corer
Equaliser Assembly, £2. 30. Linear or log mono 4'7K to 1 meg. in all POLYCARBONATE 112 pages, thousands of items- illustra-
Loudspeaker Unit 59RM109, t245. popular values each 30p Type 842540 Working Voltage -250V tions; diagrams: much useful technical
Cabinet Kit Ito Baxandall design). 210.45. Values in mF: Information. The 2nd printing has been
STEREO. matched tracks, in. or log. in updated as much as possible on prices.
Cross -over choke for additional woofer to all popular values from 4.7K to 0.0047; 0.0068: 0.0082; 0.01; 0012:0015
each 3p It costs only 25p post free. including
above, £1.50. 1 meg. Kip refund voucher for 25p for spending
0018; 0022; 0.027: 0033; 0039; 0047.
Esgulicghhetognrepylates, mono, black,cnciti:r 0056; 3068. 0.082; 0.1 each 4p when ordering goods list value E5 or
DISCOUNTS CERAMIC PLATE more.
Available on all terns Control knobs, blk/wht/rediyel/grn/ Working voltage WV. d.c. QUALITY
except those shown with blue/dk. grey, It. grey each 7p In 28 values from 22pf to 8800pF. each 2p GUARANTEE
NETT PRICES. 10% on All goods are sold on the
orders from £5 to E14.90. understanding that they con-
15% on orders E15 and All postal communications, mail orders form to manufacturers' speci-
over.
etc. to Head Office at Egham address. fications and satisfaction is
FREE ELECTRMWE LTD Dept. PE1. S.A.E. with enquiries requir-
ing answers.
guaranteed as such -no
rejects, 'seconds' or sub-
standard merchandise is
POSTAGE offered for sale.
In U.K. for pre -paid mail 28 ST. JUDES ROAD, ENGLEFIELD GREEN, EGHAM, SURREY TW20 OHB Prices quoted do not include
orders. For mall orders Telephone: Egham 3603 Telex 264475 Shop hours 9-5.30 daily; Sat. 9-1 p.m. V.A. T. for which 8% must be
for E2 list value and under added to total nett value of
there Is an additional NORTHERN BRANCH: 880 Burnage Lane, Burnage, Manchester M19 1NA order. Every effort is made
handling charge of 10p Telephone (061) 432 4945 Shop hours 9-5.30 daily; Sat. 9-1 p.m. to ensure the correctness of
Overseas orders -ear- information and prices at time
riage charged at cost.
Otro A/C No.
U.S.A. CUSTOMERS are invited to contact ELECTROVALUE AMERICA, P.O. of going to press. Prices sub-
ject to alteration without
38/$71/4002 Box 27, Swarthmore PA 19081. notice.

Practical Electronics January 1975 19

 ALL OUR PRICES INCLUDE V.A.T.
BSR HI-FI AUTOCHANGER R.C.S. STABILISED POWER PACK KITS
All parts and instructions with Zener Diode, Printed Circuit.
E.M.I. 1312 x 8in.
STEREO & MONO Bridge Rectifiers and Double Wound Mains Transformer
input 200/240V a.c. Output voltages available 6 or 9 or 12
SPEAKER SALE!
With twin tweeters.
Plays 12", 10' or 7' record..
Auto or Manual. A high
quality unit backed by BSR
or 15 or 18 or NV d.c. at 100mA or less
PLEASE STATE VOLTAGE REQUIRED.
Details S.A.E. Size 3/ x 11 x 11in. 20p
And crossover. 10
watt. State 3 or 8 or £4.50
15 ohm. As illustrated. Post 25p
reliability with 12 months'
guarantee. AC 200/250V. R.C.S. GENERAL PURPOSE TRANSISTOR With flared tweeter cone and ceramic
Size 131 x 11.1in. PRE -AMPLIFIER BRITISH MADE magnet. 10 watt.
Above motor board 37in. Below motor board 24iu.
with STEREO and MONO XTAL E7.95 Post 45p.
Ideal for Mike, Tape, P.15., Guitar, etc. Can be used with
Battery 9-12V or H.T. line 200-300V d.c. operation. Size:
Bass res. 45-80 c/s.
Flux 10,000 gauss. £2.75
11 x It x 1 in. Response 25 cis to 25 kc(s. 28 dB gain. State 3 or 8 or 15 ohm. Post 25p
For use with valve or transistor equipment. 13 X Sin Bass unit 20 wattr ubber cone surround 15 ohm 2560
PORTABLE PLAYER CABINET instructions supplied. Details S.A.E. £1.25
PatFull

Modern design. Rexine covered. Large front grille.

Lift -up Lid. Chrome fittings. Approx. Hee I7in x lbin x 7in. LOUDSPEAKER FRONT GRILLES
Few only in red rexine.
L450 Post 50 R.C.S. POWER PACK KIT Teakwood strips mounted on cloth backing, easily glued on
Motor board cut for BSR deck

BSR JUNIOR ,------\\

12 VOLT, 750mA. Complete wih printed E2. 0c Post
circuit board and assembly instructions.

NEW TUBULAR ELECTROLYTICS

25p
12 VOLT 300mA KIT, 0215. 9 VOLT 1 AMP KIT. £295.
CAN TYPES
Size 181 in x 100n. 7cr,
-
to bailie to modernise cabinets.
Or size lOtin x Ma. 45P

SINGLE PLAYER 2/350V 14p 250/25V 14p 50+ 50/300V 50p E.M.I. 6. in. HI-FI WOOFER
4/350li 14p 500/25V 209 32 +32/350V 359 8 ohm. 10W. Large ceramic magnet.
Heavy duty 4 -speed motor with Special Rubber cone surround.
separate pick-up arm fitted
LP/78 turnover mono IA cm
compatible cartridge. ("--s Post 25p
1:L:)
8/350V
18/350V
32/500V
229 1000/25V 35p
309 1000/50V
50p I 8 +8/450V
479
229
32 +32/450V 80p
350+ 50/325V 55P
16 +16 +16/275V 45P
Frequency response
10-12,000 c/s. Ideal P.A.
Columns. Hi-Fi Enclosure Systems, etc.
£4
25/25V 10p 8+18/450V 259 32+32-, 32/350V 65p
50/50V 10p 18+18/450V 90p 900/300V 95p Suitable Cabinet 12 x 8 x 8 £4 Suitable Tweeter 02
100/25V 10p 32 +32/350V 40p 4700/63V 95p
LOW VOLTAGE ELECTROLYTICS. ELAC CONE TWEETER
1, 2, 4, 5, 8, 16, 25, 30, 50, 100, 200mF 15V 10p. The moving coil diaphragm gives a good
500mF 12V 15p; 25V 20p; 50V 30p. radiation pattern to the higher frequencies
1000mF 12V 20p; 25V 35p; 50V 97p; 100V 70p. and a smooth extension of total response
2000mF 8V 25p; 25V 42p; 50V 57p. from 1,000 cis to 18,000 c/s. Size 31
2500mF 50V 62p; 3000mF 25V 47p; 50V 85p. 31 x tin deep. Rating 10W, 3 ohm.
5000mP 6V 25p; 12V 92p; 25V 75p; 35V 85p; 50V 95p.
CERAMIC 1pF to 0.01mF, 4p. Silver Mica 2 to 50009F, 9p. Crossover 11.25 LI .90 Post 209.
PAPER 350V-0.1 7p; G5 18p; lmF 15p; 2mF 150V 15p.
R.C.S. DISCO DECK 500V-0.001 to 0.05 4p; 0.1 10p; 0 25 8p; 0.47 25p.
TWIN GANG. "0-0" 208pF r 176pF, £1.10p. GOODMANS
Slow motion drive 38599' + 3850 with 25pF +250.50p;
SINGLE RECORD PLAYER Twin 500pF 75p. Twin 410pF 50p. Twin 1209F 50p.
SHORT WAVE SINGLE. 25pF, 45p; 50pF, 55p. 8 in. WOOFER
Fitted with auto stop. Stereo/mono cartridge. Baseplate. B ohm 12 watt. Deep cone.
Size Olin x 131in. Turntable. Size 7in diameter. A/C mains. SHORT WAVE SINGLE GANG. Precision Silver Plated Heavy ceramic magnet. Bass
200/250V motor has a separate winding 14 volt to power a Gangable Toning Condensers. 100pF. 50P resonance 35 cps. Frequency
small amplifier. Three speeds. Plays all records. response 30-8,000 cps.
Ideal bass unit for £3.75
Hi-Fi system.
£550 25pPost NEON PANEL INDICATORS 250V AC/DC. Amber 309.
RESISTORS. OW, INV, 1W, 20% 1p; 2W, 5p. 1011 to 10M
HIGH STABILITY. IW 2% 10 ohms to 6 meg., 10p.
Ditto 5%. Preferred values 10 ohms to 10 meg., 9p. SPECIAL OFFER LOUDSPEAKERS
SOLID MAHOGANY PLINTH Post 95p WIRE -WOUND RESISTORS 5 watt, 10 watt. 15 watt.
3 ohm, 2tin; 2tin; 31in; Sin.
With P.V.C. Cover. Cut out for moat 10 ohms to 100K 10p each.
8 ohm, 2tin; 2fin; Sin x Sin; 3in; 4in; 5in.
B.S.R. or Garrard decks.
Size 12) x 141 x 7)in. £6.50 TAPE OSCILLATOR COIL Valve type 35p.
FERRITE ROD 8 x tin 20p; 6 x fin 20p; 3 x lin 10p. 15 ohm, 3tin; ,Sin ;18 x 4in; 5 x 3in; 7 x 4in; 8 x
25 ohm, 2tin; 5 x 3in; bin.
35 ohm, 3in; Sin. I EACH
MAINS TRANSFORMERS ALL POST 80 ohm, 2tin; 2fin. 120 ohm 3in.
COMPACT PORTABLE STEREO HI-FI 5p each
250-0-250 80mA. 6'3V 2 amp 42(50
Two lull size loudspeakers 131 x 10 x 31in. Player unit 250-0-250 80 mA. 6-3V 3.5A EI3V IA or 5V 2A .. 14.00 LOUDSPEAKERS P.M. 3 OHMS. 7 x 4in £1.25; Stin 0140;
clips to loudspeakers making it extremely compact, 350-0-350 80 mA 8.3V 3.5A, 8.3V IA or 5V 2A . 05.00. 8 x Sin £1.80; Sin 11.75; 10 x Sin £1.90; 10in £2.50
overall size only 131 x 10 x 8 )in., 3 watts per channel, plays 300-0-300V 120mA, 0.3V 4A C.T.; 13.3V 2A 16.00 RICHARD ALLAN TWIN CONE LOUDSPEAKERS. 8in
all records 33 r.p.m., 45 r.p.m. Separate volume and tone MINIATURE 200V 20mA, 8.3V lA 2f x 2t x Sin.... 75p diameter 4W £2.50, 10 in diameter 5W £2.95; Post 25p.
controls. MIDGET 220V 45mA, 13.3V 2A 21 x 21 x lin 90p Olin diameter, 6W, £3.50; 3 or 8 or 15 ohm models.
240V AC HEATER TRANS. 13.3V 1 amp 135p, 3 amp 01.209 SPEAKER COVERING MATERIALS. Samples Large S.A.E.
Mains. GENERAL PURPOSE LOW VOLTAGE. Tapped outputs Horn Tweeter. 2-16Kcis. SW 8 Ohm or 15 ohm 1220.
at 2 amp. 3, 4, 5. 8, 8, 9, 10, 12, 15, 18, 24 and 30V £4.00 De Luxe Horn Tweeters 2-18Kc/a, 15W, 15 ohm £4.00.
1 amp, 8. 8. 10, 12, 18, 18, 20, 24, 30, 36, 40, 48, 60 £4.00 TWO-WAY 3,000 c.p.s. CROSSOVERS I. 8 or 15 ohm 01'25.
amp, 6, 8, 10, 12, 18, 18, 20, 24, 30, 38, 40, 48, 80 08.00
5 amp, 8.8, 10, 12, 18, 18, 20, 24, 30, 38, 40, 98. 130 19.75 CASSETTE MACHINE MOTOR. 8 Volt.
12, 36, 48V 2 amp. £2.20; 20V 3 amp £2. 3, 5, 8, 10, 13 Will replace many types 01(26.
or 5-0-5V 5 amp. 0160; 0-0-6V 500mA 90p; 9V 1 amp
95p: 12V 300mA 75p; 12V 500mA 85p; 12V 750mA 95p.
AUTO TRANSFORMERS. 115V to 230V or 230V to 115V R.C.S. 3 WAY CROSSOVER
Bargain Price 150W 14.00; 500W 2760; 750W £15; 1000W £18. Complete with 12 ft. twin lead fitted with din speaker plug.
Attractive CHARGER TRANSFORMERS. Input 200/250V. Ready assembled with leads for speakers, bass, mid and
Teak finish £25 for 8 or I2V. 11 amp 1200; 2 amp 0250; 4 amp £4.00 tweeter. Crossover frequencies -950 cps and LI.95
Weight 13 lb. 85p Carriage BATTERY CHARGERS. Ready built with leads and clips 3,000 cps.
14 amp 22; 4 amp £4; 5 amp. £4.50.
FULL WAVE BRIDGE CHARGER RECTIFIERS:
SPECIAL OFFER! 8 or 12V outputs. ll amp 40p; 2 amp 55p; 4 amp 859
VALVE OUTPUT TRANSFORMER 50p.
MIKE TRANSFORMER MU metal 100-1 0145.
PUSH-PULL VALVE OUTPUT TRANSFORMERS.
SMITH'S CLOCKWORK MAINS ISOLATING TRANSFORMER 50 watt £12.50 100 watt 215.00
15 AMP TIME SWITCH Primary 0-110-240V. Secondary 0-240V 3 amps 720
0 TO 60 MINUTES
watts. Insulated terminals. Varnish impregnated. Fully
enclosed in steel case with fixing feet. Carr.
ELECTRO MAGNETIC
Single pole two-way Surface mounting Famous make (Value £19) OUR PRICE £ 12 95p PENDULUM MECHANISM
with fixing screws. Will replace existing Can be used as 800 watt auto transformers 240-110V.
1 5V d.c. operation over 200 hours continuous on SP2
wall switch to give light for return home, battery, fully adjustable swing and speed. Ideal displays,
garage, automatic anti -burglar lights. etc. Variable knob.
Turn on or off at full or intermediate settings. Fully
SET OF 3 MOTORS FOR teaching electro magnetism or for metronome, 95 Post
insulated. Makers' last list price £4.50. Brand new and fully
guaranteed.
COLLARO STUDIO strobe, etc.

OUR PRICE £ I 95 Post 259 115 VOLT TAPE DECK R.C.S. RECORD PLAYER AMPLIFIER
2 stage triode pentode valve. 3 watts output. Volume on/off
BLANK ALUMINIUM CHASSIS. 18 s.w.g. 2Iin sides L I 50 Post 50p and tone controls. Printed circuit L450 Post
6 x 4in 45p; 8 x 8in 53p: 10 x 7in 65p; 12 x Sin 85p; A.C. mains complete and tested.
14 x 9in 90p; 16 x Bin 90p; 12 x 3in 50p; 18 x 10in £1. VOLUME CONTROLS 80 Ohm Coax Sp yd. Complete with speaker.
ALUMINIUM BOXES 3 x 3 x 3in 809; 4 x 4 x 4in 70p; Long spindles. Midget Size
6 x 4 x 4in 80p; 9 x 4 x 4in £1; 12 x 4 x 4in £1 30. BRITISH AERIALITE COAXIAL PLUG 10p. PANEL SOCKETS 10p. LINE 18
ALUMINIUM PANELS 18 S.W.g. 6 x 4in 12p: 8x 8in 19p: 5 K. ohms to 2 Meg. LOG or AERAXIAL-AIR SPACED
LIN. L/S 20p. D.P. 359. 40 yd £2.00; 80 yd 13.00. OUTLET BOXES, SURFACE MOUNTING 25p.
4 x 3in 20y: 10 x 7in 24p; 12 x Sin 25p; 12 x Sin 34p: STEREO L/S 55p. D.P. 759. FRINGE LOW LOSSIA per BALANCED TWIN RIBBON FEEDER 300 ohms. 7p yd.
8 x Sin 34p; 14 x 9in 40p: 12 x Olin 47p; 18 x 10in 80p. JACK SOCKET Std. open -circuit 14p. closed circuit 28p;
PAXOLIN PANEL 10 x 8in 309. Edge 5K. S.P.Transistor 259. Ideal 625 and colour. P yd Chrome Lead Socket 45p. Phono Plugs 7p. Phono Socket 7p
1 inch DIAMETER WAVECHANGE SWITCHES, 45p ea. Wire Wound controls ltin diam. 3 Watts. 10 ohms to 100K JACK PLUGS Std. Chrome 20p; 3.5mm Chrome 15p DIN
2 p. 2 -way, or 2 p. 6 -way, or 3 p. 4 -way. British Made with long spindles tin dia. 85p each. SOCKETS Chassis 3 -pin 10p; 5 -pin 10p DIN SOCKETS
p.1. 2 -way, or 4 p. 2 -way, or 4 P. 3 -way. DUAL CONCENTRIC POT 500K LOG AND 500K LIN D.P. Lead 3 -pin 18p: 5 -pin 25p. DIN PLUGS 3 -pin 25p; 5 -pin 259.
TOGGLE SWITCHES, sp. 20p; dp. 25p; dp. dt. 30p. switch. Inner spindle 3 tin ; outer spindle 2tin 75p. VALVE HOLDERS bp; CERAMIC 10p; CANS bp.

BRITISH FM/VHF TUNING HEART ALL PRICES INCLUDE VAT 20p MINIMUM POST AND PACKING CALLERS WELCOME
88 to 108 Mc a British made. 2 Transistors ready aligned

RADIO COMPONENT
requires 10.7 Mc(s 1.F. Complete with tuning gang.
Connections supplied but some technical experience
essential.Our price L3.95 Poet 20P
SUITABLE I.F. STRIP £4.95. DECODER 14.95
Illustrated Brochure, Radio Books & Component Lists 10p Written guarantee.
20 Practical Electronics January 1975
 ALL OUR PRICES INCLUDE V.A.T.
WOOFER AND BAKER 141-F1 SPEAKERS
E.M.I. TWEETER KIT BAKER MAJOR 12" £8.50 HIGH QUALITY -BRITISH MADE
Pont
L575 (11,11:btl", 30-14,500 cis, 12in. double
REGENT
Woofer 24.25: Tweeter cone, woofer and tweeter cone
11.90) together with a BAKER
Comprising a fine example of a Woofer ceramic magnet assembly I2in. IS watts
101 x Olin with a massive Ceramic having a ffux density of
Magnet, 44oz Gauss 13,000 lines. 19,000 gauss and a total flux An inexpensive unit for the
Aluminium Cone centre to improve of 195,000 Maxwells. Bass beginner in high fidelity and
middle and top response. Also the E.M.I. resonance 90 c/s Rated 20 for general purposes. May be
Tweeter 31in square has a special watts. NOTE: 3 or 8 or used to improve any Radio,
lightweight paper cone and magnet flux 15 ohms must be stated. Amplifier, Hi-Fi or Television
10,000 lines. Crossover condenser and receiver.
full instructions supplied. Bass Resonance 45cps
Impedance Standard 8 ohms Module kit, 30-17,000 cis Flux Density 12,000 gauss
Maximum power 12 watts with tweeter, crossover, bale Useful response 45-13,000cps
and instructions. 3 or 8 or 15 ohm models.
Useful Response 35 to 18,000 cps E10.95
Bass Resonance 45 cps
SUITABLE ENCLOSURE 20 x 13 x Sin.
MODERN DESIGN. TEAK WOOD FINISH.
L10.50
Post 75p
BAKER
Please state 3 or 8 or 15 ohms.
L7/5
ANOTHER R.C.S. BARGAIN ! "BIG SOUND"
ELAC 9 Sin. HI-FI SPEAKER TYPE 59RM DE -LUXE Mk II
This famous unit now available. 10 watts, 8 ohm. SPEAKERS I2in. IS watts
Price L295 Robustly constructed to stand up to
Especially designed to provide
long periods of electronic full range reproduction at an
power. economical cost. Suitable for
As used by leading groups.
8" or 10" x 6" ELAC Uselul response 30-13,000 cps.
use with any high fidelity
Bass Resonance 55 cps. system. Built-in concentric
HI-FI SPEAKER tweeter cone.
Bass Resonance 30cps
Dual cone plasticised roll sur- GROUP "25" Flux Density 14,000 gauss
round. Large ceramic magnet. 12in 25 watt Useful response 25-18,000cps
50-18,000 cps. Bass resonance 3, 8 or 15 ohms. 8 or 15 ohms models.
55 cps. 8 ohm impedance.
10in round E450.
10 watts.
L3.75 GROUP "35" L9.75
TEAK VENEER HI-FI SPEAKER CABINETS
I2in 35 watt
3, 8 or 15 ohms.
E8.50
Fluted Wood Fronts SUPERB
MODEL "A". 20 x 13 x gin GROUP "50"
0.cn Post
For 12 in. dia. or 15in. 50 watt L17.80 I2in. 20 watts
10in speaker. .. 75p 8 or 15 ohms. A high quality loudspeaker,
MODEL "B". 18 x 10 x Sin 50 watt I2in VERSION E12.95 its remarkable low cone
For 13 x Sin. or Post, resonance ensures clear
8 in. speaker L660 reproduction of the deepest
MODEL "B" 2 ditto. Triangular MAJOR 100 WATT bass. Fitted with a special
Corner Version. ALL PURPOSE copper drive and concentric
tweeter cone resulting in full
MODEL "C". 16 x 8 X Sin. TRANSISTOR range reproduction with
For 8 x Sin. itpoc Post remarkable efficiency in the
speaker ' 35p AMPLIFIER
All purpose transistorised.
upper register.
Bass Resonance 25cps
LOUDSPEAKER CABINET Ideal for Groups, Disco and P.A.
WADDING 18in wide, 20p ft. Flux Density 18.500 gauss
4 inputs speech and music. 4 way Uselul response 20-17,000cps
mixing. Output 8/15 ohm a.c. Mains. Carr. 8 or 15 ohms models.
DECCA DOME TWEETER Separate treble and bass controls.
Guaranteed. Details S.A.E.
£49 £1.00
3;In. diem. 18,000 C.P.S. 25 WATTS 8 it £3.30
NEW MODEL MAJOR 50 WATT L13.80
BARGAIN 4 CHANNEL 4 inputs, 2 way mixing, 239.95. Carr. £1. Ideal disco amp.
TRANSISTOR MONO
MIXER. Add musical CALLERS ONLY! DE -LUXE 100 WATT AMPLIFIER
highlights and sound effects CHASSIS. 7 Valve version, 4 inputs. 10 wide range AUDITORIUM
to recordings. Will mix controls. For Mikes, Discos, Organs, Guitars, etc.
Microphone, records, tape
and tuner with separate
4, 8 and 15 ohm Loudspeaker matching. £69 I2in. 25 watts
controls into single output. A full range reproducer for
9 volt battery QUALITY LOUDSPEAKER ENCLOSURE high power, Electric Guitars,
operated. E450 Teak veneered Sin thick wood cabinet. Size public address, multi -speaker
STEREO VERSION OF ABOVE 25.95. 18.1in x 113iin x Olin. Weight 231bs. This systems, electric organs,
BARGAIN 3 WATT AMPLIFIER. 4 Transistor cabinet features a wide mesh Silver Grill Ideal for Hi-Fi and Disco-
Push -Pull Ready built with volume, treble and covering a separate compartment for mount- theques.
bass controls. 18 volt battery operated. L450 ing Tweeters or Mid -Range Horn. The fully
sealed bass compartment is cut out for
Bass Resonance
Flux Density
35cps
15,000 gauss
81in Woofer. £7.50. Carr. 85p. Useful response 25-18,000cps
THE "INSTANT" BULK TAPE Rosewood Version 28'50. Carr. 85p. 8 or 15 ohms models.
ERASER do HEAD DEMAGNETISER.
Suitable for cassettes, and all sizes of
tape reels. A.C. mains 200/250V.
Leaflet S.A.E. £3.7c Post
20p
SPECIAL OFFER 95p.
100 Ohm 20 watt Rheostat 23in dia. Ceramic Former.
Screw Terminals tin. dia. spindle.
Post 25p.
L12.95
WAFER
THIN HEATING ELEMENTS 20 Watt 100 ohm Rheostat 2;in dia. Ceramic former screw
terminals fin dia. spindle. 95p. Post 25p. AUDITORIUM
OFFERING 1001 USES for every type of heating and
drying applications in the home, garage, greenhouse
factory (available in manufacturing quantities). APPros R.C.S. STEREO DECODER ISin 35 watts
size 10; x 81 x in. Operating voltage 200/250V. a.c. British made. Ready aligned and tested. Complete A high wattage loudspeaker
250 watts approx. Printed circuit element enclosed in with instructions. Size 3in x 2in. L4-95 of exceptional quality with a
asbestos fitted with connecting wires. Completely flexible level response to above
providing safe Black heat. British -made for use in photo- 8,000 cps. Ideal for Public
copiers and print drying equipment.
Ideal for home handymen and experimenters. Suitable
WEYRAD COILS Address, Discotheques. Elec-
tronic instruments and the
P50 2CC 40p RA2W 85p
for Heating Pads, Food Warmers, Convector Heaters. etc. P50,1AC 130p OPT1 65p home.
Must be clamped between two sheets of metal or asbestos, P50'3CC 40p LFDT4 85p Bass Resonance 35ePe
etc., to make efficient clothes dryers, towel rails -ideal for PCA1 85p Twin gang £1.10 Flux Density 15,000 gauss
airing cupboards. Ideal for anti -frost device for the garage Useful response 20-14,000cps
- -preventing frozen radiators or acting as oil sump heater. 8 or 15 ohms models.
Use in greenhouse for seed raising and plant protection. DELUXE 4 POLE MOTOR
Invaluable aid for bird houses, incubators, etc., etc. Can
be used in series for lower heat. Or in parallel for higher
heat applications.
h. 1,400 r.p.m. reversible 92 Watt,
spindle 11in x 7/32in, size 31in x
3in. As illustrated. 240V a.c. mains.
£2.25
Post 25p
L17.80
E.M.I. GRAM MOTOR
ONLY 40p EACH (FOUR FOR CI50) 120V or 240V a.c. 2,400 rpm. 2 -pole Hi-Fi Enclosure Manual containing Plans, designs,
70mA. Size 2; x 21 x 2tin. E1.00 crossover data and cubic tables. 63p.
ALL POST PAID -Discounts for quantity. Post 25p

CUSTOMERS FREE CAR PARK OPEN 9-6 p.m. WEDNESDAYS 9-I p.m., SATURDAYS 9-5 p.m. (Closed for Lunch 1.15-2.30)

SPECIALISTS
(Export: Remit cash and extra postage.)
337 WHITEHORSE ROAD
Buses 50, 68, 159. Rail Selhurst
CROYDON
Telephone 01-684-1665
Practical Electronics January 1975 21
 DISCO) SHOP, SOUND TO LIGHT, STAGE
PHOTON FLOOD LIGHT FITTINGS
TYPE B 3 -BANK UNIT
Has two brackets to accept P C Board. Transformers. Also has holes
in ends for Potentiometers. Jack Socket. Cable. etc. Ideal for making
Sound to Light and Strobes. Base Cover included. Less Lamps. only
£6.50
inc VAT. P. & P. 40p
SOUND TO LIGHT
Three channel. using Type B unit. Ideal for small disco's and home--7,
entertainment. Complete with Lamps. Ready wired,
£25
inc. VAT. P. & P. 40p
STROBE UNIT 74

Using Type B unit. Adjustable frequency. Single knob control. Com-

plete with Lamps. just plug into mains-that's it.
£25 TYPE A
complete. inc VAT P. & P. 40p.
100 WATT SPOT LAMPS
Red. Pink. Green. Yellow, Blue, Violet. Clear Only ONLY
80p
each Minimum 3 Lamps f2.40 inc VAT. P & P 25p
rlnc VAT
50
Less Lamp

TRAFALGAR SUPPLIES .:TP P s°

Dept H.T. Standish Street Burnley Lancs

ENGINEERS
10 WATTS PER CHANNEL RMS
STEREO AMPLIFIER
This 76 pege at less than 01% distortion. Max. RMS output in excess
FREE book of 15 watts per channel.
shows how! " 4-16 ohm Load * 40 dB NFB
YOURSELF 15-50 kHz (-IdB) 150 mV input

F ailB RAWITH MORE PAY!

Do you want promotion. a better job. This helpful guide to success should be
higher pay' "New Opportunities" shows read by every ambitious engineer.
you how to get them through a low-cost Send for this helpful 76 page FREE book strosermil POWs.
home study course. There are no books to now. No obligation and nobdy will call on
buy and you can pay -as -you -learn. you. It could be the best thing you ever did. ./ kite

NI SM 'SCUT OUT THIS COUPON MI NM IIIII a

POi,PO/,,SCHOOSE A BRAND NEW FUTURE HERE!
Nok'
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Tick or state subject of Interest. Post to the address below.

C. dr G. Radio. TV 0 C. & G. LI Installa -

Completely assembled PCB using top grade components
Electronics. Mechanics dons and Wiring (plus backplate/heatsink) including balance volume and
Practical Radio and Radio Amateurs 0 General Electrical 0 tone controls plus mono -stereo switch. Operates from
Electronics (Tech- 0 Engineering
natron)
Practical TV
Society of Engineers 22-24V d.c. Board also includes a single 2 -stage mic. or
Colour Television 0 Engineer- guitar pickup preamp. (2 BC149). Instructions are
Electronic Engineer- O (Electrical
Computer Electronics
ing
C. & G. LI Radio TV 0
1:1
ing) included for a simple mod. to adapt this for stereo
Television Mainten- Electrical Installations 0
ance and Servicing Servicing cert. and Wiring operation giving 150mV at IM ohm sensitivity. Full
General Radio and CI Post Master General 0 C. & G. Electrical 0 circuit supplied.
TV Engineering 1st & 2nd class certs. Technicians (Primary)
Radio Servicing. Main- O L. dt G. Electrical CI C. & G.
mumcations
Telecom- 0 FANTASTIC AND UNREPEATABLE BARGAIN.
Engineering Practise
tenance and Repairs
L990 plus 60p P. & P., inc. VAT. Power supply corn-
To ALDERMASTON COLLEGE ponents to operate from the mains available, add £2.90
Dept. EPE 01, Reading RG7 4P F inc. VAT.
NAME (Block Capital. Rime)
ADDRESS
COL,
Ape
EDRICK ELECTRONICS LTD.
Other suthects
Accredited by CACC /Aerator OS A El CC (DEPT. P6)
BRITISH INSTITUTE OF ENGINEERING TECHNOLOGY 164 HIGH STREET, BARNET, HERTS.
22 Practical Electronics January 1975
 Everything you need is in our

/Marshall
New Catalogue
available now price 20p
(100 pages of prices and data)

Call in and see us 9-5.30 Mon -Fri

A Marshall (London) Ltd. Dept. PE
42 Cncklewood Broadway London NW2 3DH Telephone 01-452 0161 2 Telex 21492 9-5.00 Sat
85 West Regent Street Glasgow G2 200 Telephone 041-332 4133 Trade and export enquiries welcome

Popular Semiconductors BD135 0.43 BFY19 0,62 MJE2955 PW TELETENNIS KIT

2N456 0.80 2N2907 0.22 2N4061 0.11 AD150 0.83 BC171 0.13 80136 0.49 BFY20 0.50 1.12 As featured on BBC Ntionerld and in the
2N456A 0,85 2N2907A 0.24 2N4062 0.11 ADI61 0.45 BC172 0.11 BD137 0.55 BFY29 0.40 MJE3054 Daily Mail 2 Oct 74 Ideal prime for Whole
BD138 0.63 BFY50 0.23 family No need to modify your TV set, lust
2N457A 1,20 2N2924 0.14 2N4126 0.20 AD162 0.45 8C182 0.12 0.88 plug In. to serial eockt
2N490 3.16 2N2925 0.17 2N4289 0.34 A01611 PR BY182L 0.12 B0139 0.71 BFY51 0,23 MP8111 0.32 Parts Ilea es follow. A Resistor Pack LI
2N491 3.59 2N2926 2N4919 0.114 AD162 1-05 BC183 0.09 BD140 0,87 BFY52 0.21 MP8112 0.40 P 6 P 20p B Potentiometer Pack L1.21
2N492 Green 0.12 2N4920 0.99 0.40 BC183L 0.09 BDY20 1.05 BFY53 0,19 MP8113 0.47 P P 20p. C Capacitor Pack [3.1 P. 6 P.
3.99 AF109R 200 D Semiconductor Peck [WM P P.
2N493 4,20 Yellow 0.11 2N4921 0.73 AF115 0.24 BC184 0.11 BF115 0.25 BFY90 0.75 MPF102 0.39 ?Op E IC Socket. LIP. A P 20p. F Trana-
214696 0.22 Orange0.11 2N4922 0.84 AF116 0.25 BC184L 0.11 BF116 0.23 BRY39 0.23 MPSA05 0.25 formur tl II P. 8 P 25p. (3 PCB s L730
2N697 0.18 2N3043 0.25 2N4923 0.83 AF117 0.20 BC186 0.25 BF117 0.43 BU104 2.00 MPSA06 0.28 P P 20p H Swrtches 14.50 P.. P 200.

2N698 2N3054 0.12 0.55 BC187 0.27 BF119 0.58 BU105 2.25 MPSA55 0.28 UHF Modular cut EV 50 P 6 P 20p
0.40 0,60 2N5172 AF118 Special Prices -complete kit 4moluding
2N699 0,45 2N3055 0.75 2N5174 0.22 AF124 0.30 BC207 0.12 BF121 0,25 C106A 0.48 MPSA56 0.27 c D12 P. 6 P 500 Sections A -F Incl.
2N706 0.14 2N3390 0.28 2N5175 0.26 AF125 0.30 BC208 0.11 BF123 0.27 C106B 0.55 NE555V 0.70 E23.50 P P 30p Assembly intructions
2N706A 0.18 2N3391 0.23 2N5176 0.32 AF126 0.28 BC212K 0.10 BFI25 0.25 C106D 0.85 NE560 4,48 With complete kit or 750 on '1.01.1
2N708 0.17 2N3391A 0.29 2N5190 0.92 AF127 0.211 BC212L 0.16 BF152 0.20 C106E 0,43 NE561 4.80
2N709 0.42 2N3392 0.13 2N5191 0.95 AF139 0.39 BC214L 0.16 BF153 0.21 CA3020A 1.30 NE565A 4.48
2N711 0.50 2N3393 0.13 2N5192 1.24 AF170 0.25 BC237 0.09 BF154 0.20 CA3046 0,70 0C23 1,35
2N718 0,23 2N3394 0.13 2N5195 AF172 0.25 BC238 0.09 BF158 0,23 CA3048 2.11 0C28 0.76
2N718A 0.28 2N3402 0.18 2N5245 0.43 AF178 0.55 BC239 0.09 BF159 0.27 CA3089E 1.96 0C35 0-60 P.C. Marker Pen Delo 33PC
2N3403 0.19 0.49 0.65 BC251 0.20 BF160 0,23 CA3090Q 4.23 0C42 0.50
2N720 0,50 2N5457 AF179
BC252 BF161 CD4000 Price Sip
2N721 0.55 2N3440 0.59 2N5458 0.45 AF180 0.58 0.18 0.42 0-51 0C45 0.32 Zeners 400MW 2 7V -43y 11p. 1W 3.3V -120V
2N914 0,22 2N3441 0.97 2N5459 0.41 AF186 0.413 BC253 0.23 BF163 0.32 CD4001 0.51 0071 0.20 17p.
2N916 0,29 2N3442 1.25 40361 0.48 AF200 0.35 BC257 0.09 BF166 0,32 CD4002 0,51 0072 0.25 IC Sockets 8 DIL I6p. 14 OIL 178.16 OIL 20p.
2N918 2N3414 0-20 40362 0.50 AF239 0.51 BC258 0.09 BFI67 0.21 CD4009 1.07 0081 0.25
2N929
0.32
2N3415 0.21 40363 0.88 0.72 BC259 0.13 BF173 0-24 CD4010 1,07 0083 0.24
Liquid Crystals -E13
0.30 AF240 En -stock S A E for details of CMOS battery
2N1302 2N3416 0.34 40389 0.48 AF279 0.54 BC261 0.20 8F177 0.21 CD4011 0.51 ORP12 0.55
0.111
0.18 BF178 CD4015 248 operated clock kit using LCD's.
2N1303 0.19 2N3417 0.24 40394 0.56 AF280 0.54 BC262 0.35 R53 1.20
2N1304 0,24 2N3638 0.15 40395 0.85 AL102 0.75 BC263 0.23 BF179 0.43 CD4016 1.02 RL54 0.15
Scorpio Car ignition Kit -£11.50+
2N1305 0.24 2N3638A 0.15 40406 0.44 AL103 0.70 BC300 0-36 BFI80 0.35 CD4017 2,86 SC35D 1.68 VAT
2N1306 0.31 2N3639 0.27 40407 0.33 BC107 0.18 BC301 0.34 BF181 0.34 CD4020 2.96 SC36D 1,46 IMF44OV (1-10.
2N1307 0.22 2N3641 0-17 40498 0.50 BC108 0.15 BC302 0.29 BF182 0,40 CD4023 0.51 SC40D 1-89 BSTB0246 21.05. Transformer E2.75.
2N1308 0.40 2N3702 0.12 40409 0.52 BC109 0.19 BC303 0.54 BF183 0.40 CD4024 1.90 SC41D 1.32 Minitron E1 -S5.
2N1309 2N3703 0.13 40410 0.52 0.15 BC307 0.11 BF184 0.30 D4027 1.58 SC45D 1.89 DL707 (2.35 or 4 for
0,36 BC113
2N1671 1.44 2N3704 0.14 40411 2.00 BC115 0.17 BC307A 0.10 BF185 0 30 CD4028 2.34 SC45D 1.96
2N1671A 1.54 2N3705 0.12 40414 3.55 BC1I6 0.17 BC308 0.12 BF194 0,12 CD4029 3.79 SC5OD 2,60
2N1671B 1,72 2N3706 0.09 40430 0.85 BC116A 0.18 BC308A 0.12 BF195 0,12 CD4041 2.11 SC51D 2-39
BF196 0.13 CD4044
2N1671C 4.32
2N1711
2N3707 0.13 40583 0.23 BC117
0.87 BC118
0-21 BC3088 0.09
0.10 BF197 0.15 CD4047
2.11 SL414A
SL623
1,80
4-59
Resistors Tant Beads
0.45 2N3708 0.10 40601 0-11 BC309 1,65
2N1907 5,50 2N3709 0.11 40602 0.48 BC119 049 BC309A 0.10 BF198 0.18 04049 0.90 TAA263 1.00 W Tol Price Value Price
2N2102 0,50 2N3710 0.12 40603 0.53 BC121 0.23 BC309B 0.10 BF199 0.19 CD4050 0-90 TAA350 2.10
2N2147 0.79 2N3711 0.11 40604 0.56 BC125 0.16 BC237 0.21 BF200 0,40 LM301A 0.48 TAA621 2.03 5% 1p 0,135 14p
2N2148 2N3712 0.98 40636 1-10 BC238 0.19 BF225.1 0,19 LM304A 2.03 TAA6618 9
2N2160 0.90 2N3713 1.20 40669 1.00 BC132 0.30 BC337 0.11 8F237 0,22 LM309K 1.96 1.32
2N2192 0.70 BC134 BF238 0.22 LM702C TAD100 1.50 5% 2p 0.47'35 14p
0.40 2N3714 1.33 40673 0.13 BC338 0.19 0.75
2N2192A 0.40 2N3715 1.50 AC107 0.51 BC135 0.13 BCY30 0.64 BF244 0.21 LM709 Filter 0.70 1 10% 23p 22/35 14p
2N2193 2N3716 1.80 AC113 0.18 BC136 0.17 BCY31 0,64 BF245 0,33 TO99 0.48 TBA271 0.64
0.58
BF246 8IDIL
2 10% 6p 4 7.35 180
2N2193A 0.81 2N3771 2.20 AC117 0.20 BC137 0.17 BCY32 1.15 0.511 0.38 TBA641B
2N2194 0.73 2N3772 1.10 AC126 0.20 BC138 0.24 BCY33 0,45 BF247 0.49 14DIL 0-40 2.25 29 5% 7p 10;16V lip
2N2194A 0.30 2N3773 2.85 AC127 0-20 BC140 0.34 BCY34 0,49 BF254 6,16 LM723C 0.90 TBA800 1.50 5% 9p 47/6 3V 20p
2N2218A 0.22 2N3789 2.08 AC128 0.20 BC14I 0.29 BCY38 0,55 BF255 0.17 LM741 TBA810 1.50
TO99 10 5% 10p 100/3V 200
2N2219 0,24 2N3790 2.40 AC151V 0.25 BC142 0.23 BCY39 1.50 BF257 0,44 0.40 TIL209 0.30
2N22I9A 026 2N3791 2.35 AC152V 0.17 BC143 0.25 BCY40 0.67 BF258 0.59 BOIL 0.40 TIP29A 0.49
2N2220 0.25 2N3792 2.69 AC153 0.25 BC145 0.21 BCY42 0.28 BF259 0.55 14011 0.39 TIP30A 0.58
2N2221 0.19 2N3794 0.24 AC153K 0.33 BC147 0.12 BCY58 0.21 BFS21A 2.30 LM747 1,00 TIP31A 0.82
2N2221A 0.37 AC154 0.20 BC148 0.22 BFS28 0.92 LM748 TIP32A 0.74
2N2222
0.21
0-20
2N3819
2N3820 0.134 AC176 0.23 BC149
0.13
0.12
BCY59
BCY70 0.17 BFS61 0.27 1301L 0,60 TIP33A 1.01 Veroboard
2N222A 0.25 2N3823 0.78 AC176K 0.33 BC153 0.16 BCY71 0.22 BFS98 0-25 140IL 0.73 TIP34A 1.51 Copper Plain
2N2368 0-25 2N3900 0.28 AC187K 0.23 BC154 0.18 BCY72 0,13 BFX29 0.30 LM7805 2.00 TIP35A 2.09 0 1 0 15 0.1 0,15
2N2369 0.37 2N3901 0.32 AC188K 0.34 80157 0.14 BCY87 3.54 BFX30 0.27 MC1303P TIP36A 3-70 2-5 x 31In 280 20p - 14p
2N2369
2N2646
0.41 2N3903 0.24 ACY18
ACY19
0.24 BC158
0-27 BC159
0.13 BCY88 2.42 BFX44
BFX63
0.33
2,48
1.21 TIP41A
MC1310 2.92 TIP42A
0.79
0.90
25x 5in 30p 30p - 14p
0.55 2N3904 0.27 0.14 BCY89 0,97 39 31 -in 30p 30p
2N2647 0.24 ACY20 0.22 BC160 BFX68 0.30 MC1458CP1 TIP2955 0.93
2N2904
1.12 2N3905
0.28 BC167B
0.37 1313115 0,75
BFX84 0,24 0.79 TIP3055 0.60 39 5in 34p 35p - - 24p
0,22 2N3906 0.27 ACY21 0-13 B0116 1.00
39 17in E1-21 95p 76p 69p
2N29044 0.24 2N4036 0.63 ACY28 0.20 BC168B 0.13 B0121 0.75 BFX85 0.30 MJ480 0.90 ZTX300 0-13
2N2905 0.24 2N4037 0.42 ACY30 0.58 BC168C 0.11 BD123 0.32 BFX87 0,28 MJ481 1.14 ZTX302 0.20 Pins 24p 24p
36
2N2905A 0.26 2N4058 0.113 AD142 0.59 BC1698 0.13 BD124 0,67 BFX88 0.25 MJ490 0.98 ZTX500 0,15
BFX89 1.38 200 89p 92p
2N2906 0.19 2N4059 0.09 AD143 0.60 BC169C 0.13 BD131 0-40 0.45 MJ491 ZTX502 0,18
2N2906A 0.21 2N4060 0.11 I AD149V 0.58
I BC170A 0,11 BD132 0 50 BFY18 0.52 MJE340 0.45 ZTX530 0,21 Trade and Retail supplied.

Integrated Circuits-TTL Reductions! Potentiometers

SN7480 0.75 SN7495 0.90 SN74151 1.10 SN74175 1.29
1.00 SN74153 1.09 SN74176 1.44
Linear or Log Single Double
SN7400 0.113 SN7409 0.33 SN7430 SN7450 SN7496
-
0.16 0.16 SN74131 1.25
0.16 SN7410 SN7432 0.45 SN7451 SN7482 047 SN74100 2.16 SN74154 1-84 SN64180 1.44 Rotary Pots 111p 45p
SN7401 0.18 0.16
SN7401AN SN74II 0.25 SN7437 0.35 SN7453 0,16 SN7483 1.20 SN74107 0.43 SN74155 1.55 SN74181 5.16 Rotary Switched 28p
0-33 SN7412 0.21 SN7438 0.35 SN7454 0.16 SN7484 0.95 SN74118 1.00 SN74157 1-09 SN74190 1.95 Sliders 50p tlOp

SN7402 0.16 SN7413 0.50 SN7440 0.18 SN7460 0.16 SN7485 1.58 SN74119 1.92 SN74160
SN74161
1.51
1.58
SN74191 1.95 Full range of capacitors
SN7403 0.18 SN7416 0,45 SN7441 0,65 SN7470 0,30 SN7486 0.45 SN74121 0.57 SN74192 2.05
stocked. See catalogue for
SN7404 0.24 SN7417 0,30 SN7442 0,85 SN7472 0.31 SN7490 0.65 SN74122 0.90 SN74182 1.51 SN74193 2.30
SN7405 0.24 SN7420 11.16 SN7445 1.59 SN7473 0.44 SN7491 1.10 SN74123 0.72 SN74164 2.01 SN74198 1-58 details
SN7406 0.45 SN7423 0,32 SN7446 2,00 SN7474 048 SN7492 0.75 SN74141 1.00 SN74165 2.01 SN71197 1.58 Presets -Horizontal or Vertical
SN7407 0.45 SN7425 0.31 SN7447 1.30 SN7475 0,59 SN7493 0 65 SN74145 1-44 SN74167 4.10 SN74198 3.16
SN7406 0.25 SN7427 0,45 SN7448 1.50 SN7476 0,45 SN7494 0,95 SN74150 1.44 SN74I74 1.80 SN74100 2,88 0.1W 69 0.2W 6p 0 3W Op

Diodes and Rectifiers OPTO & LED's Bridge Rectifiers Construction Kits
PIV 50 100 200 400 600 800 1000 Red, green and yellow Plastic 1A 2A 4A 6A AV7 Aerial Amps E2.04
1,5 15p 17p 20p 22p 25p 27p 30p 0.16 diameter 31p 50 0.24 0.32 0,60 0.62 UHS70 Transmitter £2.74
3
10
35 54p
-
15p17p
35p
92p
20p
40p
22p
47p
25p
56p - -
27p

1.18 2.15 2.52 3.85 4.20 Minitron E1.55

30p 0'20 diameter 33p
DL707 £2.35 or 4 for El
100
200
400
0.36
0.30
0.38
0-37
0.41
0.45
0.70
0.75
0,65
0.75
0.80
1.10
MUE7 Receiver for above
EW18 Electronics dice
E3.22
E6.53
Cathode Stud Only IN3766 135A 800pv) E3.65 IN3786 (35A 1000pv) 24.20 600 0.40 0.52 0,95 1,25 EX20 Electronic Dice +- Sensor E7.71
IN34A 10p BA102 25p BA145 17p BY237 12ip 0A47 OA90 7p SCR's 100V 200V 400V 600V
IN914 7p BAII0 25p BAI54 12p BY210 35p 0A70
Tip
Tip 0A91 7p fA 0.43 0.44 Mall Order
IN916 7p BA115 Tp BY100 15p BYZ11 32p 0A73 10p 0A95 7p 1A 0.45 0.50 0.60 VAT All pric exclusive P P 20p
AA119 Tp BA111 17p BY126 15p BYZ12 30p 0A79 0A200 7p 1 2A 0.38 0.42 0.53 0,75
AA129 15p BA142 17p BY127 17$p 0A9
7p
3A 0.47 0.53 0.10 0.90 OUR NEW GLASGOW SHOP IS
10p 0A81 Sp 0A202 19p
BA100 15P 0A141 12p BY140 21 0A10 20 0A85 10 0A210 27 4A 0.50 055 0,85 NOW OPEN

23
Practical Electronics January 1975
 -...,
PE SCORPIO Mkt
ignition system kit 4fin .< 3iin METER. 300.,

new from MULTIMETER Model C-7081

GN Range Doubler 50,000 ohm/
50/4A or 100/IA, 13-65. 11 p P. & P.

volt High Sensitivity Meter

MULTI.
ELECTRO SPARES E14.40.

TAPE
20p P. & P.
METER

*6 OR 12 VOLT monnwsis Model D62

RECORDER
*+ VE AND- VE GROUND CEVEL
20,000 ohm/
volt, 0.00.
METER
15p P. & P.
Here's the new, improved version of the original PE Scorpio 500mA, 70p. 5p P. & P.
Electronic Ignition System - with a big plus over all the other
kits - the PE Scorpio Kit is designed for both positive and
negative ground automotive electrical systems. Not just +ve CARDIOID .6
ground. Nor just -ye ground. But both! So if you change cars. DYNAMIC
you can be almost certain that you can change over your
PE Scorpio Mk. 2 as well.
Containing all the components you need, this Electro Spares
PE Scorpio Mk. 2 Kit is simply built, using our easy to follow
instructions. Each component is a branded unit by a reputable
7 MICROPHONE
Model UD-130.
quency
15,000c/s.
Fre-
response 50-
Impedance
001* . ...^2F7

3 WATT STEREO
,..,:,,,71

manufacturer and carries the manufacturer's guarantee. Ready Dual 50K and 600 ohms, AMPLIFIER
drilled for fast assembly. Quickly fitted to any car. 16.55. I ip P. & P. f430. lop P. & P.
When your PE Scorpio Mk. 2 Is Installed, you instantly benefit
from all these PE Scorpio Mk. 2 advantages: All above prices include 8% V.A.T. LARGE S.A.E. for List No. 10.
* Easier starting from cold * Firing even with wet or oiled -up Special prices for quantity quoted on request.
plugs * Smoother running at high speed * Fuel saving
* More power from your engine * Longer spark plug life
* No more contact -breaker burn. M. DZIUBAS
Electro Spares prices: 158 Bradshawgate Bolton Lancs. BL2 IBA
De luxe Kit only £11.50 inc. VAT and p & p.
Ready Made Unit £14.75 inc. VAT and p & p.
State 6V or 12V system.
Send SAE now for details and free list. CALCULATOR OFFER!
SINCLAIR TEXAS
FM VARICAP STEREO TUNER Cambridge £17.25 T11500 £26.25 BUY IT
Cam. Memory £24.00 T12000 £13.95 WITH
As featured in the May 1973 issue of 'Practical Electronics'.
Superb Hi-Fi tuner Kit now available from Electro Spares.
Executive C23.90 112550 £29.95 ACCESS.
Exec. Memory £28.45 TI3500 £35.00 etc.
Including cabinet and all components - pre-set Mullard Scientific £25.00 SR10 £31.85
modules for R.F. and I.F. circuits. Motorola I.C. Phase Lock
Loop Decoder for perfect stereo reception. No alignment
BC107 10p BC184L 10p TIP2955 85p IN914 Sp 7474 42p
needed. Guaranteed first time results - or send it back, and BC108 10p BC212L 12p TIP3055 90p IN916 Sp 7475 60p
we'll return it in perfect order (for a nominal handling charge). BC109 10p BC213L 12p TIS43 15p IN4148 Sp 7476 42p
Electro Spares price only £28.50 inc. VAT and p & p. BC177 22p BC214L 12p TIS74 50p 7400-5 20p 7483 £1 .25
BC178 22p BC182K 10p ZTX304 26p 7410 20p 7486 46p
BC179 24p BC183K 10p ZTX504 35p 7413 36p 7490 66p
80182 10p BC184K 10p 0A10 30p 7420 20p 7492 70p
BC183 10p BC212K 12p 0A47 7p 7430 20p 7493 66p
BC184 10p BC213K 12p 0A73 7440 20p 74107 45p
'GEMINI' STEREO AMPLIFIER BC212 12p BC214K 12p 0A81
Op
6p 7442 Up 74121 alp
BC213 12p TIP29A 52P 0A90 Op 7447 £1.30 74141 El - 00
A superb unit with a guaranteed output of 30 watts RMS per BC214 12p TIP30A 62P 0A91 Op 7470 34p 74151 £1 .00
channel into 8 ohms. Full power THD is a mere 0.02%, and BC182L 10p TIP41A 85p 0A200 Op 7472 34p CA3026 90p
BC183L 10p TIP42A 95p 0A202 9p 7473 45p CA3046 629
frequency response is -3 dB from 20 Hz to 100 kHz into 8 or
15 ohms. Electro Spares have already sold 100s and 100s of
these Kits. Get yours now I Depending on your choice of 702 14 pin OIL 45p 741 8 pin DIL 36p 2N3242 El .45 BFY52 22p
709 8 pin DIL 35p 741 TO -99 36p 2N3819 20P 0C24 50p
certain components, the price can vary from £50 to £60 inc. 709 TO -99 35p 748 8 pin DIL 36p 2N3820 45p 0C28 70p
VAT and p & p. 709 14 pin DIL 38p 747 14 pin DIL 90p 2N4442 800 0C29 75p
710 la pin DIL 39p SL301B ?Sp BCY70 14p 0C30 60p
* All components as specified by original authors, and sold 710 TO -99 36p 2N1302 12p BCY71 14p 0C35 60p
733 14 pin OIL 2N1304 13p BCY72 13P 0C44 20p
separately if you wish. E1.39 2N3053 16p BFY50 25p oc4s 20p
* Full constructional data book with specification graphs, 741 14 pin DIL 39p 2N3055 48p BFY51 21p 0076 20p
fault finding guides, etc. 55p plus 4p postage.
* Price List only. Please send S.A.E. (preferably 9 x 4 DIECAST BOXES: aiinx2i.inklin, 50p; 43,ink2kink2in, 60p; 7i. nx4finx2in, £1 .50.
RESISTORS: TRS 2% E24, 2ip; W.W. ON 10p, 6W 10p, 9W 12p, 12W 15p.
minimum) for full details. DAL° PEN: 77p.
DISC CERAMICS, all values 10p. TANTALUMS 13p. I.C. SOCKETS 8 pin 15p;
14 pm 15p; 16 pin 16p. SOLDER, 18 S.W.G. £l-80 per f kg 22 S.W.G. £1 .90 per
f kg
No LIta. PrIce too unstable. Phon for quote.

ELECTRO SPARES
MI' Muth eSI Iry C(mfrpotielit CelltIC in
VAT INCLUSIVE! POST FREE OVER £3!
49-51 ST. MARY'S ROAD, OATLANDS VILLAGE
288 ECCLESAIIRD.,SHEFFIELD Sll 8PE (D)
Tel: Sheffield I 0742 668888 P.E. C. TEL. WALTON 21324
C.W.O.
MaWIIE0YrdBeRrlDoGnEly,.SURREY. P. & P. 15p

24 Practical Electronics January 1975

 ,,,,,,_,..
STROBE! STROBE! STROBE!
VARIABLE VOLTAGE TRANSFORMERS
INPUT 230/240V a.e.50/60 OUTPUT
VARIABLE 0-260V All Types
Build a Strobe Unit, using the latest type Xenon
white light flash tube. Solid state timing and
uperior Quality Precision Made
NEW POWER RHEOSTATS t4 f7
_ iii4":44

triggering circuit. 230/250V a.c. operation. New ceramic construction, vitreous

SHROUDED TYPE EXPERIMENTERS' ECONOMY KIT enamel embedded winding, heavy
200 watt (I amp) MOO Speed adjustable to 30 flash per sec. All duty brush assembly, continuously
0.5 KVA (21 amp) (MAX) L1000 1

electronic components including Xenon Tube

I KVA (5 amp) (MAX) LI410 rated.
2 KVA (10 amp) (MAX) L28-10 and instructions [6.30. Post 30p. 15 WATT 10/25/50/100/150/500/Ik/ohm
3 KVA (15 amp) (MAX) L31.25 INDUSTRIAL KIT £1.15. Post 10p.
4 KVA (20 amp) (MAX) L72-50 Ideally suitable for schools, laboratories, etc. 50 WATT (/5/10/25/50/100/250/500 1.5k/
37.5 amp (MAX) 1 0 2 50 Speed adjustable 1-80 f.p.s. ohm LI.60. Post 101,
CARRIAGE AND PACKING EXTRA Approx. output of Hy-Lyght. Price [14.00. 100 WATT I /5/10/25/50/100/250/500/1k/ I .5k/2.5k1
OPEN TYPE I amp (panel mount) L9.00 Post 50p. 3.5k/Sk ohm 12.35. Post 15p.
HY-LYGHT STROBE MK III Black Silver, Skirted knob calibrated in Nos.
For use in large rooms, halls and utilises a silica 1-9. Ifin. dia. brass bush. Ideal for above 22p each.
300 VA ISOLATING TRANSFORMER tube, printed circuit. Speed adjustable 0-20 f.p.s. SIEMENS. PLESSEY, Etc
115/230-230/230 volts. Screened. Primary two
separate 0-I ISV for 115 or 230 volt. Secondary two
I ISV at 150 VA each for 115 or 230 volt output.
Light output greater than many (so called 4
Joule) strobes. £14. Post 501s RELAYS MINIATURE RELAYS
Can be used in series or parallel connections. Fully THE 'SUPER' HY-LYGHT KIT EVIW ohms
2 3 4

tropicalised. Length 13.5 cm. Width II cm. Height Approx. four times the light output of our well 58 5-9 6 c/o lOp
Weight 15 lb.
13.5 cm. proven Hy-Lyght strobe. Col. (2)
SPECIAL OFFER PRICE 1E5. Carr. 80p. Working ISO 4-9 2 c/o 70p
Variable speed from 1.13 flash per sec. 185 8-12 6M 60p
Reactor control circuit producing an intense d.c. volts
Col. 3 308 9-14 4 c/o 75p
A.C. MAINS TIMER UNIT white light. ONLY L22. Post 75p.
ROBUST, FULLY VENTILATED METAL Contracts 410 12-20 4 c/o (10p
60p
Based on an electric clock, with 700 16-24 4M 2B
25 amp. single pole switch, CASE. For Hy-Lyght Kit including reflector £5.75. Col. (4) 700 16-24 4 c/o BOP"
which can be preset for any Post 25P. Price 700 20-30 6 c/o 50P
period up to 12 hrs. ahead Super Hy-Lyght case including reflector 48. Post HD= 2,500 31-43 2 c/o HD 60p
to switch on for any length 60p. 2,500 36-45 6M 60p
Heavy duty 60p
of time, from 10 mins. to 7 -inch POLISHED REFLECTOR 9,000 40-70 2 c/o
6 hrs. then switch off. An Ideally suited for above Strobe kits. Price 55p. 15k 85-110 6M 60P
additional 60 min. audible Post 15p. 'Incl. Base All prices incl. P. & P.
timer is also incorporated. Ideal 6 VOLT D.C. I make contacts 35p. Post 10p.
for Tape Recorders, Lights, 6 VOLT D.C. 2 make contacts 75p. Post 10p.
Electric Blankets, etc. Attractive satin copper finish. COLOUR WHEEL PROJECTOR 9 VOLT D.C. RELAY
Size 135 mm x 130 mm x 60 mm. Price 62. Post Complete with oil - 3 c/o 5 amp contacts. 70 ohm coil. 75p. Post 10p.
20p. (Total incl. VAT and Post L238). filled colour wheel. 12 VOLT D.C. RELAY
100 watt lamp. 200/ 3 c/o 5 amp contacts. 120 ohm coil. 75p. Post 10p.
240V AC. Features 24 VOLT D.C. 3 c/o 75p. Post 10p.
PROGRAMME TIMERS extremely efficient op- DIAMOND 'H' Heavy Duty
230/240V a.c. 15 r.p.m. Motors. Each cam operates tical system. [18.50. 230/240V a.c. 2 c/o, 25 amp RES. at 250V a.c.
a c/o micro switch. Ideal for lighting effects, Post 50p. Post 10p.
animated displays, etc. Ex equipment tested. 6 INCH COLOUR WHEEL CLARE-ELLIOTT TYPE RP7641 GB
2 cam model. 12.00 post 30p. As used for Disco Miniature relay. 675 ohm coil. 24 Volt D.C. 2 c/o.
4 cam model. 12.50 post 30p. 6 cam model. 3 r.p.m. lighting effects, etc. Price 14.50. Post 30p.
6 cam model. L3.25 post 30p. L325 post 30p. 70P pest paid.
BIG BLACK LIGHT 100 VOLT A.C. 2 c/o sealed type, octal base
MINIATURE UNISELECTOR SWITCHES 400Watt. Mercury vapour ultra violet lamp. LI. Post 10p.
2 Bank, 1 position, 24 volt D.C. Powerful source of u.v. P.F. ballast is 24 VOLT A.C. 3 c/o. 75p. Post 10p.
I

operation, full wiper with an- essential Price of matched ballast and bulb 24 VOLT A.G. Mfg. by ITT.2 h.d. c/o contacts.
cillary contacts. NEW Price L16. Post CI. Spare bulb £7. Post 40p. SSp. Post 10p.
L250. Post 20p. As above but BLACK LIGHT FLUORESCENT U.V. TUBES 240 VOLT A.G. RELAY. Mfg. by ITT. 240V A.C.
with 5 Bank, 11 position. Price 4ft 40 watt. Price £550. Post 30p. (4ft to 10 amp h.d. c/o contacts. Octal plug in base. Price
L350. Post 20p. Personal callers only). 2ft 20 watt, [4.25. 75p. Post 10p.
Post 25p. (For use in standard bi-pin. MINI. 230/240 VOLT A.C. RELAY. Mfg. by Arrow 2 h.d.
I2in 8 watt, L1.60. Post 15p. 9in 6 watt, 15 amp c/o contacts. Amp connectors. Price £1.
COIN MECHANISM (Ex London Transport) L1.30. Post 15p. Complete ballast unit and Post 10p.
Unit containing, selector mechanism for I p, 2p and holders for 9in and I 2in tube, L1.70. Post 220/240 VOLT A.C. RELAY
5p coins. Micro switches, relays, solenoid operated 25p. (9in and I 2in measures approx.) 3 c/o 5 amp contacts. Sealed. Incl. 11 -pin base
hopper. 24 volt D.C. Precision built to high stand- £1.25. Post 10p.
ard. Incredible VALUE at only 1250. Post 60p. U.D.I. SINGLE CHANNEL HEAVY DUTY A.C. SEALED RELAYS
* 750 WATT MANUAL/AUTO DIMMER * 110V. 2 c/o. 20 amp contacts. L11.5. Post 10p.
230/250 VOLT A.C. SOLENOID 7m5.0nWn.77,1 iddeStItnetFnailnedr, nwith three functions.
VERY SPECIAL OFFER
Approximately 131b pull. Size of feet If" x I Is". * Automatic Cycling up andtwn.a.Fluen-dctoiwona *
Price 4100. Post 15p. * selected with 'three -position' rocker switch. * MINIATURE ROLLER MICRO
* Two ranges of cycling for 'Flashing' or 'Slow .4. SWITCH. 5 amp. c/o contacts. Mfg.
NEW. Price 10 for 11'50. Post 10p.
24 VOLT DC SOLENOIDS 2_ blending'. Ready built module 6' x 3' glass is
fibre board incorporating 10 amp TRIAC. (Min. order 10). Ditto press to make
UNIT containing 1 heavy duty solenoid approx. 2516 * Two or more modules for top quality colour * 20 for LI-50. Post 10p. Ditto press to break 20 for
pull 1 inch travel. Two x approx. I lb pull 3 inch travel. * blending and flashing effects. PRICE 115. * LI50. Post 10p. AS above less roller lever, 20 for
6 r. approx. 4oz. pull -3 inch travel. One 24 volt d.c., * Post 30p. L20. Post 10p.
I heavy duty single make relay. Price L2.50. Post 60p.
ABSOLUTE BARGAIN. t************* ** ** *** 230/240 VOLT A.C. MINIATURE MOTOR.
20 R.P.M. Price LI. Post 10p.
' 0-
230V FAN ASSEMBLY ELECTRONIC BODINE TYPE N.C.I.
Continuously rated, removable GEARED MOTOR
Pluminium Price LI. 14
ORGAN KIT
ost 20p. blades. Easy to build. Solid State. Two full octaves (Type J) 71 r.p.m. torque 10 lb. in.
(less sharps and flats). Fitted hardwood case. Reversible 1/70th h.p. cycle 0.38
PRECISION CENTRIFUGAL BLOWER Powered by two penlite 13V batteries. Com- amp. (Type 2) 28 r.p.m. torque 20
Mfg. Airflow Developments Ltd. plete set of parts including speaker, etc., lb. in R ibis. 1/80th h.p. 50 cycle 0.28 amp.
Heavy Duty continuously rated. together with full instructions and 10 tunes. The above two precision made U.S.A. motors are
smooth running, 230/240V a.c. Price L325. Post 35p. offered in 'as new' condition. Input voltage of motor
motor. Size: 16 x I4cm (case 115v A.C. Supplied complete with transformer for
only). OAL I Scm. Aperture
61, 230/2.40x A.C. input.
Price, either type [6.7.5. Post 50p or less trans-
6 x 6cm. £6.50. Post SOp. INSULATION TESTERS NEW! former L315. Post 40P.
Test to I.E.E. Spec. Rugged metal
230/240 VOLT A.C. EXTRACTOR construction, suitable for bench or 'FRACM0' 240 VOLT A.C.
FAN KIT field work, constant speed clutch.
Comprising of impeller, continuously Size L.13in. W.4in, H.6in, weight 61b. 50 cycle SINGLE PHASE
rated motor, motor housing and fix- 1.000V. 1,000 megohms, [34. Post
60p. 500V, 500 megohms, [28. Post GEARED MOTOR
ings as illustrated. Price L115. Post 60p. 33 r.p.m. 30 lb. ins. Reversible.
25p. (Total incl. VAT and Post a 16). Fitted with mounting feet.
Brand New. £14. Post 60p. (Total price incl. VAT
TRIACS 'GENTS' 6" ALARM BELL [15'77).
GENERAL ELECTRIC POWER-GLAS TRIACS 200/250V AC/DC. Brand New. Price £5. Post 60p
10 amp. Glass passivated plastic triac. Latest device HIGH VISIBILITY PANEL MOUNTING
from U.S.A. Long term reliability. Type SC I 46E 'STC' 6" RED ALARM BELL LED's. 0.25 inch mounting, 0.16 inch lens. Typical
10 amp, 500 PIV, £1.00. Post Sp. (Inclusive of data and 24/48 volt DC. Brand New. Price E4. Post 50p. parameters 2V, 20M amps all type. Supplied complete
application sheet.) Suitable Diac with snap in mountings and data. Red 4 for LI, Green
3 for El , Yellow 3 for LI. Post 10p. (in order) (C1).
600 WATT DIMMER SWITCH All prices are subject to
Easily fitted. Fully guaranteed by makers. LED READOUTS
Will control up to 600W of lighting
except fluorescent at mains voltage.
8°-b VAT. (8p in the £) 7 series, 141-1 d.p. one-third high
character. 14 pin D.I.L. Available in
Complete with simple instructions. To ail orders add 8% VAT to total RED or GREEN. Price C1.65. Post 10p.
C215. Post 25p. value of goods including carriage 4 for £6. Post paid.
packaging.
All Mail Orders -Callers -Ample Parking Personal callers only. Open Sat.
Dept. PEI, 57 BRIDGMAN ROAD
CHISWICK, LONDON W4 513B SERVICE 9 LITTLE NEWPORT STREET
LONDON WC2H 7JJ
Phone 01-995 1560
Showroom open Mon. -Fri. TRADING CO. Phone 01-437 0576

25
Practical Electronics January 1975
 ACOS
FOR
SOUND
ENJOYMENT

Magnificent Martin
Speakers
These restyled, popular
Hi-Fi speakers are avail- The Acos M6 Range of
able with an attractive Magnetic Cartridges are
wrap -around grill and a acknowledged to give
performance range to Acos Regs Record Deck high performance at low
suit any system. Brilli- Elegant, modern styling cost for two channel and
ance controls are pro- with first-class perform- four channel stereo.
vided which help to fit ance.
them into any setting.

"C", ("es

Acos Eleanor Range of

two channel and four
Acos Lustre Tone Arm channel stereo tuner amp -
Proven quality tone arm lifiers provide a new
for the enthusiast, incorp- concept of sound enjoy -
orating 'dial -a -magnet' ment in any home
anti -skating. setting.
Use Acos Care
Accessories
Stylii and replacement
cartridges for your
continued sound
enjoyment.

Cosmocord Ltd, Eleanor Cross Rd, Waltham Cross, Hertfordshire EN8 7NX
Telephone: Waltham Cross 27331, Telex 24294.

Please send me full details of NAME

ADDRESS

26 Practical Electronics January 1975

 PE
THE TRIUMPHS OF RADIO ASTRONOMY
THE charting of unimaginable depths of space has been
assiduously carried out by radio astronomers in a num-
ber of countries since this science was formally established
some 30 years ago. In Britain we can be especially, proud
of the achievements of our own radio astronomers, in par-
ticular those at Mullard Radio Astronomy Observatory, Cam-
bridge, who have reached out to the furthermost parts of
the Universe. And now has come international recognition
and reward. Two scientists chiefly responsible for the signi-
ficant discoveries at Cambridge have been awarded the 1974
Nobel Prize for Physics (see page 38).
The triumphs of radio astronomy are scintillating examples
of pure science working hand in hand with technology in
the quest for. knowledge of the very Universe itself. Un-
doubtedly this young science does deserve more general
recognition.
Lacking any dramatic dynamic action and readily assimilat-
able evidence like, for example, that which accompanies each
Space Shot, radio astronomy has remained a distant and
little understood or appreciated science so far as the general
public is concerned. Radio telescopes in the popular mind
are parabolical structures that can be rotated and aimed at
any desired part of the sky, as exemplified by the very
familiar Jodrell Bank telescope. In reality, radio telescopes
can take diverse forms, and as often as not consist of static
arrays of aerials bearing no resemblance to the general con-
ception of a "telescope'..
The emissions received from the far-off radio sources are
recorded and provide data for computers and mathemati-
cians to digest. It is only after the scientists have performed
their analysis that the results can be presented in more
tangible form that will be meaningful to the non -expert.
This is of course in contrast to optical astronomy. Armed
with even a modest telescope, anyone can make observations
from his back garden. The results obtained will differ, essen-
tially, only in degree of magnitude of resolution and distance
covered with those of the professional optical astronomers.
With radio astronomy, as we have indicated, the observer Editor
has to be an expert interpreter, while the apparatus employed F. E. BENNETT
will comprise complex aerial arrays and highly sensitive
receiving equipment-often unique and specially developed Editorial
R. D. RAILTON Assistant Editor
by members of a radio astronomy observatory staff for par- D. BARRINGTON Production Editor
ticular kinds of observations. Thus at both levels, science G. GODBOLD Technical Editor
and technology, radio astronomy is almost exclusively the S. R. LEWIS B.Sc.
domain of the professionals. And in addition, so far as Art Dept.
the larger observatories are concerned, generous financial J. D. POUNTNEY Art Editor
backing is essential, from government or industrial bodies. J. A. HADLEY
This does not mean that the amateur is precluded from R. J. GOODMAN
K. A. WOODRUFF
undertaking any investigations in radio emissions from extra-
terrestrial bodies. But it does mean that from practical Advertisement M
considerations he is restricted to observations of the Solar D. W. B. TILLEARD
System, our own Galaxy, and the more powerful sources of Phone: 01-634 4202
nearby galaxies. Here he will be following in the footsteps P. J. MEW
of the professionals, whose early work included extensive Phone: 01-634 4210
examination of these regions and, we should note, they C. R. BROWN, Classified
themselves were following the pioneer investigations made Phone: 01-634 4301
by an American amateur named Grote Reber. It is indeed
all too easy to assume that no significant discoveries are Editorial 6 Adverti4ing Offices:
Fleetway House. Farringdon St.
likely to reward amateur efforts today. But does one really London EC4A 4AD
know for sure? Phone: Editorial 01-634 4452
F.E.B. Advertisements 01-634 4202

January 1975 27
Practical Electronics
 DEC ORA,
.0G rfolif
P:"
... MAKE THIS
LIGHT
PIPE
MOBILE light displays -e all the rLge nowadays FAIP 1
I
PAIR 2 VW. ) 'ArA t. F.AF5 ETC
w th mu ti-ccicured displ. ys driver. 3y ampli- 1st a-.11b2,11:Alt
fiers a commor felcure of parties and dz.rc,m, The
flexi3ility of elect -arks Items not yet been eirloited
1
\.)
fully in this area but this Article, deicrib.rg L plastic 3\1
pipe dowr which light can be made to seem ID flow, TIME
shcws the potential available to c3nstrtrtors wit.i 0` 3
im4inaticn.
The ligtt pipe consist, (.." a plastic ti -be 241t long.
containing 144 miniature light bulbs whizh are
4
1\3 C\1
flashed in a sequence which banes of light Fig. 1. The first ten tulbs in -be Light P pe showing the
appear to move dowi the tcbe. four swi-cting sates, 0 being the off cundlition and 1
the on concitien. The diagonal pattern indicates the
The bulbs are cooirected in four se-ies chants of 36 apparent dioecticn of light notion
bulbs, and at aly tire tw3 adjacent bulbs are or
and wo are off. Ttis pattern is. reneatecl 36 times THE CIRCUIT
dowr the tube z nd to give the. effec- of rraxicr, the The c rccit di igr im of --ig. 2 indizates the basic
 ON/OFF, SPEED
SV

to IV Pin 4
RS RR
IC2,3,4,5, Pin 14
12 12
Kit
R1
S1 a D5Io08
0 4 KIN 4001 TR1
R6
D5 +
N
D6
'CI C2, 4
3-3
kfl C3.4oF
1+ 60r)
FS1
I I

ODBC108-4'
414
0
0
0 to ICI Pinil
4,5,Pin 7
Sib R4
1E1 -..-C Ft1/5
SKI
LP1 P17 P73 P109
/5
to 1 to 1 to , to
LP36 LP72 LPIOR ,LP144

PL1/2 PL1/3 PL1/4 PL1/1

SK1/3 SKI/ SKI/1
DI R3
/2SKI CSR1 CSR2 ICSR CSR4
47
kn

DitoD4 4X1N4005

SN7473 SN 7400 567400 567400 567400

ICI 1C2 1C3 1C4 105
3 11 13
2 8 a
12 12

4 a
6
. 9 a
9 9

10 10
12
5
12&11 a
4
10

a a
B
2

Fig. 2. Complete circuit diagram of the Light Pipe

system showing the four columns of bulbs in dashed
line. Note that the live side of the mains supply is
connected to the logic OV line through D4 and thus
IC5 inverts the signals and directly drives the care is required in ensuring insulation of the circuitry
gates of the thyristors. from the case and controls
The zero -crossing pulses for IC4 are produced by
TR2, which is on until the supply to the lamps falls
below a given level. Check the board carefully for shorts between
adjacent strips and for strips not cut in the right
POWER SUPPLIES place. Note that there are not always seven cuts
The logic 5V is obtained from a 6V transformer, underneath i.c.s as sometimes it is necessary to join
rectified to give 8V d.c. regulated at 5V. The lamps the opposite pins.
are driven from full -wave rectified mains, so that The thyristors used in the prototype had their
the thyristors are operational in both positive and anodes connected to their heat sinks. The wires to
negative half cycles of the mains. The thyristor the output socket were soldered to the heat sinks
cathodes are connected to logic OV, which means rather than to the anode wire on the Veroboard,
that this is not at the same potential as earth and as this was more convenient.
no connection should be made between this and The five -way connector used for the output should
the case, which is earthed for safety. be as non-standard as possible for safety. A five -pin
DIN would work but is almost bound to be connected
CONSTRUCTION to audio equipment at some time.
As a wrong connection could have dramatic THE PIPE
results, it is suggested that construction is done in
stages, and each stage checked. The best order is The bulbs used in the prototype pipe were 8V,
logic power supply, multivibrator, counting and 150mA, I mm diameter, Vitality type no. G537.
I

decoding i.c.s, mains rectifier and thyristors, and zero A supplier for these is mentioned in the components
crossing pulse generator. list. They are a tight squeeze in the pipe, but once
The Veroboard cuts and component layout are installed, the pipe may be bent round fairly sharp
shown in Fig. 3 and the accompanying photographs. corners without danger of them breaking.
Individual constructors will no doubt modify this as If a smaller bore pipe is being used, there is an
they see fit to accommodate components of differing electrically similar type, the 676W /E, which is
dimensions. wire ended and much smaller. They are, however,
Practical Electronics January 1975 29
 6V TI

ISC108
anode

Fig. 3. Component layout and Veroboard cuts and interconnections for the
Light Pipe showing connections to unmounted components
more expensive, and come in packs of 200. These
are available from the same supplier.
As the lamps are somewhat inaccessible in the
pipe it is important that there are as few failures as
possible. The lamps are considerably underrun to
increase their life. This also reduces light output
and hence temperature. The pipe should be mildly
warm after a few minutes running, but there is no
danger of the plastic melting.
CONSTRUCTION OF THE PIPE
First, solder the bulbs into four chains of 36 bulbs.
There should be 8in between each bulb for an
overall length of eight yards. The connecting wire
should be as thin as possible and multistranded.
Some sort of jig to hold the bulbs while soldering is
of great help in speeding up the operation.
The chains should be tested on the mains at this The four chains should be laid out so that there
stage to find any blown or broken bulbs, or dry is 2in between each bulb, and taped together at
joints.
intervals with a fifth common wire. The pipe is pre-
Plastic pared for insertion by blowing talcum powder down
disc it.
This reduces friction which otherwise might
impose too great a strain on the bulbs during
Transparent pipe insertion.
To thread the lights, a piece of string must first
repeated 36 times
be put through the pipe, using a piece of iron or steel
along tube unction tied in and a magnet to pull it through. The string is used
place atend of to pull the light chain back through. The bulbs
pipe
should be pulled through with great care in order to
avoid damaging them where the lead -out wires
emerge from the envelope if the 676 type is used.
Tape leads together
at intervals
It is easier to fix the string at the far end of the
pipe, and pull the pipe over the lamps, with liberal
addition of talcum powder if it is difficult to pull.
amnion lead P11/5 The common wire should be joined at one end to
Chains to
PL1/1, V2,1/3 and 1/4
the four other wires and held at the end by tying
a piece of wire round the joint and tying this to a
Fig. 4. Sketch showing the method of tying the light piece of plastic which is glued over the end of the
bulbs to draw them through the pipe. Note that par- pipe.
ticularly with the wire -ended bulbs the taping of the The wire leading to the pipe is two yards of five -
various conductors between each bulb is important core (four -core + screen audio will do), with a suit-
in protecting the bulbs during installation able plug, of which any metal parts should be well
30 Practical Electronics January 1975
insulated from the pins. The joint between it and the
pipe is hidden by wide insulating tape wrapped
round the pipe. The far end is similarly covered to
improve appearance.
FAULT FINDING
In the event of a lamp failure, it is easier to cut
into the tube and replace the lamp in situ rather
than pull out all the lamps and . deal with it
externally.
The bulbs which have gone out should be marked
on the outside of the tube with a felt pen. Then by
pushing a pin through the tube it is possible to make
contact with one side of the bulb and the continuity
between it and the common line can be tested. If
the first test is done in the centre, further tests can
be made to subdivide the faulty section until the
blown bulb is found.
Whilst cutting the tube might seem drastic it is setting adhesives now on the market such as Thixofix
certainly simple and providing a sharp knife or or Araldite. Also the cut is usefully 'U-shaped rather
scalpel is used to give a clean cut it is not difficult than through the whole pipe.
to re -glue the cut faces using one of several fast
DEVELOPMENTS
COMPONENTS . . . The direction of apparent motion may be reversed
by reversing the anode wires to CSR1 and CSR3,
Resistors and if desired a switch may be included for this
R1 1000
R2 470k
function.
R3 4.7k0 There is no reason why several pipes may not be
R4 1 kf/ run off the same controller as the thyristors are
R5 1.2kD rated at IA and each chain takes only 150mA. It
R6 3.3kD could be arranged, to flash coloured lamps as well as
R7 10kD the light pipe, provided the current is kept well with-
R8 1 2k12 in the ratings of the thyristors. 3A types could be
substituted with no circuit modifications if a high
Potentiometer power output is needed.
VR1 220ki2 linear with double
pole mains switch Any increase in demand for current will of course
Capacitors affect the choice of diodes DI to 4 and these will
C1 640tiF 10V electrolytic need uprating if demand exceeds 1A.
C2, C3 4tiF 10V electrolytic (2 off)
Lid with Potentiometer/
Switch
Transistors Mains Input
TR1-4 BC108 (4 0) lead

Diodes
D1-4 1 N4005 (4 off)
D5-8 1 N4001 (4 off)
D9 5 6V Zener
Integrated Circuits
IC1 SN7473
IC2-5 SN7400 (4 off)

Thyristors
CSR1 to 4 CRS1/40 (1A, 400V)
Miscellaneous
144 type G537 8V 0.15A bulbs
(Vitality) (Townsend -Coates Front of
Ltd., Coleman Road, Leicester, Box
LE5 4LP. Valiant Electrical
Wholesale, 20 Lettuce St.,
Fulham, London. Farnell Elec-
tronic Components)
8 yards green polythene tube
(o.d. 2.3cm, i.d. 1.6cm) (Trans- CSRI/CSR4
atlantic Plastics, Surbiton) et (for order of mounting,
see Veroboard layout)
Aluminium box type AB13
Veroboard 24 strips x 36 holes
Transformer Eagle MT280 6V,
280mA
Suitable 5 -pin socket and plug Veroboa-d mounted in Box
via 2-6BA X6mm long Spacers
assembly. 1A fuse and fuse -
holder Fig. 5. Interwiring diagram
11
Practical Electronics January 1975
 Electrode making and breaking is sensed by TR1
and here one of the prime requirements is to keep
the current that flows through the sensor, when
covered with water, as low as possible to reduce the
effect of electrolysis which would soon fur -up the
two electrodes.
With no water bridging the electrodes TR1 base
is open -circuit therefore the collector is almost at
supply potential. As soon as the electrodes are
bridged the base goes high turning TR1 on, the
collector then going to 0 volts.
At this stage it could be argued that no further
circuitry is required other than a relay or thyristor
to switch the mains. This would be fine if water
behaved to our liking, but in fact this is not so.
Once the sensor has been exposed to the atmosphere
for some time the surface becomes slightly greasy.
This causes the water droplets to have greater surface
tension which means in practice that the sensor must
be fully covered with water before the spray is
stopped or intermittent operation of the circuit will
take place, settling down once the surface has
accumulated enough water.
TIMER
However, to overcome this problem and to give
more choice of control a timer has been added. This
takes the form of the now well-known 555 i.c.
(IC2) discussed in depth in June 1973 PRACTICAL
ELECTRONICS.
The 555 is used in the monostable mode and thus
the trigger pulse must be shorter than the timing
period. Differentiation of the input signal is
BYJ.S. HAGGIS achieved by R4 and C3. In order to provide a sharp
pulse edge a Schmitt trigger is required and this also
ONE requirement for greenhouse owners whether provides jitter -free operation.
amateur or professional is a system for keeping The Schmitt used is a monolithic integrated, 14
leaf surfaces moist. This is achieved by spraying the pin package, type SN 7413 (ICI). The package con-
leaves, at intervals, with a fine water mist. The tim- tains two identical triggers. Each circuit functions as
ing of the intervals depends, on the rate of evapora- a four input NAND gate. All four inputs are held
tion at any one time. This article describes the high by internal resistors and in this condition the
principle, theory, and construction of a device that output is held at logic 0. Any one input going to
will automatically control this process. logic 0 sends the output to logic I level, i.e. 5V.
The system uses a sensor which consists of two If any constructor wishes to omit the timer circuit
electrodes placed approximately }in apart and cast in and chance any intermittent switch -off, he can do so
and Araldite block. The surface of this block is by leaving out the timer package and associated
machined flat so that when it is sprayed with water components.
the two electrodes eventually become bridged with
a blob of water. If no further spray is directed at
the surface. evaporation soon starts to reduce the
amount of water bridging the electrodes, until
finally the bridge is broken. The time taken for this
to happen depends on the rate of evaporation. On a
hot summer day the time will be short,- whereas on
a damp cloudy day the time will be longer.
PRACTICAL CIRCUIT
The making and breaking of the sensor circuit
can be used to operate the electronic circuit of Fig. 1.
At first sight this might seem rather complex for
such a simple operation, but as will be seen later the
system allows for quite a degree of control, coupled
with sound operation and reliability.
The object of the circuit is to actuate a standard
mains operated solenoid water valve to feed water
to a mist propagator when required, and to do this
with no moving parts except the solenoid valve, i.e.
relays, thus eliminating any trouble from corroded
contacts which can easily happen in the greenhouse
environment.

32 Practical Electronics January 1975

 813 614

VIEWED FROM TOP 412 )11) R15

a pco
RII 3
4 5
6 0' 7 R16
FOR RESISTOR
8o-+
/\
6073 VALUES SEE TEXT 4-02.00.000
b 2N2926
R10 9 RI7

MT MT
I 2
I

Cl
\le R9
1000 a,"
Ck/RI8
TO SENSOR 51
VIA SKI PLI (SEE TEXT)
562
L
02 1,4,
S2a WATER
+5V VALVE

°3 1544
r
R1 R2 R3 NA R5 R6 R8
35
560 68 160 2.2k11 I Oki) 10k0 1800
1807

LP1 I 0
C3
I 2 MT2
6
5147413 NE 555V
DI 1pF
13 5 MT1
CSR1
04-7 2146073
TR1
3V

f-lc6
CI
220pF 2N2926
C2
0.22}.1F 0 2pF T
CLMim mim CS
OlpF

N0-10.44410 T'D'PF
S2b
EO TIMER SWITCH
POWER SUPPLY SENSOR SCHMITT

Fig. 1. Circuit diagram of the complete plant moisture control system. Note that the earth line is connected
to the case of the control valve if possible and to any metal case parts if these are used

CIRCUIT DESCRIPTION COMPONENTS . . .

As can be seen, the power supply is not special.
The 5 volt rail is Zener stabilised whilst the mains Resistors
transformer TI is an R.S. Components Ltd., sub. R1 56 R6 10k
min. 3-0-3V device rated at 200mA. The total circuit R2 6.8k n R7 180 S2 See text
R3 1k SI R8 180 12 See text
consumption is 45mA. Even so the transformer gets R4 2.2k n R9 to R18 See text
quite warm but long tests have been given to the R5 101(12
prototype with no ill effect. All watt carbon
As stated earlier, when the sensor X1 is bridged
with a blob of water the collector of TRI is at Capacitors
OV. This state is fed to that trigger input whose C1 220µF elect. 40V printed circuit type
output under these conditions is high. The require- C2 0.22µF disc
ment is to have a high output on C3, because the C3 1µF non -elect 63V Wima
timer is started by a falling voltage. C4 0.214F disc
C5 0.01µF disc
When the blob of water has evaporated sufficiently C6 100µF electrolytic 63V Wirna
to break the contact between the electrodes of the
sensor, the base of TRI becomes open circuit and Semiconductors
the collector goes high. Thus the output of the TR1 2N 2926
Schmitt goes low and starts the timer, the output of CSR1 2N 6073
which goes high, to approximately 5V. This is IC1 SN 7413
applied through a resistor to the gate of CSRI thus IC2 NE 555V
turning it on. D1 4.7V, 1.3W Zener BZX61 series or
The time the output of the timer remains in this IS2000A, IS7000A series (Doram)
D2 and D3 1S44 (2 off)
state is determined by the setting of SI which selects D4 to D7 Rec 70 (800mA 400V) Doram (4 off)
the series resistors R9 to RI8.
The electrodes can be bridged again with the Miscellaneous
spraying water with no further effect on the timer. T1 3V type 200mA. Doram
Once the time sequence is ended the circuit is set SK2/PL2 Jack and socket min.
for the next sequence when evaporation dictates. Case Sarel Ref. No. 308 from Hawnt and Co. Ltd.,
A brief look at the circuit diagram will reveal Pritchett Street, Birmingham B6 4EN.
a direct connection through diode D2 and resistor Mains cable 3 core P.V.C. Circuit board. Rubber
R8 from the output of the second Schmitt to the flex Neon indicator
connector (Woolworths).
gate of CSRI. 250V miniature.Knob and dial skirt 'C' sin.
Doram. Midget rotary switch pole 12. way. 1
This has two functions, the first being if the Miniature toggle ON/OFF switch. Mains fuse and
operator wishes the sensor to control the "off" time socket. Materials for sensor. Solenoid valve-
as well as the "on", and accept the possibility of an see text.
unstable switch -off, he can do so by turning the time
33
Practical Electronics January 1975
 25mm

10mm
8mm die Carbon Rods
Note disposition of Tube t
Rods and Needle with
respect to Plastic
Tube t 2

Plastic Tube
filled with Araldite

No 6 Knitting
Fill flush to top of Needle
Tube with Araldite pprox 80mm long

Scrap of soft
Wood for bast

Fig. 2. A completed sensor (above) showing the

dimensions in mm and simplicity of construction
Fig. 3. Manufacture of the sensor is also simple using
this jig made up from a bit of scrap wood (left)
Make holes in base for
placement of Rods and Needle

carbons and even roll off the surface if the design

is not correct.
control to its minimum. Thus when the water breaks
the contact the collector, as before, goes high, and SENSOR CONSTRUCTION
starts a timing cycle which with the control turned The sensor is best cast in a piece of plastic pipe
to minimum, is only in the order of Is and therefore with a lin inside diameter. This has two advantages,
of no consequence. the first being ease of casting and the second and
But the second Schmitt output volts are applied more important being that the plastic edge surround-
'direct to CSRI gate and this turns on CSRI for as ing the sensor surface tends to prevent the blob of
long as the electrodes remain open. Each Schmitt water from rolling off.
within the package inverts therefore the output from The two carbon rods can be obtained from any
the first Schmitt must be fed into the input of the used -up U2 type battery, the metal cap ends being
second which is in turn used for direct control of used to solder the wire connections.
CSRI . Cut the two carbon rods at lfin long from the
Without the D2, R8 connection and the timer metal cap end. Drill two holes Kin dia. at fin
interval inadvertently set too short to allow full centres, in into a piece of scrap softwood. Drill a
coverage of the sensor with water, the timer would third hole to one side, as indicated in Fig. 3 to
be triggered as before thereby turning on the spray. accommodate a No. 6 plastic knitting needle.
But if the spray were to cease before the sensor was Push the two carbon rods into the holes as far
properly bridged, no further action could be taken by as possible. Acquire a 4fin length of No. 6 knitting
the circuit. In fact if man did not intervene the cir- needle (sharp end if possible) and insert the blunt
cuit would remain stuck in this state for good. But end into the third hole as far as it will go. Next
with the direct connection from the Schthitt this can- place a 1 fin length of lin inside dia. plastic tube
not happen. The two diodes are to prevent any pos- over the carbon rods and needle. All is now ready
sible interaction. to attach the wires. Any twin cable with a plastic
outer sheath is suitable. Solder one wire each onto
SENSOR the metal caps of the carbon rods. Ensure that the
The sensor X I consists of two A in carbon rods cable sheath is below the edge of the tube so that
cast in Araldite at -tats in centres (see Fig. 2). it will be well covered with Araldite.
The design of the sensor is quite critical. The When all is ready mix the Araldite resin as
relationship between the total diameter of the sen- directed and heat until it runs quite freely, then pour
sor, the diameter of the carbon rods, and their it into the plastic tube ensuring that air bubbles are
separation distance is important. Because of surface not trapped. Rotate the tube a little and position
tension the blob of water that forms on the top of correctly round the carbons. Leave to set over night.
the sensor can roll about the surface and avoid the One packet of Araldite is sufficient.
34 Practical Electronics January 1975
 TO TO TO TO
EARTH 52b LP1 FS1

Fig. 4. Component layout on the prototype printed

circuit board

Once the Araldite has hardened the timber can be operating the water valve manually, the jack socket
split from around the ends of the carbon .rods. Saw is wired such that when the jack is withdrawn the
the carbons and needle flush across the surface of base of TR1 is left open circuit, thereby turning on
the sensor and then sandpaper the surface flat, finally CSR1 for as long as the jack remains out of the
finishing with a very fine sandpaper. Wipe the sur- socket.
face with methylated spirits. The sensor is now ready C2 should be mounted as closely as possible to
for use. the Schmitt input. This is best achieved by solder-
ing it directly onto the package pins.
CIRCUIT CONSTRUCTION
In the prototype all components were mounted onSETTING UP
one printed circuit board, including the mains trans- First ensure that the circuit has the correct d.c.
former as shown in Fig. 4 and using the circuit lay- voltage, 5V, and if not change the value of R1
out of Fig. 5. If any constructor wishes to alter this accordingly. For most practical purposes a maxi-
arrangement there is no problem, the layout is not mum time value of 100 seconds in 10 second steps
critical other than the necessity to adequately separ-
ate adjacent conductors carrying 230V a.c. Fig. 5. Printed circuit master as used in the prototype
It might be noted here that the whole circuit is Leaf
connected to the mains neutral line and care should
be taken when handling the circuit board when
switched on as full mains potential is on the board.
Preferably the board should not be handled at all
when power is connected.
The board is housed in a Sarel box measuring 41
x 23 x 2in. The Sarel boxes are made from a tough
plastic and are waterproof which makes them safe
when containing mains in possibly damp conditions.
The three core mains lead enters the box through
a tight fitting grommet and may either be wired
direct into a fused distribution box or connected to
the mains via a fused standard square pin 13A plug.
It is suggested that this cable be black.
The cable to the load, in this case 'a water valve,
again leaves the box through a tight fitting grommet
and is terminated with a three pin rubber flex con-
nection to which the water valve may be connected.
It is suggested that this cable be white to eliminate
any possible confusion.
The sensor X1 is plugged into the box using a
normal jack plug PL1 and socket SKI. To enable
the circuit to be tested or as a convenient way of
Practical Electronics January 1975 15
is quite adequate. But if longer or shorter time inter-
vals are required it is only necessary to change the
value of C6, andlor the values of R9 to R18 on
the rotary switch SI.
SI is a midget rotary 12 way switch set to give
II positions and assembled with knob and dial skirt
"C" in order to give indications from 0 to 10.
With C6 at 100.F and a maximum time of 100
seconds required, the total value of R9 to R18 is
approximately 50010.1. This will vary according to
tolerance spread of different condensers.
In order to test and set-up the circuit, connect
a 60W mains bulb in the load position SKI, pins 1
and 2. This gives clear indication of the operation of
the circuit. Then stand the sensor up and cover the
sensing surface with a small piece of very wet blot-
ting paper. Turn the rotary switch to the 0 position,
plug in the sensor, apply the mains and switch on.
If all is working correctly the bulb should light
up as soon as the wet blotting paper is removed and
remain lit as long as the paper is off the sensor.
Replace the blotting paper and the light should
extinguish about I second later.
If when the bulb is lit, it appears to flicker and
not to be at full brilliance it is because CSR1 is not
switched fully on. This could happen because of
variations in sensitivity of individual devices and can
be rectified by reducing the value of R7 and R8.

Stick the sensor spike into the soil at a con-

venient spot amongst the plants to be sprayed, but
TIMING RESISTORS not covered by them. Wipe the top of the sensor
If all is well up to this stage it now only remains with some methylated spirits to remove any grease.
to fit the individual timing resistors around SI. Select position 0 and switch on noting the length of
Solder into the first position a 47ki1 resistor and time required for the sensor surface to become
select on the dial (remember all these numbers on
I covered and the system to switch off.
the dial are x10). Then with a suitable time piece It is unlikely that subsequent operations will take
handy, remove and replace the blotting paper and as long as the first because the subsequent operations
note the length of time the bulb stays illuminated. will not be starting from a dry surface, but an idea
With preferred resistor values it may be difficult to of the time required can be gained. The unit can
time precisely, but times within 10 per cent can be now either be left on "0" and control its own switch
achieved. If for instance, the 4716/ gives 11 seconds off time as stated earlier, or set to a time interval as
instead of the required 10 seconds, then in the next suggested by the initial timing. Experience will soon
position solder a 33k12; this should then bring the 20 enable a useful setting to be found.
second timing to about 18 or 19 seconds. It is pos-
sible by carrying on in this manner to stay quite MAINTENANCE
close to the required timing. More accuracy can be The only maintenance required is an occasional
gained, if required, by making use of resistor wipe of the sensor with meths.
tolerance spread. If at any time it is required to test the unit it is
The repeatable timings of the circuit are very good only necessary to remove the sensor jack and replace
and this is what matters most. It does not matter it again and the system will operate for as long as
much that a time of 62 seconds is given when 60 is the selected time interval set.
wanted as long as it repeats.
SOLENOID VALVE
The choice of valve used depends on the water
pipe system in use, water pressure and availability.
INSTALLATION The author used one from C. W. Wheelhouse &
Securely mount the control box and connect the Sons, 9-13 Bell Road, Hounslow, Middx. which had
circuit to the mains through a fuse box or a 13A lin B.S.P. fittings.
square pin fused plug fitted with a 3A (or there- The EVJDIO and the EVD15 are fin B.S.P. male
abouts) fuse. Connect up a suitable mains operated and female fitting valves from Danfoss (London)
water valve for the spray system. Ltd.,6 Wadsworth Road, Perivale, Greenford,
CSRI is rated at 4A and this load should not be Middx. Both cover most water pressures which will
exceeded or damage will occur. There is little advan- be met and are available from stockists at around
tage in fitting a fuse because in general CSRI will £12.
blow before a fuse. If it is required to switch A d.c. operated valve could be accommodated by
greater loads it will be necessary to select a different using a transformer to supply the correct voltage and
CSRI. a suitable rectifier.
36 Practical Electronics January 1975
 MERCURY AGAIN problem. The state of the individual
The second visit to Mercury by readily adapts to the return to
Mariner 10 confirmed the previous Earth with no resultant effects. This
assessment generally. The second settles the problems that were
fly -by was 50,000km. More than 500 thought to exist for long missions
high resolution pictures have been into space.
received, all of excellent quality. Many ways of overcoming the
This pass was entirely on the sunlit weightless condition have been
side of the planet and covered some investigated and these are no longer
areas that had been checked on required. All that is needed for an
thefirst pass in March last year. astronaut is a programme of physi-
There were no startling new dis- cal exercises for 90 minutes each
coveries. day during the flight.
The hemisphere observed showed
that the planet has only one large ASTRONAUT PERFORMANCE
impact basin. This area known as In each of the Skylab missions
the Colaris Basin was on the ter- there was a progressive improve-
minator at the first pass. The floor ment in astronaut performance. This
of the crater would seem to be was due mainly to the increased
about the size of the Mare Imbrium exercise taken. The first crew were
of the Moon. so occupied with the various tech-
Many craters seem to have a cen-
tral peak which suggests that the
terrain was extremely soft at the SPACEMEN nical problems that arose; little time
was available for an intense study
of the exercise aspect. Even when
time of impacts. There are also BY FRANK W. HYDE the extra vehicular activities con-
many craters within craters. A num- tinued to six hours at a stretch
ber of rayed craters exist and there there were no "clinical" events to
is one large area near the south record.
pole with the rays extending out Uranus is imperative because of the No signs of heart deterioration
through other craters. The south sparse data as to the exact
pole is inside a large crater. appeared but there was the usual
ephemerides of these bodies. loss of red cell mass, this
There seem to be two distinct Previous navigation of deep space reduced as the exercising was
types of configuration of craters, missions have relied on Earth -based extended and the flights were longer.
those which are concentric and radio measurements. Mariner 10 Thus the first mission crew lost 14
those which are in long chains. The carried out a real-time experiment per cent, the second crew 12.3 per
concentric craters seem to be of as it approached Mercury. Over a
the order of 200km in diameter. hundred pictures were taken to
cent but the third crew loss was
Another feature is the large num-
down to 6.8 per cent. As on the
show the angular between Mercury Apollo missions there was a wide
ber of random scarps hundreds of and the nearby (optically) stars. variation between individuals.
kilometres long and of heights of The experiment was successful and Post recovery was better in the
the order of one to three kilometres. this means that spacecraft on long case of the last mission of 84 days.
The stresses shown are compres- distant missions will be able to con- The astronauts on the last mission
sional and the result of the com- tinuously monitor the space ahead lost least weight. Most of them
pression produces these scarps. and therefore automatically adjust gained in height, this averaged
They appear to be random in direc- course. about an inch. There was a shift-
tion and do not follow any particu- Provided Mariner /0 can limit its ing of the body fluids. Some of
lar pattern. The scarps appear to fuel for modifying its course and the crew experienced slight malaise
be antipodal to the Colaris Basin not suffer another distraction for the first two or three days.
and a similar situation is indicated because fast particles interfere with However, all got their "space legs"
on the Moon in relation to Mare the sensor which is locked on Cano- in a day or so and thereafter were
Imbrium. pus, it should be possible for the immune.
It would appear that the condition spacecraft to make another pass of The calorific requirements
in which Mercury is now found fits Mercury in 1975. proved to be the same or there-
in very well with the current theories abouts as their normal routine on
of early development of the Solar Earth.
system. This means that there was MORE FROM SKYLAB Testing the ability of these men
a huge infall of large bodies on the Adding to the preliminary reports as observers of the Earth from
emerging planets followed by a that have appeared about the effect space, an analysis made of the
period of high internal heating with of weightlessness and the general observations and the ability to carry
volcanic activity. This takes care of ability of the astronauts to be in out the tasks allotted showed that in
the changing surface features leav- a condition to carry out their tasks, 850 observations and some 2,000
ing the primordal conditions hardly some particular findings are now hand held camera shots, during the
discernible. available. These were released at 84 days' mission covering 83 widely
a symposium arranged by the varied categories, led to these con-
American Astronautical Society. clusions. The ability to recognise
OPTICAL NAVIGATION IN Altogether there were 171 days of objects and patterns, to integrate
SPACE free orbital flight during the Skylab these observations from a wide
Another important experiment mission and not only has it been range of aspects and lighting angles,
carried out by Mariner JO was to demonstrated that man can adapt to reason, to make selected obser-
test the optical techniques for navi- indefinitely to the weightless vations and describe them brings a
gation. These techniques are vital environment, it has also shown that new dimension into play. This
to the missions to outer planets. provided there has been adequate ability transcended anything that
The need to be able to dodge the exercising during the mission the could be programmed or made
satellites of Jupiter, Saturn and return to normal gravity presents no automatic.

Practical Electronics January 1975 37

 MAPPING RADIO GALAXIES AND QUASARS
NOBEL PRIZE Leading on from the far -distant -source discoveries,
the next successful objective was the mapping of the
radio galaxies and quasars. The properties of the galaxies
FOR CAMBRIDGE RADIO ASTRONOMERS were of particular interest because they are enormous
wasters of energy and among the largest objects known.
By Frank Hyde The detailed mapping of the galaxies and quasars
enabled some conclusions to be drawn as to their birth,
evolution and final demise. In this area Ryle not only
T HEhadannouncement that the Nobel Prize for Physics
been awarded to Professor Sir Martin Ryle
made the initial discoveries but also showed that the
exploding galaxies threw out on each side large clouds.
FRS, now the Astronomer Royal, and Professor Anthony These clouds appear to interact with the inter -galactic
Hewish FRS, is a fitting reward for the work of these medium. These great radio clouds seem to continue to
two quiet and unassuming men from the Mullard Radio receive energy from the optically observable nucleus of
Astronomy Observatory. It is a far cry from the angle the original galaxy or quasar for millions of years.
iron and wire structures, which began a series of pro- In 1964 at the International Astronomical Union
grammes more than two decades ago, to the 5km radio meeting in Hamburg, Anthony Hewish released the
telescope now in operation at Lord's Bridge near details of his method of finding quasars by their scintil-
Cambridge. lation. A quasar is to the radio telescope a small object
The official citation for the award ends with these of high intensity. The interplanetary medium gives
words "for their pioneering research in radioastro- changes of density with the same effects as the atmos-
physics: Ryle for his observations and inventions, in phere on light coming toward the Earth. The small
particular the aperture -synthesis technique and Hewish apparent diameter of a quasar is comparable with the
for his decisive role in the discovery of pulsars". variations. In consequence a quasar is revealed by the
Ryle, together with Hewish and Graham -Smith, were amount of scintillation that takes place.
the original team. Hewish has stayed on but Graham - The preliminary work on this problem was undertaken
Smith moved to a Professorial Chair at Manchester and with three stations, Cambridge, Thetford, and Clacton,
on the 1st January 1975 takes up the position of Director roughly in an equilateral triangle. The particular quasar
of the Royal Greenwich Observatory. studied was 3C 48. This showed nearly 50 per cent
scintillation: The pilot experiment was successful and the
INTERFEROMETRY triangle was extended between Cambridge, Jodrell Bank,
The techniques of interferometry formed the basis of and Malvern.
the work at Cambridge. The first telescopes were simple
interferometers but very soon the phase switched inter- DISCOVERY OF PULSARS
ferometer came into being; the details of this were
published about 1950 by Ryle and Vonberg. It was during the testing of the 18,000 square metre
From the early beginning the resolution obtained by aerial at Cambridge that Jocelyn Bell first noticed the
these methods was better than the single aerial systems. regular pulses. Later observations showed that the regu-
The interferometer developed into a number of varia- larity and accuracy of the pulses was more reliable
tions and gave rise to the more advanced technique of than any clock The team went to great lengths
aperture synthesis for which Cambridge is famous. to establish what these pulses really were and what
Digitation of observations led to a number of advances. mechanism was involved. It became clear that what had
The first aperture synthesis aerials consisted of one been discovered were the playthings of the theoretical
long corner reflector and one movable one about forty astronomers, the neutron stars. This discovery was
feet long. In those days it was quite a sight to see the extremely exciting, opening up as it did new possibilities
small reflector being carried to its new position by the in gravitational physics, the behaviour of very dense
observers and technician. This was followed by a more matter, and the effect on radiation physics.
sophisticated cylindrical parabola driven in attitude by
synchronous motors and the smaller complementary SUPER -SYNTHESIS
aerial fitted to a bogey on a railway system. Here the The reward for enterprise had already been given by
long aerial was set up east and west and the smaller the Science Research Council in approving the setting
one could travel on the rails north and south. up of the 5km aerial with its eight parabolas on the site
of the old railway axed by Beeching. This system of
APERTURE SYNTHESIS aerials went one step further than aperture synthesis.
The technique of aperture synthesis can be described It reached the stage of super -synthesis.
simply as two apertures moving relative to each other The principal task was to be the examination at the
in such a way that they sweep out a narrow ring of large new high level of resolution, of quasars and radio
diameter. The apertures are the aerials and the rotation galaxies. This was an opportunity to resolve some of the
of the earth varies their orientation such that seen problems. In some of the observations there were more
from the sky, one aerial appears ,to trace out an ellipse than two radio clouds associated with the explosions
relative to the other. The interference patterns which that took place. There were also bridge -like links between
are made by superimposing the signals of the two aerials the areas of activity. The radio emission may come from
are then synthesised. From this a chart of the structure the highly charged particles moving at speeds near that
of a source can be deduced. of light and trapped in a tangled magnetic field. They
The next major step was the One Mile Telescope may well be accelerated by the gravitational collapse
which came into operation at the end of 1964. This of groups of stars near the centres of visible galaxies.
was the first complete aperture synthesis purpose-built All these problems and many others should respond
telescope. The sensitivity was extremely high. It was to the high resolution of the 5km telescope. Since 1972
able to detect faint objects near the edge of the observ- the telescope has already shown that its inception was
% able universe. more than justified.
At that time the cosmological debate was in full flow.
The first results from the new telescope showed quite THE MAKING OF HISTORY
clearly that the count of the sources at great distances
(and therefore very old) was less than the number The history of radio astronomy as made at the
required by the "steady state" theory, but consistently Mullard Radio Astronomy Observatory at Cambridge
supported the "big bang" theory. For most of the includes many activities which need a whole volume
theorists this fact, together with discovery of the micro- for description, but the story will go doVin in history
wave background, which appeared universal, marked of the time when two men, mainly responsible for that
the end of support for the "steady state" protagonists. history, were honoured while still making it.

38 Practical Electronics January 1975

 A.."4
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With the Doram catalogue, even

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Doram is an entirely new the part you want within 7days Use the coupon now.
way of buying electronic we'll give you an immediate Send today for the first -ever
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All in all, we're big enough Wellington Road Industrial Estate,
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to offer you stocks of millions of Wellington Bridge, Leeds 1312 2UF. I
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within 7 days from our receipt Doram catalogue for 25p
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We're so confident of our
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Practical Electronics January 1975 39
 With a kit
as complete as this,
all you need add
is a little time.
ALL PRICES INCLUDE V.A.T.
S PIMIDIR BARGAINS ELAC 10in 8 ohm Dual cone 8.50
EMI 13in x 8in 3, 8 or 15 ohm GOODMAN! (ilin 8 ohm Dual
Plain 2.05 cone 2.1.5
With Co -Axial Tweeter
8 ohm only 2.20 FAKE, Tin x 4in, 3 or 8 ohm 1.00
Twin Tweeter 3.70 ADASTRA 10In, 8 or 15 ohm,
Type 350, 8 ohm, 20W 7'50 101V 8.45
Olin, 8 ohm, 10W 2.40
81n, 8 ohm, lOW 2.75 BAKER GROUP 25 121n, 8 or
121n, 8 ohm, 20W 6.70 15 ohm, 25W 745
x 5W 145 P. AP. 0.30
Sin x Sin, Dual cone 8 ohm. Sin, 8 ohm, C/Malf- 045
245 2410, 8 ohm or 64 ohm 0.60 You may have found, from past experience,
ELAC Sin 8 ohm Dual cone 2.25 P. & P. 015
TWEE= AID CROSSOVER Dome Tweeter 8 ohm, 30W 5.40
that your definition of 'complete' is not quite the
EMI S9in, 3 or 8 ohm C/Mag. 1.20
Cone Tweeter 8 or 15 ohm, lOW 2-40
Crossovers CN23 (3 ohm), CN28
(8 ohm), CN216 (16 ohm) 1.20 same as other people's. And your so called complete
Cone Tweeter 8 ohm, 3W 1.45 P. @ P. 0.15
Horn Tweeter 8 ohm, 20W 640 kit comes minus a cabinet, or knobs, or a multitude
KIT FORM CABINETS, TEAK
VENEER. 12in x I2in x 8in with 8in,
13in x rlin cutout
181n x 11in x gin with 13in x
340 of other bits and pieces.
Sin x bin or Olin and 34in
cutout
17in x 10in x Sin with 8in or
2.46
81n cutout for EMI 350 445
P. & P. each 0.45 - That won't happenvvith a Heathkit.
MICROPHONES TW209 5.75 Take our very popular digital alarm
CM70 Planet stick metal, CONDENSER MIKE 600 ohm,
switch crystal
DM160 Dynamic omni-die, ball
1-55 uni.dir
Caasette Stick Mike with R.
086 clock kit. Every part you need will be there, right
metal
UD130 50K/600 ohm, uni-dir,
8.115 Control on/off switch (2.5
and 3.5mm J/Ply) 1.45 down to the solder. And you'll also receive a very
ball metal 5.95 P. & P. 0-20
spare Bib, etc.) 8.80
easy to understand instruction manual that makes
SOLDERING IRONS
ANTEX CN240 15W
SKI Kit (15 watt iron, 2
110 125 25W (low leakage)
P.A P. 0.10
1.90 light work of assembly.
CARTRIDGES AND STYLII SONOTONE 9TAHC or 9TAHC/G
diant. 1.80
In fact all you need are a few
ACOS GP91/25C or 3$1.; Stereo
3509 Stereo ceramic diam.
comp.
0P93/1 or 95/1 Stereo crystal
1.00
145
GOLDRING 0850
I.90
2.90 basic tools and a few enjoyable hours of your time.
0800 3.95
OP94/1 or 96/1 Stereo ceramic 1.75
OP101 Crystal comp. 0.80
0800E
P. & P.
640
0.10
After which you may like to try your hand at
0P104 Stereo ceramic 1.115 D. Diamond Stylii for above
B8R X5M or3XH Crystal comp. 1.70 0800/0850
1.25
1.95 our AR -1214 stereo receiver. Or even a TV.
SX651 or SX0H Crystal comp. 1.90 0800E 395
SC.5M Stereo ceramic 2.60 P. & P. 0 05 And how about an ultrasonic burglar
BATTERY ELIMINATORS output) 6, 7.5 or 9 d.c. output
240V Input 6, 7.5 or 9 300mA 2.95 at 300mA 2.80 alarm disguised as a book?
12V d.c. Input (please specify P. & P. 0.15
TAPES Stud. LP DP PLASTIC LIBRARY CASES
Or, for a bookful of other ideas, just clip the
Sin
51in
50p
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40 Practical Electronics January 1975

 So you've never heard of surface acoustic waves. The second type, the shear wave, vibrates the lattice
Well you soon will. Progress has been astonish- at right angles to the direction in which the wave is
ing in the last five years. Devices have moved from The layers of the lattice slide up and
travelling.
starry eyed physicists' dreams to commercial evalua- down past each other. Again a bulk wave not
tion in electronic systems-a real case of fantasy to found op the crystal surface.
fact. The third type is the S.A.W. (Fig. la). It is a
Imagine you are standing on your favourite holi- combination of the longitudinal and shear waves
day beach looking out to sea; a yacht rocks peace- and is only associated with the surface of a crystal.
fully at the end of the breakwater whilst the waves To tie up the analogy with the waves on the surface
are gently lapping the sand at your feet. You are of the sea, mentioned earlier, it is interesting to note
witnessing the analogy of surface acoustic waves that the motion of a particle travelling in a S.A.W.
(S.A.W.). is also retrograde elliptical (Fig. 1 b).
Transfer the sea waves to the surface of a piece To digress for a moment; bulk waves occur in the
of flat polished crystal and you have S.A.W. Thin familiar, so called, crystal oscillators which are
metal films deposited on the crystal surface enable widely used for highly stable frequency sources in,
the transfer between electrical and S.A.W. energy amongst other things, communications equipment.
to be effected. By manipulating these waves on the It is easy to appreciate early fears that the fric-
crystal surface, oscillators, amplifiers, signal pro- tional forces generated by this mechanical vibration
cessors and delay lines have been constructed. of the crystal lattice would absorb the acoustic wave
energy excessively when the frequency of oscillation
HISTORICAL VIEWPOINT got too high. Fortunately crystals of quartz and
Lord Rayleigh is accredited with the identification lithium niobate have been found to transmit
of the surface acoustic wave. In 1885 he described frequencies from 30MHz to loGHz acceptably.
waves travelling along the earth's surface after an
earthquake, and subsequently a great deal of infor-
mation has been gathered by seismologists.
It was not until the early sixties that the propaga-
tion of high frequency sound waves through a solid
crystal was demonstrated. The development of a
means of conversion between electrical energy and
S.A.W. energy, the Interdigital Transducer (I.D.T.)
in the mid and late sixties, meant that the break-
through had come. S.A.W. exploitation was here.
Surface wave

THE NATURE OF S.A.W.

Surface Acoustic Waves are only one in a family
of wave motions identified in crystalline materials.
The property of all these waves is that of trans-
ferring acoustic energy from one part of the crystal
structure to another.
In crystalline materials the particles are arranged
in an orderly lattice type of structure, each particle
being held in place by an elastic force generated Fig. 1(a). Surface Acoustic Waves distort the
between itself and its neighbours (imagine a lattice crystal lattice as the wave moves along. A
of billiard balls coupled by pieces of rubber band). particle near the surface exhibits retrograde
The longitudinal wave travels through an elastic elliptical motion (b) directly analagousto waves
material by alternately expanding and compressing in water
the crystal lattice. This is definitely a bulk wave not
found on the surface of the crystal.
Practical Electronics January 1975 41
THE SPEED OF S.A.W.
We now come to one of the outstan5ling pro- Magnifwd view of
surface acoustic wan
perties of S.A.W.-the velocity with'which the waves
travel along the crystal is around 105 times slower
than the velocity of electromagnetic waves, i.e. the
velocity of light. In other words an electronic signal Recovered eketrical
signal
that would occupy a cable one mile long could be
contained on the surface of a piece of crystal only
half an inch long. This means that the time taken
for the signal to travel one mile in the cable would
be the same as the time taken for it to travel just
half an inch on the crystal.
It is now possible to glimpse how a delay line of Incoming
electrical
Output transducer

incredible compactness might be constructed. But signal

Crystal substrate
first a means of transferring the electrical signal to Direction of travel of
the surface of the crystal (into a S.A.W.) is needed. Input transducer
surface acoustic wave

Ideally the process should be reversible so that the

electrical signal can be recovered after it has been Fig. 2. A delay line consists of a crystal sub-
delayed. A transducer is required. Fig. 2 shows a strate with transducers separated by a distance
delay line with input and output transducers. depending on the delay required

THE TRANSDUCER
I he transducing action for converting electrical
energy to S.A.W. energy occurs in two parts. The
first stage is a conversion of the incoming electrical
signal to an electrical field which varies in strength
and polarity as the incoming signal.
The second stage takes advantage of the property
of piezo-electric materials to mechanically vibrate
in sympathy with an applied electric field.
As mentioned above, suitable crystals for the trans-
mission of S.A.W. are quartz and lithium niobate,
both of which are also piezo-electric. Thus, all that
is necessary to excite a S.A.W. is to apply a suitable
temporally varying electric field to the piezo-electric
crystal substrate which will also transmit the S.A.W.
This is done using an Interdigital Transducer Fig. 3. An interdigital transducer is used to
(I.D.T.). induce the S.A.W. into the crystal. At the
instance depicted the polarity of the signal and
the lines of force between two points of a finger
THE INTERDIGITAL TRANSDUCER pair are as shown. An alternating electric signal
imagine the fingers of your lett hand interleaved produces an alternating field.
with your right and you have the form of an I.D.T.
This shape is laid down on the crystal substrate as a
thin aluminium film. Width of acoustic
bean
The incoming electrical signal is applied with each
hand (in analogy only of course!) acting as the Thin gold wires bonded to
aluminium transducer
terminals. The electric field will be generated
between the finger of each hand since there will be Output
a time dependent potential between them due to the transducer
electric signal (Fig. 3).
The spacing between each of the fingers is equal Input
transducer
Surf ace acoustic wore
much "gg"rgd
to half the wavelength of the S.A.W. and the width
of the fingers is typically a quarter wavelength. The crystal sabstrate
wavelength is determined from a precise knowledge Black wax
char bar at
of the velocity of the S.A.W. on that particular each end Sec tion.1- Z. through substrate

crystal substrate and the frequency of the incoming Fig. 4(a). Detailed structure of a delay line show-
electrical signal. ing I.D.T.s and wax which absorbs waves so
The aperture of the transducer (see Fig. 3) deter- preventing unwanted reflections from the ends
mines the impedance seen by the incoming electrical of the crystal. (b) shows the delay line in cross
section.
signal and where possible is made to match the line
impedance, e.g. 50 ohms. This typically means an
aperture of 20 to 100 wavelengths. DELAY LINES
The transducer described generates a bi-directional Delay lines are perhaps the most fundamental
S.A.W. The bandwidth of this I.D.T. is inversely S.A.W. devices. Their function is simply to provide
proportional to the number of finger pairs in the a delay between the receipt of a signal and its
transducer (see Fig. 3). The inverse of this same onward transmission, leaving its form unchanged.
process of S.A.W. generation is used to detect They comprise of an I.D.T. at either end of a
S.A.W., i.e. to generate an electrical signal from an crystal substrate. The length of the crystal deter-
incoming S.A.W. mines the delay (see Fig. 4).

42 Practical Electronics January 1975

 Since the I.D.T. is bi-directional, half the S.A.W.
energy is radiated in the wrong direction and if not
stopped would reflect back from the edge of the
crystal thus causing an interfering signal. Thinking
of the sea shore analogy, mentioned above, imagine
the waves hitting the wall of a cliff or promenade
and being reflected back out to sea.
Black wax is used to absorb these unwanted
S.A.W. It is painted on the crystal surface and the
effect can be likened to the sand of the sea shore
which tends to dissipate the waves' energy.
Omni -directional transducers can be constructed
but these have only two thirds the bandwidth of the
bi-directional transducer. The delay possible with
lithium niobate, for instance, is 2.88 microseconds
per centimetre.

FABRICATION Fig. 5. A linearly variable delay line can be

The method of construction is common to most created by having a moveable substrate in
forms of S.A.W. device. Having selected the crystal contact with a fixed substrate
required, cut and polished it, the I.D.T. thin metal
films are deposited using conventional integrated
circuit techniques.
Electrical connection to the I.D.T. is made via
extremely fine gold wires bonded to the metal film.
These wires are typically one to two thousandths of
an inch in diameter.
The formation jof the I.D.T. requires only one
vacuum deposition stage and, once the master mask
defining the areas to be covered with metal is made,
mass production of devices is possible.
Obviously the cost of such a procedure is minimal
and complete standardisation is assured. This com-
patibility with micro -electronic techniques and
promise of inherently economic production are major
reasons for the present flurry of keen commercial Fig. 6. For very long delays a specially prepared
interest. crystal substrate can be used to give a helical
multiple -tap delay line
VARIABLE DELAYS
A variable delay line is clearly now possible using
a multiplicity of output I.D.T.'s to give varying
delays; electronic switching being used to select the Radar dish

delay required.
It can easily be appreciated that just as a wave on
the sea is damped a little by a ship riding on top
of it, so an I.D.T. riding on a S.A.W. will reflect
some of the incident acoustic energy, i.e. attenuate
the ongoing wave. This can give rise to unwanted
signals as they bounce between adjacent I.D.T's. Calibration rungs
generated by S.A.M
Special techniques have been developed to overcome lay lips
these problems.
The variable delay line mentioned will give only
discrete delays and for a linearly variable delay two
crystal substrates are used. From Fig. 5 it will be seen Ph. position Manor

that if the lower substrate is held stationary while

the upper one is moved mechanically, a continuously Fig. 7. A tapped delay line can be used in a radar
variable delay is possible. system to give marker pips on a display screen
An alternative to using longer and longer crystal
substrates to obtain larger delays, and incidentally
the larger the crystal the more difficult it is to
obtain, is to use the helical delay line (Fig. 6).
This is so called because the delay path is a helix, RADAR SYSTEMS
the signal travelling round and round a specially Applications for these types of delay lines include
prepared crystal many times. As can be seen from radar systems. Here the devices would provide
the diagram, transducers are placed along the S.A.W. range calibration and in featureless terrains simulate
path giving many temporally spaced outputs. These a background, i.e. clutter generation. Fig. 7 shows the
outputs can be up to several milliseconds after the simplified block diagram of such a radar range cali-
original input pulse. bration system.
43
Practical Electronics January 1975
 A pulse generated by the r.f. pulse generator is ti-phase coded signal

transmitted via the radar dish to the atmosphere. 0 0

If an object such as a plane is encountered a reflec-

tion of that pulse is returned to the dish some time
later.
The sensitive receiver amplifier then generates a
pulse on the plan position indicator (p.p.i.) the dis-
tance of which, from the centre of the screen,
indicates the distance of the plane from the radar
dish. The r.f. generator also passes a pulse simul-
taneous with the transmitted pulse, to the S.A.W.
delay line. The delay line then gives delayed outputs Input tronsduce Outp t correlating transducer
which correspond, when displayed on the p.p.i., to Surp huts

specific distances from the radar dish. Thus range (a)

calibration of the radar system is achieved.
Magnitude and polarity
of correlating transducer

FILTERS
The bandwidth of the I.D.T. can be closely con-
trolled as mentioned earlier by varying the number
of fingers.
Since the bandwidth is inversely proportional to
the number of finger pairs, a filter, which allows
only a limited range of frequencies through either (b)
side of its designed centre frequency, can be easily
constructed. Fig. 8(a). A S.A.W. correlator may be used for
The centre frequency is determined by the spacing detecting a particular sequence by arranging
between each finger, which is made equal to half the the taps to coincide with the desired signal. A
wavelength of the desired centre frequency. The typical output is shown in (b)
resulting filter is of the bandpass type.
Filters with these characteristics are essential in
every TV and radio, in the i.f. section for instance.
The markets are obviously just right for a simple
mass-produced device which requires no tuning up
after fabrication. Enormous efforts have been turned
in this direction and the complex requirements for a
TV receiver are close to being obtained.

SIGNAL RECOGNITION
Suppose that we require a system whereby a
plane flying around an airport control tower is able
to tell the controller automatically that it wants to (a)
land. Let the plane have a transmitter which gives
out a signal on a particular frequency.
The signal could be coded so that it is unique to
that aircraft. A digital code would be suitable, i.e. a
series of l's and 0's, let these be modulated on the
carrier as a bi-phase coding. This means that the
carrier unchanged represents a 1 and a phase change
of 180° of the carrier is a 0. If the code were four
bits long, e.g. 1001 and two cycles of carrier are
allotted to each bit, then the coded signal would be
as shown in Fig. 8.
How can this signal of known form be recognised
immediately, it occurs notwithstanding the presence
of much interference? Naturally S.A.W. come to our
aid in the form of a tapped delay line or correlator.
The signal is first converted into a S.A.W. by the
input I.D.T. As the signal feeds in it is compressed
in length until it all lies along the substrate.
For simplicity the output I.D.T.s are made up
of single finger pairs called taps. These taps will
give a .maximum output when a or 0 bit of the
1
(b) (G.E.C. Hirst
Research Centre)
S.A.W. appears beneath them, depending to which Fig. 9(a). Photograph of an actual S.A.W.
sum line the fingers are connected (Fig. 8). Thus if correlator which is capable of recognising a
the taps are arranged 1001, as in the diagram, a particular 127 bit sequence. The output trans-
S.A.W. of exactly that form at the correct frequency ducer is inclined to minimise distortion due to
will cause them all to give a maximum output, its length. Photograph (b) shows the large peak
simultaneously, when it appears beneath them. produced when the sequence is recognised
44 Practical Electronics January 1975
 The sum lines add these tap outputs to give a of six finger pairs. Fig. 9b shows the output obtained
large pulse which indicates the signal has been recog- from the large centre transducer, when the coded
nised. Since the S.A.W. signal travels along the sequence is fed into the device. The detection pulse
substrate under the taps it will cause small spurious is easily recognised.
signals before and after it is in the correct position
to cause a large pulse; these are shown in Fig. 8b. CHIRP DETECTION
The photographs show a more ambitious example If instead of bi-phase modulation a pulse of signal
of a tapped delay line (Fig. 9a). It has 127 taps each is used which is rising in frequency with duration,
see Fig. 10. This could be detected by appropriately
spacing the taps on a transducer as shown. The
chirp system is common in radar systems.
A chirp signal- in this case the frequency Increases during the pulse
of the signal AMPLIFIERS
The need for S.A.W. amplifiers is apparent in,
say, a long delay line where attenuation of the wave
chirpngth
by the crystal becomes the limiting factor in the
achievable delay time.
The amplifier to be described makes use of the
electric field generated by the S.A.W., travelling along
a piezo-electric material, by causing it to interact
with electrons travelling through this electric field.
Since the electric field is localised to the surface
riput of the crystal, a conducting medium for the electrons
rensducer
has to be placed very near the surface, yet not
Fig. 10. By varying the spacing between taps as touching, since this would distort the waves. Fig. 11
shown a "chirp" signal can be recognised shows such an amplifier arrangement; a semi-
conductor film is used to conduct the electrons.
If the electrons are moving faster than the S.A.W.
Drift voltage
Amplified energy passes to the wave. Gains of up to 107 times
supply
output
are being achieved at present. These require voltages
of several kilovolts across the semi -conductor film.
It is interesting to note that if the electrons in the
semi -conductor film are travelling slower than the
Silicon diode S.A.W., energy is removed from the S.A.W. and
spacer
the electrons benefit. This property is useful in
absorbing unwanted signals.
OSCILLATORS
The oscillator structure (Fig. 12) combines the
Silicon substrate with
sericonductor film on filter layout mentioned earlier with an external
underside amplifier. This amplifier returns the signal taken
Incoming
signal
from the filter output I.D.T. to the input I.D.T. with
Crystal substrate
an excess of gain. The frequency of oscillation is
determined by the output I.D.T. and the spacing of
the two transducers (D).
The number of finger pairs in the output I.D.T.
Fig. 11. The structure of an amplifier using determines the bandwidth whilst the spacing of the
S.A.W. principles fingers sets the centre frequency. This bandpass
filter then selects one of the many possible frequen-
Amplif
cies of oscillation, which are determined by the
II distance between the input and output I.D.T.s.
The range of frequencies presently possible is
20MHz to 1GHz. Oscillators above 300MHz will
be small enough to fit inside transistor type TO -8
cans complete with their i.c. amplifiers.
Ou put
Applications for these small, cheaply produced
signal oscillators include TV tuners, low noise microwave
sources and strain gauges.
SUMMING UP
It is seldom that one technique can achieve so
much in such a short time. It is easy to see that this
could be an area scheduled for intense activity and
immense growth.
12. A S.A.W. oscillator is produced by
Fig. The combination of minimal power requirements
combining a bandpass filter with an external (or none at all), microminiature construction, cheap
amplifier, the frequency of oscillation being mass production combined with a powerful signal
determined by the spacing between taps on the processing capability must ensure the future of this
S.A.W. crystal branch of technology.
Practical Electronics January 1975 45
FOR SCINTILLATIN

PE
11141 5111111
&
c Eng
SHANFIER
r4 EE

By D. S.
GIBBS

TI is amplifier has been designed on a value for recording. For example, if one wishes to make a
money basis to give the highest standard of recording of a radio programme the input selector
performance compatible with a small case and a is set to "Tuner" and the signal passes through the
components budget of about £30. The result is a input stages and out to the recorder. The signal is
circuit with an output of over 20 + 20 watts into recorded on tape and the tape playback signal
8 ohm loads at less than 0.12 per cent distortion, in appears at the emitter of TR3. By operating S2 one
a case measuring only I4in x 6in x 2in. can then make a direct comparison between the
This has been made possible by the use of a input and the output of the tape recorder.
toroidal mains transformer, by the small size of the The tone control circuit is of the Baxendall type
latest electrolytic capacitors and by the use of the and uses an integrated circuit operational amplifier.
case of the amplifier as a heatsink. The very high gain and large output voltage swing
of this i.c. are advantageous in obtaining very low
PRE -AMPLIFIER distortion and a good dynamic range, whilst the
The circuit of the pre -amplifier is shown in Fig. signal level in this stage is sufficiently high to make
1.1. Here TR I and TR2 form a complementary the noise negligible.
feedback pair. This arrangement has excellent bias The characteristics of the bass and treble controls
stability due to the d.c. feedback through R12. Both are shown in Fig. 1.4. With the tone controls flat
transistors are low noise types and TR( is run at a the circuit has an overall gain of 2 and gives an
bias current of only 150/LA to minimise noise. output of 200mV.
The equalisation components are connected in The scratch filter is a second order type and gives
the feedback loop. R14, R15, C9 and CIO provide an initial slope of 12dB per octave from its 3dB
equalisation for magnetic pickups to within ± 1dB point at 5kHz. The response of the filter and its
of the R.I.A.A. curve, between 20Hz and 20kHz, effect on the treble control is shown in Fig. 1.5.
whilst R 13 and C8 give a flat frequency response
for the tuner and auxiliary inputs. No special MAIN AMPLIFIER
equalisation has been provided for ceramic pickups The main amplifier has a number of interesting
as these seem to be falling out of favour nowadays, features.
but ceramic pickups can be used with the magnetic A long tail pair has been used at the input which
equalisation by connecting passive matching net- increases the loop gain and reduces distortion, but
works of the type shown in Fig. 1.3 inside the more important it provides an accurate ground
record player plinth. reference for the output. The d.c. potential on the
The frequency response of the disc, tuner, and output terminal will normally be less than 50mV
auxiliary inputs is shown graphically in Fig. 1.2. and this will ensure that any d.c. current through
Emitter follower TR3 provides a high input impe- the loudspeaker is of negligible proportions. How-
dance for the tape input and also enables a tape ever, if an output transformer, or a loudspeaker con-
A/ B facility to be provided. This is of particular taining a matching transformer (such as the Quad
value with tape recorders having separate recording electrostatic) is used the d.c. resistance is then very
and playback circuits as it enables one to make a
directXomparison between the signal source and the 'Ferranti Ltd.

46 Practical Electronics January 1975

SPECIFICATION . . .

Continuous Output Power Scratch Filter

-3dB at 5kHz. Slope 12dB per octave
Load Both channels One channel
driven driven Inputs
Disc -3.5mV at 47k S2 RIAA equalised
4 ohms 31-31 watts r.m.s. 44 watts r.m.s. Tuner-I00mV at 100k Q Flat response
8 ohms 23+23 watts r.m.s. 30 watts r.m.s. Aux. -100mV at 100k CI Flat response
15 ohms 17+17 watts r.m.s. 19 watts r.M.S. Tape -100mV at 100k f2 Flat'response

Measured at 1kHz Tape Output

100mV at 4.7k 12 Tape A/B facility
Toneburst Output Power
Load Both channels One channel
Signal to Noise Ratios
driven driven Unweighted figures measured with a bandwidth of
20kHz.
4 ohms 52+52 watts r.m.s. 57 watts r.m.s. Weighted figures follow CCIR C curve. Volume
8 ohms 36+36 watts r.m.s. 42 watts r.m.s. control at max.
15 ohms 21+21 watts r.m.s. 22 watts r.m.s. Tuner, Aux. Unweighted -68dB,
Weighted -72dB
Measured with a I kHz tone burst of 8 cycles on and Disc. Unweighted -62dB,
512 cycles off. Weighted -76dB
Tape Unweighted -76dB,
Distortion Weighted -82dB
(Figures are relative to an output of 20 watts into
15 ohm load-Less than 0.1 per cent at any power
8 ohms)
level up to 15 watts between 100Hz
MAIN AMPLIFIER ONLY f Unweighted -96dB
and 10kHz. Less than 0.02 per cent
below I watt output. (volume control at min.) Weighted -100dB
8 ohm load-Less than 0.12 per cent at any power
level up to 20 watts between 100Hz Balance Control
and 10kHz. Less than 0.02 per cent Full rotation cuts off either channel
below I watt output.
4 ohm load-Less than 0.5 per cent at any power Dynamic Range
level up to 30 watts between 100Hz
Disc input at I kHz =32dB (i.e. input of 150mV)
and 10kHz. Less than 0.05 per cent
below I watt output. Interchannel Crosstalk
Frequency Response -50dB
-1dB at 28Hz and 15kHz
Tuner and Aux. inputs{ -3dB at 17Hz and 30kHz Stability
-IdB at 25Hz and 30kHz Unconditionally stable. Will drive electrostatic
Tape input{ -3dB at 14Hz and 60kHz loudspeakers
Disc input-Within I dB of the RIAA curve between
20Hz and 20kHz Output Impedance
Less than 0.1 ohms
Tone Control
Bass ± I 2dB at 100Hz, 18dB at 30Hz Dimensions
Treble + 12dB at 10kHz, f I6dB at 20kHz 14 x 6 x 2 in.

much lower than the speaker impedance and it speaker coupling capacitor is used, the reactance of
is advisable to connect a resistor of about 0.5 ohms this capacitor starts to become appreciable at low
in series with the output of the amplifier. frequencies just when the most damping is required.
This will reduce the output power by a few per The d.c. coupled output is made possible by the use
cent but will minimise the d.c. current. In practice of balanced positive and negative supply rails, and
the resistance of the_ speaker leads will often be these also assist in obtainin clean symmetrical
sufficient to provide the 0.5 ohm required. limiting under all load conditions.
The d.c. coupled output ensures that the speaker The constant current source TR8 helps in obtain-
damping is maintained right down to d.c. giving a ing low crossover distortion by providing a rapid
clean solid bass response. Normally, when a transition of drive current between the two output
47
Practical Electronics January 1975
 TO LIH CHANNEL

R9 R26 10k fi
C3-* r--1
47611
lo C6
150pF

.r"'F TAPE

TR2 0/P I/P R27

3960 VR2
1AUX1
10060
SKI RI
TX
213 C12 R24 2.2k11 ITREBLEI
113 00k 1.1 1Min1pF
TR1 C16 C18
K2 R3 S1 A R5 C11

Z7X 239
F
150 0 pF 22pF
lOokri lka 10pF 1 kfL
7UNERI 812 47060 [TAPE'
ZTX 239

SK3
1()ISCI CO
C
10611 6800 475
10)JF SIB pF !FILTER]
R4 R6
4-760 47kfl von RI3 R15
10k0 475
47060 22
aim [MONO'
C2

470pF
33 F

R2 R8
10060 220 kit

508F )5on

TO L /H CHANNEL

COMPONENTS . . . Capacitors
Resistors C1, C101 1i).F 35V tantalum
R1, R101 10010.2 R25, R125 10k12 C2, C102 331.1.F 16V elect.
R2, R102 4.7ki2 R26, R126 10652 C3* 15011F 16V elect.
R3, R103 100k22 R27, R127 39kS2 C4* 150p.F 16V elect.
R4, R104 4.7ki2 R28, R128 4-7ki-2 C5, C105 101.i.F 25V tantalum
R5, R105 1kS2 R29, R129 4.71a2 C6, C106 3311F 16V elect.
R6, R106 47k0 R30, R130 221a2 C7, C107 22pF 160V polystyrene
R7, R107 47052 R31, R131 1k1-2 C8, C108 470pF 160V polystyrene
R8, R108 100ki2 R32, R132 2.2k12 C9, C109 6,800pF 400V polyester
R9, R109 47ki2 R33* 47022 1W C10, C110 .0221/F 160V polyester
R10, R110 1.5k12 R34* 47052 1W C11, C111 1012.F 25V tantalum
R11, R111 4.7ki2 R35, R135 100k12 C12, C112 11.i.F 35V tantalum
R12, R112 470ki2 R36, R136 1k0 C13, C113 101.1.F 25V tantalum
R13, R113 101(12 R37, R137 22652 C14, C114 101.1.F 25V tantalum
R14, R114 10kI2 R38, R138 4.71a2 C15, C115 .0221J.F 160V polyester
R15, R115 470ki2 R39, R139 3.3k52 C16, C116 1,500pF 160V polystyrene
R16, R116 220kf2 R40, R140 1-2k0 C17, C117 1,500pF 160V polystyrene
R17" 150i2 R41, R141 100652 C18, C118 22pF 160V polystyrene
R18* 1500 R42, R142 4.7k0 C19, C119 4,700pF 400V polyester
R19, R119 4.7kS2 R43, R143 100t2 C20, C120 4,700pF 400V polyester
R20, R120 100kS2 R44, R144 15k0 C21, C121 1011F 25V tantalum
R21, R121 1ki2 R45, R145 1kS2 C22* 0.112.F 30V disc
R22, R122 10k22 R46, R146 0330 2.5W C23* 0.11,.F 30V disc
R23, R123 220kS2 R47, R147 0330 2.5W C24* 4701.1.F 25V elect.
R24, R124 2-2k0 R48, R148 100 1W C25* 470i).F 25V elect.
All IW 5% carbon film unless otherwise rated C26, C126 1i/F 35V tantalum
Note: R17*, R18*, R33* and R34* are common C27, C127 101.LF 25V elect.
to both channels; similarly for all other C28, C128 22pF 160V polystyrene
components asterisked C29, C129 33pF 160V polystyrene
C30, C130 -1;1F 250V polyester
Potentiometers C31, C131 22;1F 63V elect.
VR1, VR101 100ki2 twin gang linear law (RS) C32, C132 22i1F 63V elect.
VR2, VR102 1001a2 twin gang linear law (RS) C33, C133 .1;.).F 250V polyester
VR3. VR103 10ki2 twin gang log law (RS) C34* 3,400+3,400µF 40V elect.
VR4* 251a2 single gang linear law (RS) C35* 3,400-r 3,400µF 40V elect.
VR5, VR105 1ki2 skeleton preset (RS) C36* .011.1.F 750V disc

48
Practical Electronics January 1975
 TO L/H CHANNEL

-115V R33*
30V

470 n

KS150B
C24*
4700E
R38
4 760
D3
2C231FF 0;
04 IF
ZS170
R43
0011
TRY

KS120B R42
R37 BD 699
R29 2260 BFS98
4 7kfl
4.7611

R46
0 330
22 pF
TR4 TR5
C21 R1

ZTX 100kfl SK
10uF 213 ZTX
213 844
R36
R30 1.5k 11 i10R48
1kfl TR7 R47
22kfl [VOLUME] 11.
C30 0-3311
0 1VF OUTPUT
VR3 C26 VR5
R32 611 R45
'Oka C27 '10EF ZTX C33
/ 22k11
108 TRIO F
1k11

Y
4_VR 4 2560 835
C29
33pF
TR6
060700 °-C SK6

.1.331 100611
939 840
pal I BALANCE
336 1 2611
BFS61

-15V 30V
D2 C32.
EARTH KS150B ITC25* 22uF
470AF

0-0
D7
09 C 34*
3400pF
3400,uF 40V

D6
D6
Fig. 1.1. Circuit
of right-hand MAINS
INPUT 0-0 D6-9= ZS 271 0
channel pre -amplifier, main
amplifier and common power C350 momm
supply. Left hand channel is 3600uF.340y3v
identical
POWER SUPPLY

Semiconductors Switches
Recommended type Alternatives S1A, S1B, S101A, S101B 4 -pole 3 -way rotary
TR1, TR101 ZTX239 Ferranti ZTX384, ZTX109C (Lorlin)
TR2, TR102 ZTX213 Ferranti ZTX214, ZTX530, S2, S102 2 -pole changeover pushbutton (RS)
ZTX502 S3* 2 -pole changeover pushbutton (RS)
TR3, TR103 ZTX239 Ferranti ZTX384, ZTX109C S4, S104 2 -pole changeover pushbutton (RS)
TR4, TR104 ZTX213 Ferranti ZTX214, ZTX502, S5 D.p.s.t. rotary mains switch (RS)
ZTX531
TR5, TR105 ZTX213 Ferranti ZTX214, ZTX502,
ZTX531
TR6, TR106 BFS61 Ferranti ZTX451 Miscellaneous
TR7, TR107 ZTX108 Ferranti ZTX238, ZTX239, T1 Gardners mains transformer type SL8, 20.5-0-
ZTX109 20-5 volts
TRB, TR108 BFS98 Ferranti ZTX551 LP1 Neon panel lamp with internal resistor
TR9, TR109 BD699 Motorola BD699A Case-H.M. Electronics type GB3
TR110, TR110 BD700 Motorola BD700A Stereo jack socket, 4 -DIN 5 way sockets, four
D1*, D2* KS150B Ferranti KS150A 4mm sockets, five control knobs, three push-
D3, D103 KS120B Ferranti KS120A button switch buttons (RS), two Eagle 20mm
D4, D104 ZS170 Ferranti Any ZS170/270 fuseholders, 1A fuse, 2A fuse, four Lektrokit
series diode spring clips type LK2791 (1.5in), five way tag -
D5, D105 ZS170 Ferranti Any ZS170/270 strip. screws, spacers, grommets, aluminium
series diode angle, connecting wire.
D6*, D7*, D8*, D9* ZS271 A glass fibre printed circuit board printed with
Ferranti ZS272, ZS274, component locations, and a kit of semiconductor
ZS276 or ZS278 devices for this project are available from Davian
ICI, IC101 UA748CV Signetics Texas SN72748P Electronics, PO Box 38, Oldham, Lancs.

Practical Electronics January 1975 49

transistors. Bias transistor TR7 operates in the
"amplified diode" mode and is thermally coupled to 47
the output transistors by being clamped to the heat - SC Ceramic
Pickup
Disc
input
sink. This gives a great improvement in bias stability of Disc
as any increase .in heatsink temperature is com- Ce amic
Pickup
Ireamp Ceramic
input
Disc 56 Op F of
pensated for by a reduction in bias. 27 input 22 0.01
Pickup 10 Pr camp
kIl Preamp kIl pF k.a

OUTPUT TRANSISTORS
The output transistors TR9, TRIO on the circuit Ve; (a) (b) (c)
diagram are shown as single transistors for simpli-
city, but they are in fact monolithic Darlington pairs
with a minimum current gain of 750 at 3 amps.
These transistors have proven themselves to be elec- Fig. 1.3 (a). Circuit giving approximate matching
trically very robust and we have found that a 2 amp for most types of ceramic pick-up ; (b) circuit for
fuse in the positive rail 'is adequate to protect them matching the Decca Deram ceramic pick-up;
against short circuits on the output. (c) circuit for matching the Sonotone 9TAHC
ceramic pick-up
Note that the fuse should be connected in the
positive rail and not the negative rail. When the
positive supply is removed the whole main amplifier
is turned off because the bias is removed from the
constant current source TR8, and also from the
input stage TR4 and TR5. This in turn turns off
T R6.
POWER SUPPLIES
When one is designing a small, low cost amplifier
the first refinement that one has to do without is the
use of a stabilised power supply. This introduces a
Belem+
Output dB
number of problems; but there are compensating
+2 0 ,..- -... advantages.
+1 5
%.... DISC INPUT
The problems arise because of the lack of stabili-
sation. To get 20 watts output into an 8 ohm
o

0 R ICM UXILIARY INPUTS

'N
\ speaker we need a power supply which will deliver
45 volts on load. But when the amplifier is not
giving any output and there is only a light load
io
N on the power supply, its voltage can easily rise to
I5
%N.. 60V. If we allow for mains voltage variations, then
In 1110 1000
Frequency He
MOO
under the worst conditions the supply voltage could
(C) reach nearly 70V. With a stabilised power supply
output transistors rated at 50V would have been
Fig. 1.2. Frequency response of disc, tuner and satisfactory, but with our unregulated supply we
aux inputs need output transistors which will stand at least 70V.
Not only this but all the electrolytic capacitors need
to be conservatively rated as well.
--...... 1452_ TREBLE
The unregulated power supply does however have
+15 ....
',... MAX BASS ..
.., one very great advantage. A musical signal has a
+10
., low average power level with occasional peaks of
+5
0
CONTROLS FIAT
...`,
***,
......:R.NRR 'C..
..* high power. For a short period (until the power
.. --'------s . supply voltage drops).an amplifier with an unregu-
.." lated supply can deliver a power output very much
greater than its continuous rating. This amplifier
1

..../. MIN SASS

-1
-20 ......
., ..21IN TREBLE
will deliver 23 watts per channel continuously into
100 1000
8 ohms, but on a musical signal it is almost as
1

Greg envy He
(c) good as a 35 watt amplifier.
Fig. 1.4. Frequency response of the tone Lastly it might be as well to clear up exactly what
controls we mean by continuous power. With 15 ohm loads
the power dissipation is sufficiently low for the
RCM ye
amplifier to be run at full sinewave power con-
Outp t dB tinuously. With 8 ohm loads it will also safely run
.5
0
continuously provided that it is placed in a well
ventilated position where air can circulate freely
\
, ...Ss.
5
11r4:.
10
',..,MAXTREBLE
around it, but the back of the amplifier tends to
15
MIN TREBLE \
become rather hot after about 30 minutes of full
20
\ FLAT TREBLE
sinewave power. With 4 ohm loads the amplifier
25 should not be run at full sinewave power for more
50 than about 10 minutes at a time, or the temperature
m 100 1000 13000 of the output transistors may become excessive.
Frequency Hz

(b)
One does not normally listen to sinewaves of
course and with a normal music or speech input
Fig. 1.5. Frequency response of the scratch the amplifier can be run continuously at full volume
filter without any reservations.
SII Practical Electronics January 1975
DISTORTION Catortio

At full output the distortion introduced by the NO

other components in the hi-fi system will be much

greater than that of any reasonable amplifier. Mov- o011
ing coil loudspeakers can generate up to 10 per I

cent distortion and even electrostatic types can give

tuner can
I

0.5 per cent. A good modern f.m. 006

Istitr dips at
generate 0:5 per cent., a tape recorder about 2 per
cent, and a gramophone pickup can reach as much 004
as 20 per cent on the inner grooves. Compared to
these figures the performance of all but the most 10111I

mediocre amplifiers is adequate at full output. 0 02

There lies the snag. All the signal sources may ......... Ulla

have considerable distortion at full output, but the o

10 000
distortion falls rapidly at lower levels. This is not
001
04100 Pow., (watts)

necessarily the case with an amplifier. If crossover

distortion is present the distortion may be only 0.1 Fig. 1.6. Distortion against output power for
15 ohms measured at 1 and 10kHz
per cent at full output but may easily rise to per1

cent or more at low levels. Crossover distortion is

particularly unpleasant because it generates high
order harmonics, which are discordant and easily
perceived. 014
For crossover distortion to be negligible it should
be less than 01 per cent at all power levels. Low U.2
order harmonic distortion is less objectionable and I

up to 0.5 per cent can be tolerated. So we can say

that our amplifier should have a distortion specifica- 010

tion of no worse than 0.5 per cent at full output,

and below 0.1 per cent at all power levels below 06 I

1 watt.
The use of a constant current source in this ampli-
fier has helped us to achieve a very low level of 106

crossover distortion-typically about 0.01 per cent at 10 110

1 watt-and with 8 or 15 ohm loads the harmonic 02

distortion is below about 01 per cent at all power lAnaplifla clip at

123.6-01

levels up to full output. With 4 ohm loads the /1)2

1

performance does not reach quite the same standard, IltYla

but it is still below 0.1 per cent at watt and 0.5

1
o
it

per cent at full output. 001 01 10

POIRr (Nth)
10

Fig. 1.7. Distortion against output power for

FREQUENCY RESPONSE 8 ohms measured at 1 and 10kHz
Many constructors are firmly convinced that a very Dmlortion
extended frequency response is a good thing. This ra
1

is a complete fallacy because - I

i
i

1. Human hearing extends from about 20Hz to a

20kHz at the best. There is some evidence that

transients containing harmonic components 4

above 20kHz can be distinguished but there is

certainly nothing to be gained by extending the 10klit

response past 40-50kHz. Atriplittar

clips at

2. There are very few loudspeakers with any 31 watt,

useful response below 30Hz or above 20kHz. 1141z

3. There are no radio signals with any audio 10 100

above 15kHz. O 0t 01
Output Pow. (watts)

4. There are no records or cassettes with any Fig. 1.8. Distortion against output power for
audio above 20kHz. 4 ohms measured at 1 and 10kHz
speaker cone to flutter violently. If the h.f.
In fact the only audio signal available which response is very extended then h.f. noise and multi-
might have anything above 20kHz would be a very plex sideband components can intermodulate with
high quality tape recording of a live performance. each other and with h.f. audio signals to produce
A very extended frequency response can be a audible distortion and noise. So what is the ideal
very bad thing. If the low frequency response is very response? Probably something like 20Hz to 50kHz
extended then low frequency noise from turntable ± 3dB.
rumble, warped or off centre records, or tape record- This amplifier has been designed so that the
ings can get through the system and cause the frequency response falls rapidly below 10Hz, and so
Practical Electronics January 1975 51
 Fig. 1.9. Output waveform of the
amplifier when slightly overdriven
with a 1kHz sinewave showing the
clean symmetrical limiting with free-
dom from latch -up
Fig. 1.10 (a). 1kHz square wave re-
sponse with 13I-1 resistive load; (b)
10kHz square wave response with
VI resistive load; (c) 10kHz square
wave response with load of 811 and
0.1pF; (d) 10kHz square wave
response with a load of tin and 2µF

R49
Right
Output Headphone
Output Jack
a separate rumble filter is not necessary. The h.f.
response of the tape input extends to 50kHz but
iiatrtt
the radio input has been restricted to 30kHz to
attenuate multiplex and carrier components. With
the scratch filter switched in all the inputs are 3dB
Left down at 5kHz.
Output
47011.1W
TRANSIENT RESPONSE
For good reproduction it is essential that the
Fig. 1.11. Headphone attenuator circuit if re- amplifier should have a good transient response
quired. Note that resistors have been omitted with as little ringing as possible, even when fed into
from Components List a highly reactive load such as an electrostatic loud-
speaker.
FROM C21
In this amplifier a particular effort has been made
TO TR4 BASE
to achieve a good transient response and Fig. 1.10
shows the performance of the amplifier under various
load conditions. Note that with a 2µF capacitive
load the ringing is of very low amplitude and soon
dies away. If a 0.5 ohm resistor is connected in series
with a 2/AF load (as we recommended for the Quad
speaker), then even this small amount of ringing is
completely eradicated.
QUADRAPHONICS
No special provision has been made for quadra-
phonics in the prototype, mainly because of lack of
space, but it is a simple matter for the enthusiast
to adapt the circuit for use with a quadraphonic
decoder.
All that is necessary is to break the connection
PRE -AMPLIFIER I OUTPUT TO QUADRAPHONIC IMAIN AMP between the preamplifier and the main amplifier and
FROM CI21
DECODER
replace it with a switch and a DIN input socket, as
shown in Fig. 1.12. The two front channels can
Fig. 1.12. Connections for quadraphonic decoder. then be fed back into the Orion main amplifiers
DIN socket connections are as follows: - whilst the back channels are fed to another ampli-
1. Left channel front input from decoder fier. An additional pair of Orion main amplifiers
2. Earth would be ideal for this purpOse.
3. Left channel output to decoder
4. Right channel front input from decoder Next month: Constructional details and setting
5. Right channel output to decoder up.
5' Practical Electronics January 1975
RE -READING one of the earliest and equally artless. Both came
publications on electronic music together, however, in considering
recently I came across the following their respective tape compositions
statement made by Herbert Eimert, to be one-off, once -and -for -all per-
founder of the Cologne Radio formances.
Electronic Music Studio:
" That-electronic music cannot be
performed on instruments is due to the Live electronics
fact that the number of individual sound So Eimert was right. Given the
elements is so great that any attempt to complexity of a totally serial com-
find means of instrumental realisation is position with its rapidly changing
doomed to failure."
rhythmic, pitch, spatial, dynamic
One's immediate reaction is to and timbre elements, only a taped
wonder whether he would have sequence could do justice to a
ventured to say this now, in the age of particular concept. No amount of
the synthesiser, when many pop juggling around with electronic
groups have some kind of synthesiser. organs and peripheral sound effect
Perhaps even twenty -odd years units would reproduce on the con-
ago, when Eimert's article was cert platform what could be realised
written, there was little excuse for on tape.
such a statement; the electronic The same applies to Schaeffer's
and electrophonic instrumental field collages, where natural sounds,
was by then quite sophisticated. A recorded wherever they existed, were
little relatively recent history may be processed electronically, the result
pulled in here to support, or maybe defying any musical instruments-
excuse, his apparently negative save perhaps the Melotron, which is
remark. nothing more than a filing cabinet of
tape recordings with a piano key-
board attached. Eimert lacks cre-
The Years Between of the musical press. dence in his underlying assumption
It was during this babel of activity that Electronic Music is a style
In the years between the two rather than a medium of expression.
world wars Arnold Schoenberg, that the tape recorder came into
Austrian composer, systematised general use, and with it the very
the 12 notes of the traditional latest in sensational sound, electronic
chromatic scale to produce music music. Anything essentially of an Today's Electronic Music
which did not rely on key (i.e. the acoustic nature was taboo. Needless In today's Electronic Music the
predominance of one note over any to say electronic compositions were factions have largely disappeared;
other) but used all the available meticulously edited and fixed for all Stockhausen has cast off the strait-
pitches equally. Amongst his pupils time on magnetic tape. jacket of total serialisation and in his
was Anton Webern who went a taped works uses the human voice,
stage further than his master; rather gramophone records, short-wave
than treating the 12 notes in a radios and acoustic instruments.
fairly conventional linear manner he Colouristic Effect Schaeffer and his colleagues rely
perfected a style of writing which laid Meanwhile in France there was quite heavily on purely electronic
weight on each individual note as another little sonic revolution taking sound producers.
and when it occurred in the musical place. Whilst those who whored Along with this fusion of two
flow. after strange gods studied the latest differing approaches to taped material
The dynamic levels, pitch and serial techniques in Germany, others came the feeling that performers
timbre were carefully controlled in stayed behind to practice the art of ought to take some share in the
his sparsely written aphoristic instru- colouristic effect for which the French interpretation of this kind of music;
mental and vocal compositions. have always been renowned. hence "Live electronics".
Pierre Schaeffer founded a studio
in Paris dedicated to the study of
the physics and psycho -physics of Pop Sounds
Lionised Webern acoustic phenomena and to the By far the largest purveyors of live
After the war a group of young production, on discs initially, of electronics are the pop groups. (Only
German musicians picked up the musical compositions which took a pedant would argue that their music
almost submerged threads of these raw, natural sounds as their starting is not strictly electronic.) Electronic
revolutionary concepts and made point. Plain aural effect was the instruments work admirably here
Webern their idol. Reinforced by ambition; Schaeffer and his colleague since most of the music performed is
similar pre -organised, or serial, ideas Pierre Henry had little time for the geared to the traditional pattern of
put forward in works by the French intricate number games which the twelve notes to the octave and is old
composer Olivier Messiaen, these Germans were playing. The search fashioned enough to use fairly com-
young intellectuals went on to for "musique concrete" [natural or mon juxtapositions of these notes.
produce a new music in which all non -abstract music] ended with the Above all, pop -music is primarily
the parameters available to music arrival of the tape recorder and the melodic music and this means that a
were fully exploited, almost mathe- simplicity of editing magnetic tape. given instrumental line is unlikely to
matically. The musical results were require rapid changes of timbre.
often impossible to perform by To some extent "serious" live
human beings, yet the European electronic groups have taken a lead
scene rapidly became thick with Partisan Factions from the pop world; the music they
"avant-garde" concerts, many of So electronic music began lite in perform is no more complex to
dubious integrity. two partisan factions: the German - realise than an equivalent piece of
That any worthwhile music has influenced found the French "musique acoustic instrumental music. Should
survived this . period is a minor concrete" positively naive and artless, they require complex arrangements
miracle, given the arrogance of the whilst the French considered the of sound these still have to be pre-
exponents and the loud raspberries Germans inhumanly mathematical recorded on tape.

Practical Electronics January 1975 53

 THE NEXT
DECADE ?
Final selection of readers' predictions

of overlaying the semiconducting layers, creations, having purchased programmes

ARMCHAIR VIEWING assuming there will be enough semi- from the lists in the advertisement
I BELIEVE that in the next decade we conducting material left by tomorrow! pages of his favourite journal, P.E.
could well see many changes in our Soon one may be able to leaf through a Seated at the console of his electronic
everyday life due to electronics. Instead catalogue of "surplus" equipment, which organ, engaged in extempore musical
of travelling to conferences, businessmen at present is described as a technological invention, such will be the interaction
might stay at home and "attend" the breakthrough. Basic techniques could between man and his electronics that the
conference via video and audio links to a soon be outmoded, soldering and the player may well exclaim from the pro-
central conference control, through printed circuit board might soon be fundity of philosophical doubt, "Just who
which they would be able to see and hear replaced by the plug-in module. is playing this machine?" The folly of the
their colleagues. They would also be In conclusion, it could be said that in decade will be an attachment for colour
able to "look up" relevant information the next decade, though there may not TV receivers to permit the display of
through the conference control and have be the advances of the like of the inte- electronically simulated goldfish.
it displayed on their screens for as long grated circuit in the last ten years, D. Letts
as they wish. technology will push its usage to the
We could watch any television (if it limits. Also, present technology will be
could rightly be called this) programme commonplace to the constructor in not
whenever we pleased. so many years.
The printing world can throw away its N. J. Eastaugh
presses, for we will be able to dial
for, say, the front page of today's news- HIGHER QUALITY
paper and have it displayed on our
"newscreens." Yes! even our beloved THE next decade will not unveil any
Practical Electronics will come to us like major electronic breakthroughs but
this. (Don't worry Ed., you will still be MAN AND HIS instead, in a time of financial instability,
manufacturers will concentrate on im-
needed.) ELECTRONICS proving the quality of goods already
No-one will have to think as much,
for we will all have our own computer THE philosophy of electronics in the next available, the risks being too great for a
calculators, and musical instruments
decade is summed up by "digital is large scale venture into something
will be replaced by synthesisers, so that best, and smaller is better". radically new. Maximum profit being
the Pablo Casals' of tomorrow will play Compromised by cost, and using the essential, the fear of failure in a com-
upon streamlined keyboards instead of results of researches into the nature of ponent would be too daunting.
peculiarly shaped pieces of wood. human perception, manufacturers will set Transistors and integrated circuits will
All this sounds rather unlikely? Well, lower standards of sound and image continue to be the main "workbench" of
reproduction. electronics, both on an amateur and
you wait and see.
S. J. Baxendale.
Enthusiasts will reconstruct the professional scale. The valve will still
electronic achievements of the 1920's with command itself a place but will always run
antique components or replicas made by a poor second to the modern semi-
new cottage industries. conductor, as feel it does now.
I

A wide range of games -machines With everybody striving to attract the

designs will be published for the con- prospective customer to their particular
COMMON PLACE structor. At best, they will be war line of components there will inevitably
IN the next ten years no progression is games, or a form of Monopoly in which be many new i.c.s on the market, having
forseeable in the direction of com- the players are relieved of the arithmetic better power handling capacities and
ponent miniaturisation, owing to the of accounting and cannot break the rules. such -like in an effort to better their
impossibility of decreasing pin and The power of present-day mini- predecessors, but none of them will be
encapsulation size. It is likely that more computers will be available in a single fundamentally different.
will be fitted into a single module-Mr. i.c. costing C20, or less. A shortage of raw materials, evident
Shaw's synthesiser on a chip, for example. The military applications of micro- at the present time, will mean price
Specialisation of these circuits is electronics will shock and horrify us, but rises and delivery delays (nothing new!)
almost inevitable, specifications going the constructor will find light relief This could also result in the amalgamation
further and further towards the extreme, from the problems of the day by assembling of many small component retailers who
with fantastic power handling and even the parts of a micro -computerised mouse would otherwise be forced into liquida-
more fantastic frequency ranges, now for his cat to play with. tion by the bigger concerns cornering
only the dream of hi-fi enthusiasts. There will be great interest in the all the custom.
Technology cannot be underrated in generationof special effects. Today's The overall trend will be to encapsulate
sorting out the problems which may Wind and Rain generator will be supple- the components in plastic containers
make these two characteristics (now) mented by tomorrow's Thunder and which constantly seem to diminish in
incompatible. Lightning, the degree of authenticity size.
For the home constructor, today's rising according to ingenuity and the Finally, the high degree of competitive-
high-powered technology may be to- size of purse. ness between manufacturers will result
morrow's workbench experiment. A Electronic musical instruments will have in a higher quality of components-which
home made integrated circuit kit for substantial computer power, and the can only be to the good of the constructor
example; which is not such a far fetched constructor will spend more time in in the end.
idea if one looks at the basic simplicity programming than constructing his M. S. Johnson

54 Practical Electronics January 1975

 A warden who has a receiver on the same
ELECTRONIC LABEL local mains ring is alerted that the caller
DIODES AND ALL
THE present trend of improvement in is in trouble. EXPERIENCE shows that the develop-
electronic technology is likely to A second is the introduction of auto- ment of technology follows some-
provide some new and perhaps exciting mated speed traps, made necessary by thing akin to a log. law curve. In semi-
uses of the circuits as we know them. increasingly restrictive speed limits due conductor technology there has been a
It may be taken for granted that they will to overcrowding and fuel shortages. veritable explosion of new ideas and
reduce in size, become more reliable and These would photograph offenders' cars techniques. If interpolation of this curve
presentable, and who can say how long showing the speed on a print-out. An is attempted then the results can be
they would last. official would collect the photographs somewhat surprising.
The reading of domestic meters by every so often. To avoid the possibility Today's computers using holographic
remote computer, preparation of account, of malfunction causing injustices, offenders or ferrite memory stores are far too
and even automatic payment of the bill would be prosecuted if caught more than cumbersome, slow and expensive. Deve-
by pre -arrangement, is but one aspect. once in a set period of time. lopment of heavy metal organo com-
It is likely that television receivers will The second item, wages, will lead to pounds already well under way should
be used in the dual role of entertainment novel methods of improving reliability bring about the production of high
or access to information, such as avail- of electronic goods. Touch -operated temperature (in excess of 100 K) super-
ability of goods or prices. The telephone integrated circuit sub -systems will replace possibly a
conducting memory stores: -possibly
line perhaps, would be swicchable to a potentiometers and switches, and possibly very primitive forbear of Asimov's
number of facilities, with a "back up" i.c. optical modulators and demodulators positronic brain !

visual display. coupled with optical fibres will replace For constructors, I.s.i. circuits are
One possible change is in the use of plugs and sockets for connecting audio already available, the question remains
pocket, or desk calculators. It is quite discrete units. how large (or small) can they get and for
feasible to envisage these being used as J. de. Rivaz what purpose. Pocket calculators already
mini computers without major circuit have chips containing thousands of active
change. For instance, with a microfilm elements, and rather think that today's
I

attachment, and "access code" operation constructor in ten years will be in much
using the same styled keypad, the film the same boat as those are now who
could be rotated by the command word, lament the passing of the valve, we shall
and illuminated on a slightly enlarged be lamenting the passing of the discrete
screen. transistor.
Finally, how about the "Electronic INTEGRATED LC.'s Looking back, most developments
Label", a microcircuit, so small that it seem to stem from the humble diode, the
could be incorporated into almost any TEN YEARS is not a long time, but I
latest being the ubiquitous I.e.d. so the
article at the manufacturing stage, and believe that man will advance more logical development of this would be the
in the next ten years than in the last
with its own identity calling signal,
came to
"light emitting transistor"-alter the
quiet, unless called by a master beacon. ten. After long consideration I
base bias and "hey presto"; modulated
Nasty though, if you want to go into a the conclusion man's advancement was light output.
pub for a quick one and the wife is of a logarithmic nature and not a linear E. J. Marchant.
looking for you! one. Our greatest advancement will be
A. J. Williams in the field of i.c.s and their inter-
connection.
Soon we will see the inductor being
incorporated in i.c.s and midway through
the decade we will see the key to a new
kind of electronics. No more will i.c.s SIMPLIFICATION
DIGITAL TRACKS be coupled by wires, coupling will be THE following decade, for myself and
THE next decade will be dominated by similar to the lecher lines used in u.h.f. fellow constructors, should bring
political change, which will include tuners. Simply placing the i.c.s one on top simplification in the form of reduced
higher taxation for the individual, and of another, rather like the child's building wiring and soldering for more complicated
wage rates so high that the cost of bricks only in a miniature form. From circuits with increasing use of i.c.s.
maintenance and repair will often exceed this giant leap electronics will virtually With spiralling cost of most products,
the value of the article to be repaired. know no bounds. The solid state power the hope of continued amateur con-
The first item will make it unlikely pack recharging itself from air, light, struction may lie in continued progress
that the colour television boom will be heat, or vibration, for example. in i.c. technology to reduce manu-
repeated with video cassette recording Air and light may be used, as in plants, facturing costs.
or the Ceefax/Oracle system. However, to create chemical changes. These we For the home constructor whose use of
this may well give rise to a new system of can change into electrical energy. Heat i.c.s was exclusively bipolar (TTL), he
video recording towards the end of the given off due to power loss will be may find himself making adjustments
period using digital methods with about channelled back to the power pack to in the not too distant future towards a
150 narrow tracks instead of the helical help recharge power cells. Vibration as different form (CMOS). In this increasing
scan system with its mechanical com- used in self winding watches, used to energy -conscious world, the life of the
plexity. generate power. bipolar form of logic could be drawing
Such a change would be less likely if a These advancements will lead to vast to an end, with less power consuming
large number of helical scan recorders developments, such as the pocket com- logic forms such as CMOS becoming more
were already in use. puter, rather similar to the pocket and more popular.
The lack of money in the hands of calculator we have today, only thousands Amateurs and professionals over the
individualswill be compensated by of times better and incorporating an coming years will be made more power
more in the hands of government, who audio output. conscious and a tendency towards battery
will spend more on electronics. Programme cartridges will also be solid supplies in contrast to more expensive
One possibility taken at random could state, microfilm one small block
as in a.c./d.c. Transformation will be en-
be a distress calling system for old and containing many hundreds of hours of couraged as a practical step for the home
disabled people. The caller presses a information. constructor.
button that activates a device to send Such an instrument would place the Manufacturers will be responsible for
a high frequency signal into the local home constructor almost on a par with this trend, as they become more aware of
mains electricity network. This signal the professional. producing the form of logic which will be
is modulated by a series of pulses repre- Roll on 1984. more financially secure for the future.
senting a number allocated to the caller. A. Tannock. S. Naismlth

Practical Electronics January 1975 55

 Now -two fascinating ways to enjoy saving money!

NEW! Sinclair Scientific kit £19.95

(INC.VAT)

Britain's most original calculator Components for Scientific Kit

now in kit form (illustrated)
The Sinclair Scientific is an altogether 1. Coil
remarkable calculator. 2. LSI chip
It offers logs, trig, and true scientific 3. Interface chips
notation over a 200 -decade range - 4. Case mouldings, with buttons,
features normally found only on windows and light -up
calculators costing around £100 or display in position
5. Printed circuit board
more.
6. Keyboard panel
Yet even ready -built, the Sinclair 7. Electronic components pack
Scientific costs a mere £32.35 (diodes, resistors, capacitors, etc
(including VAT). 8. Battery assembly and on/off switch
And as a kit it costs under £20! 9. Soft carrying wallet
10. Comprehensive instructions for use
Forget slide rules and four -figure Assembly time is about 3 hours.
tables!
With the functions available on the
Scientific keyboard, you can handle
directly Features of the Sinclair Scientific
sin and arcsin, e 12 functions on
cos and arccos, simple keyboard
Basic logs and trig
tan and arctan, functions (and their
automatic squaring and doubling, inverses), all from a key-
board as simple as a
logio,antilogio, giving quick B. 6' 2 9 - I normal arithmetic cal-
access to xv (including square culator's. 'Upper and
and other roots), lower case' operation
means basic arithmetic
plus, of course, addition,subtraction, keys each have two extra
multiplication,division, functions.
and any calculations based on them.
In fact, virtually all complex scientific 1rad 57-295E1°
Scientific notation
Display shows 5 -digit
or mathematical calculations can be In 10 230259
2.71828 mantissa, 2 -digit expo-
handled with ease. Scientific 3.14159 nent, both signable.

So is the Scientific difficult to 0200 -decade range

assemble? 10-99 to 104 99.
No. Powerful though it is, the Sinclair
Scientific is a model of tidy engineering Reverse Polish
logic Post -fixed
All parts are supplied - all you need operators allow chain
provide is a soldering iron and a pair calculations of unlimited
length - eliminate need
of cutters. Complete step-by-step for an = button.
instructions are provided, and our
Service Department will back 25 -hour battery life
you throughout if you've any 4 AAA manganese alka-
queries or problems. , line batteries (e.g.
M N2400) give 25
Of course, we'll happily hours continuous
supply the Scientific or th use. Complete
Cambridge already built, independence
if you prefer - they're from external
still exceptional value. power.
Use the order form.
e Genuinely
pocketable
41/3" x 2-x 1 1/1 6".
Weight 4 oz. Attractively
styled in grey, blue and
Ai white.
56
Practical Electronics January 1975
 Now only
Sinclair Cambridge kit £14.95 (INC. VA'T)

At its new low price, the Components for Cambridge Kit Take advantage of this
original Sinclair Cambridge 1. Coil money -back, no -risk offer today
kit remains unbeatable value. 2. LSI chip The Sinclair Cambridge and Scientific
In less than a year, the 3. Interface chip kits are fully guaranteed. Return either
Cambridge has become 4. Thick film resistor pack kit within 10 days, and we'll refund
Britain's most popular pocket 5. Case mouldings, with buttons, your money without question.
calculator. window and light -up display in All parts are tested and checked before
position despatch -and we guarantee any
It's not surprising. Check the 6. Printed circuit board correctly -assembled calculator for one
features below -then ask 7. Keyboard panel year. (This guarantee also applies to
yourself what other pocket 8. Electronic components pack calculators supplied in built form.)
calculator offers such a (diodes, resistors, capacitors,
powerful package at such a Simply fill in the preferential order
transistor)
reasonable price. form below and slip it in the post today.
9. Battery clips and on/off switch
10. Soft wallet Scientific
Assemblytime is about 3 hours. Price in kit form £19.95 inc. VAT.
Price built £32.35 inc. VAT.
Cambridge
Price in kit form £14.95 inc. VAT.
Features of the Sinclair Cambridge Price built £21.55 inc. VAT.
Uniquely handy package.
41/3"x 2"x11/16",weight31/2oz.
I To : Sinclair Radionics Ltd,
Standard keyboard. FREEPOST St Ives,
3.1415927 All you need for complex calculations. Huntingdon, Cambs. PE174BR
Clear -last -entry feature. Please send me
Sinclair Scientific kit at £19.95
Fully -floating decimal point. Sinclair Scientific built at £32.35
Algebraic logic. Sinclair Cambridge kit at £14.95
Sinclair Cambridge built at £21.55
Four operators (+, x. -:-), with All prices include 8% VAT.
constant on all four.

Powerful constant with separate 'K' *I enclose a cheque for

button. made out to Sinclair Radionics Ltd,
and crossed.
Constant and algebraic logic combine to *Please debit my *Barclaycard/
act as a limited memory, allowing complex
calculations on a calculator costing less Access account. Account number
than £15.

Calculates to 8 significant digits. *Delete as required.

Clear, bright 8 -digit display. Signed
Operates for weeks on four AAA Name
batteries.
Addiess

Please print. FREEPOST-no stamp I

Leeded. PE/1/75

Sinclair
Sinclair Radionics Ltd,
FREEPOST St. Ives,
Huntingdon, Cambs. PE174BR.
''''''''''''''''''' Reg. No: 699483 England. VAT Reg. No: 213 8170 88.

Practical Electronics January 1975 57

PE
III III NI III
By D. SHAW

PART THREE
Keyboard Controller
Noise Generator
Ring Modulator
Power Amplifiers

THIS month the remainder of the electronic a series of consecutive key contacts, then VRI may
circuitry in the synthesiser is described which be adjusted over a wide range without affecting the
includes KEYBOARD CONTROLLER, RING MODULATOR, "tune" of the vco's.
NOISE GENERATOR and POWER AMPLIFIERS. In simple terms the "position" of the two -octave
keyboard may be varied over the audio frequency
range and the "white" notes may be made to play
THE KEYBOARD CONTROLLER in any required key signature. This latter feature will
The KEYBOARD CONTROLLER as illustrated in Fig. commend itself to those "play -it -by -ear" musicians
3.1 is a relatively simple means of providing a range who may sometimes find difficulty in translating a
of voltages which, when applied to the input of a well known melody in the key of C into its correct
vco, cause it to oscillate over a range of pitches signature.
normally associated with a chromatic scale or, For more serious applications, however, the ability
alternatively, over a range of pitches quite outside to swing the keyboard "position" enables the Mini -
what might be termed normal musical acceptance. sonic to play in tune with a number of conventional
ICI and 1C2 are inverting operational amplifiers acoustic instruments which may, themselves, not be
whose outputs are linked by a chain of resistors the precisely "spot-on" as far as tuning is concerned.
junctions between which are connected to the key-
board contacts. R5 and VRI form a divider between KEYBOARD RESISTOR CHAIN
the positive rail and ground such that the swing of No setting -up is required for the KEYBOARD CON-
the potentiometer covers a range of about 4.7 volts. TROLLER other than to check that the outputs of both
The wiper of VRI is linked to both i.c.'s so that ICI and IC2 respond correctly to the settings of VRI
the output of these devices will track, in unison, the and VR2. Fig. 3.1 gives a table of resistor values
setting of VRI . RI and VR2 form a second divider which may be used for the divider system on key-
between the negative rail and ground with the wiper boards of various sizes.
linked to ICI only. Thus VR2 is able to provide an It will be noted that the overall value of resistance
offset to ICI which is variable over 4.5 volts. in each case is approximately the same in order that
The purpose of the voltage difference between the the loading on the i.c.'s will vary by a minimum
swings of the two potentiometers, is so that, under amount regardless of the size of keyboard employed.
normal conditions, the key contact voltages can never
go positive and thus drive the vco's into saturation. THE "HOLD" OR ANALOGUE MEMORY
Although covered by the general heading of KEY-
SPAN AND TUNE CONTROLS BOARD CONTROLLER the HOLD circuit is a quite
The KEYBOARD CONTROLLER can be matched to a separate entity which fulfils an important function
wide range of keyboard sizes and vco control in the scheme of the synthesiser.
voltages. Last month it was indicated that the ENVELOPE
lf, for example, a two octave keyboard is to be SHAPER could give a decay characteristic lasting up
used and the required control voltage for the vco's to 16 seconds. In other words, from the instant the
is 600mV per octave, then VR2 (the "Span" control) key contact is broken, the audio signal will continue
will require to be offset by 1.2V with respect to the -at a diminishing level-for the prescribed period.
inverted value of VRI's setting. Once this has been It is obvious therefore that, for the best effect to
used and the required control voltage for the vco's be achieved, the vco frequency must remain constant
are able to reproduce a chromatic octave by making for the period over which the decay is taking place.

58 Practical Electronics January 1975

 With the key contact broken so too is the vco COMPONENTS .
programming voltage disconnected unless there is
some means by which the vco can continue to be
programmed regardless of key contact condition. The
HOLD circuit provides the means whereby the vco KEYBOARD CONTROLLER
AND HOLD
can continue to oscillate at the frequency prescribed
by the last programmed voltage either until the Resistors
ENVELOPE SHAPER completes its cycle or until another R1 100
voltage is programmed in. R2 -R4 470 (3 off)
R5 9.1 kit
HOLD CIRCUIT R6, R7 470 (2 off)
R8, R9 200 (2 off)
The circuit of the HOLD facility is shown in Fig. R10 470
3.2a. IC3 is an operational amplifier in which the R11 et seq See text
output signal is divided by means of VR4, R8 and
R9 to provide balanced levels of positive and nega- Potentiometers
tive feedback. VR1, VR2 100 linear carbon (2 off)
When the balancing is carefully done the circuit VR3 100 sub -miniature horizontal
is theoretically capable of presenting an infinite skeleton preset
VR4 100 15 -turn preset
impedance to incoming signals. In practice, however,
it is more usual to calculate the input impedance on Capacitors
the basis of the parallel value of the feedback C1 1,000pF
resistors times the open loop gain of the amplifier. C2 1pF 63V polycarbonate
Thus the input impedance is of the order of 2,500
megohms. Integrated Circuits
The hold capacitor (C2) is, ideally, a low leakage IC1-1C3 Type 741 8 -pin d.i.l. (3 off)
type. A charge applied to C2 is reflected at the out-
put of IC3 with any drift at the output due to a Miscellaneous
combination of capacitor leakage and minor thermal SK1 2mm socket
effects within the i.c.

KEYBOARD CONTROLLER

-9V

471a1
R3

47k11

RN R12 (see table)

Keyboard contacts

Fig. 3.1. Circuit of the KEYBOARD CONTROLLER (excluding the HOLD circuit). The table (below) shows
values of resistors (R11 et seq) and numbers required for various length keyboards. This applies to both
printed circuit and conventional keyboards

KBD DIVIDER RESISTORS

Size Resistor Number off

Stylus or Control
1 octave 1500 13
Pin I on DIN SKT
2 octave 820 25
3 octave 51 or 560 37
4 octave 39 or 430 49 Fig. 3.2(a). The circuit of the HOLD section of the
5 octave 33 or 3652 61 KEYBOARD CONTROLLER. (b) It is important that
this circuit should be adopted when nulling the
HOLD offset. Temporary links are shown dashed.
The feedback resistor should be 10N1c2 or more

Practical Electronics January 1975 59

 It is possible to balance the circuit such that the STYLUS
output drift is better than I mV /sec but to do so In the first prototype the stylus employed two con-
requires considerable patience and care, particularly tacts and was illustrated on the front cover of the
when nulling the offset. The circuit for this latter November issue. The double contact, however,
procedure is shown in Fig. 3.2b. The component greatly added to the difficulties of playing the instru-
assembly should be as shown on the circuit board ment and thus modifications were carried out so
layout but the wiper of VR4, instead of being that a single contact stylus could be employed.
linked direct to the output of IC3, is temporarily Perhaps the simplest stylus involves the adaptation
connected to the OV rail. of a ball-point pen (see Fig. 3.3b). If this method is
A second temporary feature is the inclusion of a chosen it is important that all traces of ink are
high value feedback resistor (ideally 10M12 or more) removed from the ball end using an organic solvent
as shown hatched in Fig. 3.2b. before any attempt is made to solder in the wire
Adjust VR4 so that its wiper is close to the centre lead.
of travel and, with power on, adjust VR3 until the
output of IC3 is precisely zero volts. The temporary Remove ink residue using
links and feedback resistor may now be removed organic solvent
and the circuit completed as shown in Fig. 3.2a.
Minimising the drift in the HOLD circuit is best
done by ear, i.e. using the Minisonic vco's rather Ink tube
than an oscilloscope as part of the test equipment. Stylus lead soldered into'nib'
Details of this procedure will be included as part of
the final setting up.
Fig. 3.3(b). A suggested construction method for the
stylus using an old ball-point pen

To KBD Note that organic solvents should be treated with

Controller
caution since most of them give off a vapour which
etc to
can be harmful if inhaled continuously. The
3 octaves
assembly when completed should be potted within
the lower half of the pen by means of Araldite or
Silicon Rubber Compound.
Those constructors having access to a lathe could
Fig. 3.3(a). Wiring of the edge connector strip as used make up a stylus from a piece of lin brass rod. If
on the prototype. Resistors are wired in from the con- this method is used it is important that the extreme
ductor side of the board. Excess wire on the other tip of the stylus should be rounded off and well
side of the p.c.b. should be trimmed off and filed polished to ensure a good contact.
flush so that the board may be glued to the front
panel
ULTRASONIC TRIGGER SYSTEM
THE KEYBOARD (The circuitry in this section is the subject of a Patent Application)
The Minisonic offers the possibility of being The changeover from a double -contact to a single -
operated with a number of keyboard options, the contact stylus presented a difficult problem simply
cheapest being the edge -connector type. Other because the signals required to set the HOLD circuit
options will be discussed next month. and to trigger the ENVELOPE SHAPERS are essentially
A printed circuit keyboard was adopted in order incompatible. Direct coupling between the inputs of
that the instrument could be both compact and fully these two circuits was therefore not possible since,
self-contained. In the prototype a three -octave key- once the HOLD capacitor was charged, the d.c. level
board was made up using a standard edge -connector would remain on the stylus lead and the ENVELOPE
strip as shown in Fig. 3.3a but satisfactory operation SHAPER in the "on" condition, until the charge on
could only be achieved after much practice due to the HOLD capacitor had leaked away.
the narrow conductors involved. Mounting of the This would occur quite rapidly in the circum-
divider resistors should be generally as shown in the stances thereby giving rise to an undesired porta-
diagram. mento effect. Similarly it was not possible to de -
couple the ENVELOPE SHAPER from the stylus lead
since so doing would restrict the "attack" phase to
COMPONENTS . . . one rate only-and that very fast. The solution
proved to be the application of a principle which
HARDWARE is believed to be unique in electronic musical
instruments.
Control Knobs, 14mm-19 with skirt, without 1

skirt (ReAn Products-see Market Place) HF OSCILLATOR

On/off d.p.d.t. toggle
Battery connectors, PP9 2 -off positive and nega- A HIGH FREQUENCY OSCILLATOR is coupled directly
tive into the KBD CONTROLLER in such a way as to dis-
Olin matrix Veroboard 45 x 34 holes tribute the signal evenly across the divider. The
Keyboard 37 -way edge connector strip (or see stylus lead which now goes direct to the HOLD capa-
text) citor is also connected through a decoupling capaci-
Materials for stylus (see text) tor to an a.c. detector circuit which, through an
5 -pin 180° DIN socket
integral switch, is used to trigger the ENVELOPE
SHAPER.

60 Practical Electronics January 1975

 Four components only go to make up the HF HF DETECTOR
OSCILLATOR which is shown in Fig. 3.4. The circuit of the DETECTOR is shown in Fig. 3.5.
VRI controls the frequency of operation by pre- IC2 is a high gain follower decoupled from the
scribing the proportion of positive feedback and stylus lead by means of C2. Cl provides additional
thereby varying the peak to peak value of the output decoupling for the stylus lead thereby ensuring that
signal. With the component values given the hum signals which may be included in the lead do
frequency range is from 2kHz at I8V peak -to -peak, not cause triggering of the envelope shapers. C4
to 250kHz at 80mV peak -to -peak. Output wave- and C5 provide frequency compensation for IC2
forms are also shown in Fig. 3.4. which is a 709 operational amplifier to give the
advantage of the higher gain bandwidth offered by
this device.
OSCILLATOR FREQUENCY The output of IC2 provides drive to TR I the col-
The optimum setting of the HF OSCILLATOR is lector of which is coupled through R6 to the bases
40kHz at 6V p -p as measured at point "AA." The of TR I and TR2 on both ENVELOPE SHAPERS. (Note
attenuating effect of Cl, RIO and VRI in the KBD that this latter coupling is via the DIN socket and
CONTROLLER will combine to reduce the signal to JK I on both ENVELOPE SHAPERS.) C6 blocks any d.c.
500mV p -p measured on the keyboard contacts. appearing at the output of IC2 while R5 sets a
It should be noted however that the setting of current limit.
VRI in the controller will affect the level of the h.f. Under quiescent conditions the output of IC2 is
signal-the lower the setting of VR1 the lower will nominally zero volts and TR I is off. An a.c. signal
be the level of the signal on the contacts. This is of sufficient level on the stylus lead will cause IC2 to
not really a problem since the detector sensitivity is follow and each positive excursion of IC2 output will
around 50mV and also, for most applications, it will switch TR 1 on causing the collector to go to about
be found that VRI will require to be at a relatively -8.5 volts. The ENVELOPE SHAPERS thus start to
high setting. attack and C7 receives a negative charge.

NJ. OSCILLATOR AND DETECTOR

To Stylus R7 DIN SKT

"I'41-/VV%-7(20k.0. -"IL ink (see text)

To Pin 2
I C4 C7 RODIN SKI.
3 I
1
VR1 CI i C2 0.19F 22k0
0.017 001 68pF
I'll CI RIO pP pF +9V
114914

95 C6
R1
200
kfl
0.01pF 8C1 84

C3
001
2kHz 180 P -P F

R3 1.2/411 I 4709F
C1 R1 I8
1000 10
Frequency
kfl
pP kfl r:isumd 250k Hz 800 P -P -9V
at

AAJ
Fig. 3.4. Circuit of the HF OSCILLATOR. Components Fig. 3.5. Circuit of the HF DETECTOR. Resistor R7
in the dotted box are on KBD CONTROLLER circuit is for isolation and was 2Oks2 in the prototype. The
and are mounted on main board. Typical waveforms DIN socket is for external keyboard attachment and
at different settings of the VR1 are also shown wiring options will be described next month. C1 is
mounted on the DIN socket

HF DETECTOR
COMPONENTS . . .
Resistors
HF OSCILLATOR R1 200k St R5 3.90
Resistors R2 10kS2 R6 22kt2
Rt 10k12 R3 1 8k S2 R7 200 (see text)
VR1 1001ffl subminiature horizontal skeleton R4 1 2M S2
preset Capacitors
C1 -C3 001µF (3 off) C6 0.01p.F
Capacitor C4 68pF C7 0.1t,F
C1 1000pF C5 10pF C8 470,uF 16V elect.

Integrated Circuit Semiconductors

IC1 Type 741 8 -pin d.i.l. D1 1N914
IC2 Type 709 8 -pin d.i.l.

61
Practical Electronics January 1975
 57
2mm socket for
insertion of Stylus
The cover is shown in Fig. 3.6. The wire from
lead the stylus socket on the side of the KBD cover would
then be routed to one end of the potentiometer
while the slider would go via R7, or inductor as
57
mentioned above, to pin I on the DIN socket.
RING MODULATOR
The Minisonic RING MODULATOR is an improved
version of the circuit which originally appeared in
the P.E. Sound Synthesiser (August 1973). The
essential features of the circuit have been retained
however and the circuit is shown in Fig. 3.7.
The RING MODULATOR produces a unique output
all dimensions In as waveform which comprises, at the same instant, the
sum and difference between any two applied input
frequencies. This function is carried out in a
purpose-built integrated circuit, the SG3402N. With
one of the input frequencies fixed, variation in the
other will ring the changes in the output frequencies
as shown in Table 3.1.
Fig. 3.6. Dimensions of the keyboard cover which was Referring to Fig. 3.7, RI and R2 form an input
made from 3mm card attenuator on the so-called carrier input (pin 7) such
that, when driven from a vco, the input signal level
at Cl will be about 40mV.
Similarly R3 and R4 attenuate the modulator or
The time constant of C7 is such that it will lose control input so that, when driven by a vco, the
only a small proportion of its charge during the input at C2 is about 200mV. This procedure results
negative half cycle of the h.f. signal. The result is in an output signal of about 1.5 volts at pin 4 and
that an effectively constant negative signal is pre- the same signal in antiphase at pin 11. The anti -
sented to the ENVELOPE SHAPERS during the period phase signals are amplified differentially by 1C2 to
that the stylus and/or key contacts are made. give a peak output signal of three volts which is
then attenuated by R9 and R10 to a level com-
ISOLATION RESISTOR patible with the remainder of the Minisonic circuits.
In addition to the components making up the SETTING UP THE RING MODULATOR
DETECTOR Fig. 3.5 also shows a resistor, R7, in series
with the stylus lead and HOLD circuit. The purpose Setting up the RING MODULATOR is very simple.
of this resistor is to provide a degree of isolation for With the circuit completed link the modulator input
C2 in the HOLD circuit so that its relatively large to the OV rail and connect the output to a suitable
capacity will not over -attenuate the signal on the power amplifier. Apply a signal of about 1kHz to
stylus. the carrier input (normally connected direct to vcol)
R7 (20kS2 in the prototype) also provides a delay and adjust VR1 until the output signal reduces to
in the d.c. charging rate of C2 with the result that the lowest possible level. This should, with a cor-
there is a 20ms portamento effect. This effect is rectly wired circuit, be 50dB or more below the
not really too noticeable unless consecutive KBD peak signal level. At this point the RING MODULATOR
voltages are programmed from opposite ends of the is correctly balanced with minimum carrier break-
KBD but it could perhaps be a source of irritation through.
for the constructor wishing to use the Minisonic for
serious musical purposes. NOISE GENERATOR
In these circumstances R7 could be replaced by The NOISE GENERATOR IS built round the highly
an inductance which would provide the degree of successful ZIJ noise diode manufactured by Semitron
a.c. isolation required whilst presenting only a Ltd., and is shown in Fig. 3.8. Output from the Z1J
nominal resistance to d.c. A suitable choke could be
made up from a small ferrite ring toroidally wound
with about 20 to 30 turns of 34 s.w.g. enamelled
copper wire.
Some experimenting will possibly be required to
get just the right value and it would be best to start
with the greater number of turns and reduce these
as necessary to get the best balance between a.c. Table 3.1: OUTPUTS FROM THE RING
isolation and d.c. resistance. MODULATOR

PORTAMENTO Frequency
As a modification to the prototype circuits some Carrier 700 600 500 400 300 200 100
constructors may wish to incorporate a variable Modulator 400 400 400 400 400 400 400
portamento control. In view df the lack of space on Sum 1100 1000 900 800 700 600 500
the front panel the best way to do this is to mount Difference 300 200 100 0 100 200 300
a miniature edgewise volume control-such as is
used on some transistor radios-inside the upper
edge of the printed circuit keyboard cover.
Practical Electronics January 1975
62
 RING MODULATOR

Input from VC01

(Pin.A on ES/VCAI P.C.B)
+9V
COMPONENTS . . .
SKI
EE R8

RI
8
R3
200 470. RING MODULATOR
kA A CI R5
+9V Resistors
R1 1.8kS2
7

ICJ 47 1(11
IC 2 6
R2 -R4 2000 (3 off)
12
R6 741 R5 -R8 47k0 (4 off)
SG 3 402N A/v.711 + 4
R9 1kS1
10
47kfl 9V R10 4700
14
Potentiometers
VR1 1000 subminiature horizontal skeleton
8
R4 SRI 10uF
preset
200 100 VR2 10k0 log carbon
1 k 11
kn

Capacitors
C3 C4 R7 RIO SK2 C1 -C4 10µF 6.3V tantalum (4 off)
00 10 47 470n C5 10pF 16V tantalum
kfl
T 14 13 12 11 10 9 8
Output
Integrated Circuits
-o-o-o-o-o-o-o- ICJ SG3402N
SG 3 402 N IC2 Type 741 8 -pin d.i.l.
M Top view

-o-o-o-o-o-o -o- Miscellaneous

2 3 4 5 6 7
1
SK1, SK2 2mm sockets (2 off)

Fig. 3.7. Complete circuit of the RING MODULATOR

is amplified by the high gain follower ICI and led, In the prototype the noise generator ceased to
through decoupling capacitor C5, to the volume work when the battery voltage had reduced to
control VR I. ± 7.8V. This situation may be corrected to a
The NOISE GENERATOR is the only circuit in the certain extent by shorting out R2 and R3 and/or
Minisonic which does not operate completely suc- by reducing the value of RI to, say, 82k12. No set-
cessfully down to a battery voltage of ± 7.5 volts. ting up is required for this circuit.

NOISE GENERATOR

COMPONENTS . . .
NOISE GENERATOR
Resistors
R1 91k0 R5 200k 0
R2, R3 220 (2 off) R6 56k0
R4 470k0 R7 1-2k0
Potentiometer
VR1 10k0 linear carbon
Capacitors
Cl 0.01p.F
C2 100p.F 25V elect.
C3 0.01/iF
C4 100p,F 25V elect.
C5 0.01µF

Integrated Circuit and Diode

IC1 Type 741 8 -pin d.i.l.
D1 Z1J noise diode (Semitron)
Miscellaneous
SK1 2mm Socket
Fig. 3.8. Circuit of the NOISE GENERATOR

Practical Electronics January 1975 67

 R2

Input from Fig. 3.9. Circuit of the CONTROL ENVELOPE IN-

(VGAI VR4 if)
5112
VERTER. This is fed with the output of ES/VCA1
via VR4 (see last month)
COMPONENTS ...
R1, R2 47k (2 off)
IC1 Type 741 8 -pin d.i.l.
SKI, SK2 2mm sockets (2 off)

POWER AMPLIFIER
MIXER STAGE OUTPUT STAGE

+9V
Ft7

Al Output to
Recorder or
Ext. P.A.

Fig. 3.10. Complete circuit diagram of one of the POWER AMPLIFIERS with integral two -input mixers.
Note that the mixer stages are mounted on the main circuit board

CONTROL ENVELOPE NOISE GENERATOR POWER AMP.1 POWER AMP 2

45COMPONENTS . . .
21I

POWER AMPLIFIERS
AND MIXERS
(2 off)

Resistors
R1 -R3 470 (3 off)
R4 1 5k0
R5 9100
R6 1k0
R7 4.7k0
R8 101(11

Potentiometer
VR1 100 log carbon

Capacitors
C1 4-7p.F 35V tantalum
C2 0.005µF ceramic
C3 3300pF
C4 220/iF 40V elect.
(or 470µF 16V)

Integrated Circuits
IC1 Type 741 8 -pin d.i.l.
IC2 MFC4000B

H.F. OSCILLATOR Miscellaneous

LS1 3in 15 speaker
SKI 2mm socket
Fig. 3.11. The Veroboard panel which carries the NOISE GENERATOR, JK1 3.5mm jack socket
HF OSCILLATOR AND DETECTOR, CONTROL ENVELOPE INVERTER,
AND POWER AMPLIFIERS

64 Practical Electronics January 1975

 NEXT
MONTH...
MARINE SPEEDOMETER
Solid-state electronics provide an easy -
to -make solution to the measurement of
boat speed-suited to both motor and
sail environments and giving reasonable
accuracy at sensible cost.

Fig. 3.12. The layout on the main Veroboard panel,

the majority of which was shown last month

CONTROL ENVELOPE INVERTER

Shown in Fig. 3.9, the CONTROL ENVELOPE INVER-
TER represents a modification to the prototype instru-
ment and has been included, principally, so that the
V( may be programmed automatically from
ENVELOPE SHAPER 1. The inverter itself is a simple
unity -gain inverting amplifier which requires no set-
ting up procedure.
AC/DC MILLIVOITMETER
A fully protected voltmeter which will
POWER AMPLIFIERS read a.c. voltages down to 5mV r.m.s.
The complete circuit of the power amplifiers, but will withstand overloads of up to
which includes a two -input inverting mixer, is shown
in Fig. 3.10. As with all the virtual earth circuits 250V. Operates at all audio frequencies.
in the Minisonic the mixer has the minimum number
of inputs and almost any number of additional
inputs may be applied by following the basic details
given in Part 1 of the series.
The slider of the volume control (VR1) at the
mixer output is wired directly to a jack socket from
which may be taken a signal suitable for driving an
PROBABILITY
external power amplifier, tape recorder, external
mixer, etc. ANOMALY DETECTOR
CIRCUIT BOARD LAYOUT Investigate your powers of extra -sensory
The CONTROL ENVELOPE INVERTER, HF OSCILLATOR
and DETECTOR, NOISE GENERATOR, and POWER AMPLI-
perception with this specially designed
FIER stages are carried on a separate circuit board unit. A meter registers your influence
which is illustrated in Fig. 3.11. on the random noise in a Zener diode-
The KEYBOARD CONTROLLER, RING MODULATOR and the greater your power the higher the
POWER AMPLIFIER/MIXER stages are all included on reading.
the main circuit board part of which was illustrated
last month. The remainder of the board is shown
in Fig. 3.12.
Next month: Final wiring -up and adjustments. Key-
PRACTICAL
board options, as well as circuit additions for more
ambitious constructors will be discussed.
Stop Press: The author has developed a printed circuit board FEBRUARY ISSUE ON SALE JANUARY 10, 1975
to carry all the Minisonic electronics. More details next
month.

Practical Electronics January 1975

 negative going transition at the col-
lector of TR2 is communicated via
the bootstrap connection of C2 to

S5111 the base of TR1. This results

TR1 being cut off and C3 now acts
as an effective collector potential
for TR2. Therefore C3 discharges
in

4`" A selection of readers'

suggested circuits. It
should be emphasised
through R3 until the emitter poten-
tial of TR I is again negative with
respect to the base. Thus TR1 con-
ducts and thereby completes the
cycle and .the whole sequence will
start again.
that these designs have If the time constants RI-C1 and
not been proven by us. R2-C2 are sufficiently large, the
They will at any rate frequency of oscillation is pre-
stimulate further thought. dominantly determined by C3/R3
Any idea published will and C3/R4. Current consumption
be awarded payment from a 9V battery is only 0.7mA
according to its merits. since the circuit only consumes cur-
Why not submit YOUR
IDEA? rent during one half period of the
cycle.

96
A SERIAL CONNECTION
MULTIVIBRATOR R2
ickn
I CO (pfl FREQUENCY 11-1z)
0.47 250
C22 500
TR' 0068 850
ASIMPLE square wave generator BC10E,

with equally fast rise and fall 10,F

times is always useful. The con- 6V

C3
ventional astable multivibrator has SEE TAME
the disadvantage that although one C4 OUTPUT

edge of the output waveform is fast, 0

the other edge is comparatively TR2 106E I6V

slow. This is due to the fact that BC108

the collector of the off transistor

has to recover to the potential of 1GuF 16,
R4
the supply in a time determined by 6 8k8
the capacitor associated with the
collector and the value of the col- Fig. 1
lector load. Improving the output
waveform by the use of extra
diodes or perhaps an extra tran- so this capacitor charges exponen- Unlike its more conventional
sistor are solutions but a novel tially allowing the emitter of TR2 counterpart the serial connection is
approach is a serial connection. to approach ground. always self starting. The output
Consider the circuit shown and When the charging current has amplitude with the circuit shown is
let TR1 be fully conducting and decreased sufficiently so that the 5.5V peak -to -peak.
TR2 cut off with C3 fully dis- base potential of TR2 is again more
charged. It will be evident that C3 positive than its emitter, then this M. Harding,
has a charging path via R4 and transistor promptly conducts. This Cheadle, Cheshire.

SOUND/LIGHT MODULATOR MAC 11-6. This is possible as the To provide frequency sensitivity
triac drive pulses need not be and/or other channels, capacity can
shaped. be inserted in the triac gate circuit.
AVERY simple sound/light Using 100V I p.F capacitors, bass
modulator is shown in Fig. 1 response can be selected by inserting
which may be of use to experi- the capacitor in parallel with the
menters. Input signals can be taken secondary of the transformer. For
from the output (loudspeaker) of an the treble the capacitor is in series
audio amplifier since in most pop or with the gate and for the mid ranges
disco environments the small two capacitors are used, one in each
amount of distortion introduced of the foregoing positions.
using this method will hardly be In this way three circuits can be
noticed. built up to control three separate
Sensitivity is controlled by VR1 lamps if desired.
whilst the transformer provides P. Vleck
isolation and the drive for triac Fig. 1 Cheltenham.

66 Practical Electronics January 1975

 electronics
lookI really
mastered
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...visual
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no previous knowledge
no unnecessary theory
no "maths"

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step by step, we take you through all the fundamentals of
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OSCILLOSCOPE AND UNDERSTAND
CIRCUIT DIAGRAMS
You learn how to build
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RAPY electronics. various fields of electronics.

3/ CARRY OUT valve experiments, transistor experiments This new style course will enable anyone to
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OVER amplifiers, oscillators, signal tracer, pho-
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40 EXPERIMENTS radio receiver, electronic switch, simple a minimum of theory-no previous knowledge
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ON BASIC ELECTRONIC transmitter, a.c. experiments, d.c. experi-
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THEY WORK, including : receivers, etc.

,71111111
i POST NOW To BRITISH NATIONAL RADIO & ELECTRONICS SCHOOL, DEPT. EL124, P.O. BOX 156,
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Practical Electronics January 1975 67
 COLOUR TELEVISION WITH
WILMSLOW PARTICULAR REFERENCE

AUDIO TO THE PAL SYSTEM

by G. N. Patchett Price E510

THE Firm for speakers! ELEMENTS OF TRANSISTOR PULSE

Price L3.70.
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UNDERSTANDING IC OPERATIONAL
AMPLIFIERS by R. Melen. Price 12.20.
Goodmans 10P 8 or 15 ohm E5,30
SPEAKERS Goodmans 12P 8 or 15 ohm
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BEGINNER'S GUIDE TO ELECTRONICS
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Baker Group 35 3. 8 or 15 ohm (11-50 Goodmans Audiornak 12AX 100W (39-55 ELECTRONIC .EQUIPMENT
BILITY by J. C. Cluley. Price E2.65.
Baker Group 50/12 8 or 15 ohm £12.50 Goodmans Audiomax 15AX (42.00
Baker Deluxe 12m d/cone
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(10.75 Goodmans 15P 8 or 15 ohm
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Baker Regent (7.75 Goodmans Midas 750 (1600 Price LI55.
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Celestion MH1000. B or 15 ohm (10.95 Goodmans Axiom 401 12in [17.25 SYSTEMS by N. M. Morris. Price L240.
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Celestion G12H 8 or 15 Ohm (15-00 Kef T27 (5.25 H. G. McEntee. Price a.m.
Celestion G15C 8 or 15 ohm (24.00 Kef T15 [6-00
Celestion G18C 8 or 15 ohm (33.00 Kef 0110 (7-25 DIGITAL LOGIC BASIC THEORY AND
Coral 63in &tone roll surr 8 ohm (2-50 Kef 8200 (8-25 PRACTICE by I. H. Smith. Pr ice 11.65.
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EM 13in x 8in 3. 8 or 15 ohm (225 Kel DNB (2.00 UNDERSTANDING AND USING THE
EM 13in x 8in 150 cl/c 3. 8 or 15 ohm (2.50 Kel DN12 (415 VOM AND EVM by J. Cunningham.
EM 13in x Bin 450 Vtw. 3. 8 or 15 ohm (3.75 Kel DN13 [3.30 Price MISS.
EM 13in x 8in type 350 8 or 15 ohm (8.25 STC4001G super tweeter (8-15
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GE TRANSISTOR MANUAL Price [130.
EM Sun 93850 4 or 8 ohm (3.00 2iin 64 ohm 70mm 80 ohm. 70mrn 8 ohm (0.65 * TOTAL PRICE INCLUDES POSTAGE *
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EM 2iin tweeter 97492AT [0.55 Bin x 5in 3 or 8 ohm £1.50
Eagle DT33 30W tweeter (5.45 10in x bin 3 8 or 15 ohm [2.30
Eagle HT15 horn tweeter
Eagle CT5 cone tweeter
(3-110
£1.75 THE MODERN BOOK CO.
Eagle CTIO tweeter 8 or 16 ohm [2.55 BRITAIN'S LARGEST STOCKIST .

Eagle MHT10 horn tweeter

Eagle crossover CN23. CN28, CN216
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£1045
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Goodmans DIN 20 each (9.75 LONDON W2 INP
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hn Practical Electronics January 1975

 socket into which the service Another was a rechargeable unit
engineer plugs his monitor. The that could be recharged by induc-
monitor has 13 led's and if any tion through an external unit. But
one of these fails to light up there both these solutions are losing
is an indication of a specific fault. favour, mainly expense in the
It costs very little extra on each nuclear field and susceptibility to
set to provide the facility and the outside interference with recharge-
saving in engineer's time can be able units, apart from the occa-
enormous. And, of course, with sional inconvenience to the user.
soaring labour costs, time saved It seems now that long -life bat-
is very important, not to mention teries will do the job quite well.
INDUSTRY customer satisfaction. The plug-in
diagnostic aid costs the dealer
Reasons are that in the early days
pacemakers were more powerful
under £10. Quite a bargain. And than they needed to be, the new
the customer benefits, too. Other active devices using technologies
set makers are expected to follow such as CMOS take far less cur-
NOTEBOOK the trend. rent, and battery technology itself
has improved.
With current drain reduced to
less than 20 micro -amps a three-
year life can be obtained from
EXPORTS mercury -oxide -zinc units and pos-
If you've ever thought that export sible developments in sodium -
promotion is not given enough bromine and lithium cells could
priority in Britain, reflect for a give a battery life of seven years
moment on the current trading or more. This figure ties in well
quarter which ends on December with the life -expectancy of pace-
31, 1974. The British Overseas maker users who statistically have
Trade Board is giving support to an average age at implant of 67
EASIER SERVICING 1,360 British companies at 76 over- years and can expect another 5-7
seas trade fairs in 27 countries. years of life.
Colour television is easily the
most complicated box of tricks in In addition there are 54 outward
the home. Healthy competition has trade missions representing 730
kept prices low, despite inflation. companies and involving 45 coun- HUMBLE HARDWARE
And that same competition, in tries. These group activities are in Racks, panels, instrument cases
effect the struggle for market addition to hundreds of "private" hardly ever hit the headlines. Yet
share, is still spurring manufac- promotions by individual com- they are still big business in elec-
turers to give the buying public panies. tronics clocking -up European sales
more and more value for money. One of next year's big trade of over £30 million a year and
It follows that the more complex drives is to be centred on Western double that ifyou add in PCB
a machine is the more it costs to Canada and seminars are already edge connectors and other inter-
service. And TV sets, by their very being held in Britain which will connection devices. So don't
nature, have a fine in-built monitor, brief exporters on trade opportuni- despise the metalwork in elec-
the screen itself, which instantly ties in advance of parties of ex- tronics. It might not make so much
shows up defects or deterioration porters visiting the two big growth profit as glamour products but the
in performance. The broadcast areas of Alberta and British commercial risk is much lower.
authorities are even kind enough Columbia. In the direct field of Provided, of course, that you can
to transmit test patterns designed electronics, one of our biggest get your materials. One prominent
to highlight imperfections. 1974 efforts was at Munich's Elec- manufacturer, lamenting recently
manufacturer has night-
Every tronica Exhibition which 57 at on production hold-ups, commented
mares over servicing. Apart from British companies took part in a that "screws have seemingly
losing goodwill, every time a set joint venture. ceased to exist, and costs have
goes wrong during guarantee gone up alarmingly". And steel,
another chunk of profit goes down plastics and paint have also been
the drain. So in their own interests, hard to get.
manufacturers do genuinely try to
make sets that are reliable and PACEMAKER BOOM
there has been a strong move over It was only a few years ago that TAKE OFF
the past few years to build sets we were all marvelling at the way Great sighs of relief that the
in modules to allow servicing by microelectronics had made possible European Multi Role Combat Air-
module replacement. the heart pacemaker which has craft has received the go-ahead
Now Grundig in Germany has done so much to extend human for its final development phase.
gone one step further by building life. With improved techniques in This is the project that is exercis-
in a rapid diagnosis system in implant surgery and technical ing the best brains in electronics.
every set. Grundig had switched advances in pacemakers this single It's costing the earth, of course,
to a nearly fully modular system branch of medical electronics has but how else do you keep ahead
some three years ago in which 75 now blossomed into an industry in in technology?
per cent of the circuitry is split its own right with world sales this At a more mundane level it's
among a dozen plug-in modules, year expected to top £25 million good to see Plessey has started
each with a defined function. If and reach over £200 million by delivering ILS systems for Chinese
any one module failed it was fairly 1980. airfields in a contract worth
obvious to the service engineer The technical problem which has £850,000. And British aerospace
and he just plugged in a replace- been engaging pacemaker re- companies as a whole are doing
ment. Now the diagnostic adaptor searchers is how long they can be well with exports worth more than
enables an instant check of the kept working without recourse to £2 million every working day with
non -modular circuits. further surgery to replace the our best customer still being the
Key check -points of the circuits battery. One approach was to use United States followed by France
are all brought to a single 13 -way nuclear power to give infinite life. and Germany.
Practical Electronics January 1975 69
 towards the use of a product com- coils, tubes and printed circuit
patible with existing tape and equip- boards separately.

MARKET ment rather than the current trend

of using metallic dioxide tape. It is
claimed that the new tape combines
the high frequency abilities of
For full details readers should
write to Crofton Electronics at 124
Colne Road, Twickenham, TW2
6()S.
chromium dioxide with the bias We understand that Re An

PLACE
Items mentioned in this feature are usually
characteristics and low frequency
response of the low -noise
oxide tape.
ferric
Both the above tapes are available
Products, Ltd are able to supply all
the control knobs (19 with skirts
and one without) for the P.E. Mini -
sonic synthesiser. These knobs have
available from electronic equipment and corn- from all good audio shops and large a translucent numbered skirt and
oonent retailers advertising in this magazine. stores. are available with coloured caps.
However, where a full address is given,
enquiries and orders should then be made direct It has been suggested that by using
to the firm concerned. All quoted prices are a colour code system for the knobs
those at the time of going to press. LITERATURE the front panel layout of the Mini -
A comprehensive 724 -page data sonic can be identified in colour
book covering Motorola's range of groups (i.e. envelope shapers, volt-
MOUNTING PILLARS linear i.c.s is available from Semi - age controlled oscillators and ampli-
A useful new product for the comps Ltd. The book contains not fiers, etc.), which can make the
only full data but, in many cases, instrument easier to use.
constructor has just been released valuable application information on A price list for the knobs, type
by West Hyde Developments Ltd. over 300 devices. R62, is obtainable from Re An
Called Ilex pillars, they are designed The range includes op. amps, Products Ltd, Burnham Road, Dart-
to insulate circuit boards from cases drivers and line receivers, d/a and ford, Kent, DA1 5BN.
or chassis and at the same time a/d converters, comparators, voltage What is believed to be a unique
support them either vertically or regulators, timing and power control service for the private constructor,
horizontally one on top of another. units, consumer TV, audio and has been announced by SCS
Made from moulded nylon, they radio circuits, r.f. amplifiers and Components.
have a rigid girder -shaped support- automotive circuits. Now, branded guaranteed com-
ing section with a spring loop For easy reference the data sheets ponents are being offered at very
fastener at the top and tension feet are arranged in alpha numeric competitive "one-off" prices, in fact
together with a push -in clip at the sequence without regard to product the same as applying to industrial
base. category. users. Included in this offer is a
Suitable holes are drilled in the The book costs £1.26 and is very large range of integrated
chassis and boards and the pillars obtainable from Semicomps Ltd., circuits and transistors.
are simply pressed into place and Northfield Industrial Estate, Beres - A complete price list (free) is
any subsequent boards mounted on ford Avenue, Wembley, Middlesex, obtainable from SCS Components,
the top of the pillars, see photo- HAO 1SD. Northfield Industrial Estate, Beres -
graph. The sizes of the pillars vary ford Avenue, Wembley, Middlesex.
from in to I4in and cost approxi- To help beat rising costs Amtron
mately 3p each for a minimum NEWS BRIEFS U.K. Ltd. are now able to supply
order of 10 (for +in size). Readers who are building the direct to the customer many of their
Full particulars and sizes together "P.E. CCTV Camera" may be inter- more expensive electronic kits.
with price list can be obtained from ested to know that Crofton Elec- A full 'list of the construction kits
West Hyde Developments Ltd., tronics are now able to offer a available is obtainable from Amtron
Ryefield Crescent, Northwood Hills, complete kit of parts for this pro- U.K. Ltd., 4 Castle Street, Hastings,
Middlesex, HA6 INN. ject. They can also supply lenses, Sussex TN34 3DY.
ON TAPE
Two new cassette tapes have been New p.c.b. mount-
announced recently by EMI Ltd ing pillars from
and 3M United Kingdom Ltd. West Hyde
The new X1000 ferric oxide cas- Developments
sette from EMI is claimed to give
as good reproduction as chrome
dioxide cassettes. A C60 cassette is
expected to retail at 99p (excluding
VAT).
The main technical improvements
claimed for the X1000 are: an
increase of 3-4dB in the 8-15kHz
frequency range, compared to low
noise tapes. A wider dynamic range
due to the tape's increased magnetic
remanence, resulting in less tape
hiss. Improved high frequency
response ensures a low level of
intermodulation distortion.
When used with good quality
audio equipment the tape is claimed
to give excellent performance down
to 25Hz and up to 15kHz. X1000
Undoubtedly the new Scotch Cassette At'
Classic tapes from 3M's, with a C90
cassette at £2.16, is aimed at the
"serious" end of the market.
This new double coated or dual
layer tape indicates the trend 3M's Classic cassette tape The X1000 cassette tape from EMI

70 Practical Electronics Januar 1975

 HEADPHONES, CALCULATORS, DIGITAL CLOCKS, QUADRA-
PHONIC RECORDS, TECHNICAL BOOKS, TESTGEAR, SQ.
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We will be supplying kits for the PE Joanna Electric Piano, the PW Electronic Organ, and
PW Ascot Cassette Recorder.
All the above, and many other items are in our new 1975 catalogue available FREE NOW!
A large S.A.E. (7p in stamps) would be appreciated.
Trade and export customers are invited to apply in writing for distribution terms of
business.

SUPERB QUADRAPHONIC SYSTEM

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Complete kit with 4 speakers, u/c decoder, FM tuner and turn- £195 £.15 60 VAT
table. Value approx. £209 H- £16.72 VAT.
Fully built Rondo, complete as above. Value £266 £21 VAT. £245 £19.60 VAT
Delivery on complete systems may be 6/8 weeks from date of
order.
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very professional finish. Very comprehensive kits.
We supply all Rondo parts and modules.
Quadraphonic headphones-a new experience! £1850 £1.48 VAT
Stereo Headphones-padded with volume controls. £4.80 38p VAT

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We are appointed distributors for Uher quality tape recorders and Videosonic
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Have you had our book list?
NAME

El V El Studio Electronics ADDRESS

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P.O. BOX 18 HAR LOW
CM 18 BSH ESSEX
Telephone Harlow s t d 0 2 7 9) 2 54 5 7 PE 1 75

Practical Electronics January 1975 7I

 INTRODUCING

SEAS by Macel
The Elite of High Quality
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INTRODUCTORY OFFER INCLUDES VAT AT 8% AND POSTAGE (UK ONLY)
(ALL KITS INCLUDE FULL WIRING DIAGRAM AND CABINET DRAWINGS)

comine hobby with pleasure

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The following include High Compliance Bass Units and Cone Middle/Treble Units.
KIT 91H: 2 way and crossover (1 x 6f" plus 1 x 31") (8-18 litre box) 10 watts 60-20,000 c/s. £7.35 each.
KIT 94H: 3 way and crossover (1 x 11 x 6f" plus 1 x 31" plus 1 x 2") (25-40 litre box) 25 watts 45-20,000 c/s.
£13 25.

The following include Neoprene Edge Bass Units and Dome

Middle/Treble Units. Outer connecting lead and all internal wiring
with mechanical push -on connectors.
r To MACEL ELECTRONICS LTD
KIT 10-2: 2 way and crossover (1 x 6f" plus 1" dome) (8-12 litre IP.O. Box 64, 14 High Street, Ipswich IP1 3LR
box) 20 watts 45-20,000 c/s. £15.35. ITel. 0473 216465
KIT 18: 2 way and crossover (1 x 8" plus 1f" dome) (15-20 litre enclose cheque/postal order
box) 30 watts 35-20,000 c/s. £16.30. I1 for
KIT 30: 2 way and crossover (1 x 10" plus 1f" dome) (25-35 litre
box) 35 watt 30-20,000 c/s. 06.95: INAME
KIT 35: 3 speakers and crossover (2 x 8" plus 11" dome) (30-40 IADDRESS
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I 1
72 Practical Electronics January 1975
 BOON NEWS BRIEFS
G. D. SHAW LECTURES AT AUDIO FAIR
tremendous interest in synthesisers was reflected
ROBOTICS THE
by the massive attendance at the two lectures at
By John F. Young this year's Audio Fair by G. D. Shaw, the author of
Published by Butterworths P.E. Minisonic articles currently appearing in Practical
300 pages, 84in x5fin. Price £6.00 Electronics.
Entitled "Sound Synthesis for the Amateur", the
IS nothing mythical about this book. II is lectures described synthesisers ranging from the simplest,
THERE
concerned with hard facts of engineering. Robots in the form of the Minisonic, to the synthesiser of the
have a very real existence, and in various forms perform future in the form of a digitally organised instrument
many useful tasks in industry and elsewhere. Tasks having full polyphony (the ability to play more than one
which range from the mundane and repetitive to- those note simultaneously), and a memory facility.
of a highly speciilised and skilled nature. The part of the lecture dealing with the Minisonic
All this is clearly brought out in Robotics. The author, was illustrated with some impressive tape recordings
who has had a long experience in this field, describes made, using the Minisonic, by Malcolm Pointon. Most
notable developments in robot design which have been people were amazed at the range of effects that could
or are currently being undertaken in various advanced be produced by such a simple instrument.
countries. Some of the devices mentioned will be familiar, In the realm of digital synthesisers. Mr Shaw hopes
like the Lunakhod, the Robotug, and the mobile robot to be the first to produce a design suitable for the
used by the army to explode bombs left in cars. But amateur, a formidable task when one appreciates the
there are many other significant developments in robotics complexity of such a system. The instrument is to be
which this book now brings to the attention of a wider designed in such a way as to allow expansion from a
audience. basic unit simply by plugging in printed circuit boards
Underlying all this activity are unmistakable signs of as and when they are needed (or can be afforded).
the eventual appearance of the General Purpose Robot This was not the only area where P.E. scored a
for domestic use. The idea of an automated housewife "sound" success. On our stand the "P.E. Joanna" piano.
is not just wishful thinking; it is the target of many exhibited for the first time, created enormous interest
designers in a number of countries. Indeed, according amongst the public. This unique instrument, ideal for
to the author, the Japanese are already well advanced the modern home, features piano, harpsichord and honky
with plans for a G/P Robot suitable for mass production tonk facilities with true touch sensitive operation.
with the inevitable economic advantages this will bring. The P.E. Joanna is a future project and full details
This book does not cover the "brain" of the robot, will be published in the next few 'months.
but concentrates upon the engineering of the "body".
Hydraulic, pneumatic, and electrical techniques for
actuation of the "limbs" are discussed. Electronics comes LINK(S) UP
into its own with the imitation of the human senses, almost unbelievable 5 watts of transmitted power
and all the commonplace sensoring devices are con- ANwas used, in conjunction with a satellite, 'to beam
sidered. Character and voice recognition pose greater a transmission over a distance of more than 50,000
problems; some indication of recent work by the author miles recently in America.
and his associates at Aston University in devising
circuitry to solve some of the difficult problems in this In an experiment involving a simple antenna made
frontier area of electronics is given. from a gblfer's umbrella, an engineer from the General
Extensive lists of references accompany each chapter. Electric Company of USA ..sed a low power "walkie-
Valuable as sources for the specialist researcher, these talkie" radio to prove that even with such rudimentary
items provide additional evidence of the determined equipment the only important requirement for long-
efforts that have already been made in this field of range communication is the presence of a satellite over-
Robotics, and indicate how the robot has already become head.
usefully employed in so many and varied everyday To be fair, the antenna was specially made up from
activities. the golfer's umbrella but nonetheless a morse message
was beamed from the NASA headquarters to a geo-
stationary satellite ATS-3 and then -to GE (USA)' s
ELECTRONICS - AN ELEMENTARY INTRODUC- Radio -Optical Observatory near Schenectady, New
TION FOR BEGINNERS (SI UNITS) York.
The demonstration shows all too clearly just how
By L. W. Owers easy it would be for almost world-wide coverage to be
Published by Publication Mailing Services provided for some form of search -and -rescue system
120 pages. Price L145 based on a simple man -carried emergency transmitter.
N LINE with the current tendency, this book is perfect It is also envisaged that the system could carry phone
I bound between linen covers to keep costs to a signals, not just morse.
reasonable level. It is nonetheless a valuable introduction
to electronics for any beginner, particularly those meet-
ing this type of subject for the first time. PRICE CUT
Diagrams are used extensively with the addition of N this period of constantly rising prices it is hearten -
formulae where necessary and these latter are spelt out I ing to know that at least some items are becoming
in SI units to conform to international practice. cheaper. Motorola have recently announced their second
The reader is led by the hand through complexities price reduction in the CMOS device area.
of fundamental particles, atoms, energy in its various This second reduction, worth an average of 25 per
forms, static and current electricity and the basic raw cent, applies to standard MC14000 and the in-house
materials of electronics from theory to simple example. MC14500 devices. When applied to MSI the new pric-
Finally. the theory is exemplified by discussions of ing will give an individual gate function cost at around
the valve and semiconductor and their use in radio and just a few pence and when this is coupled to the saving
television and other areas. in power supply requirements and package count the
R.D.R. total effect is a distinct improvement when using CMOS.
Practical Electronics January 1975 73
 Growing Upwards !
Sir-With reference to Mr. Crilly's
letter (Readout, September), I feel
that I in turn must draw attention
to two points.
Firstly, the magnetic properties of
A SELECTION FROM OUR POSIBAG a material are determined by the
spin configurations of the constituent
atoms or ions. The vast majority of
elements and compounds are said
to be paramagnetic-this means that
unbalanced spins among the elec-
trons leave a nett magnetic moment
on the atom. In the presence of a
magnetic field, at low temperatures
be destroyed by excessive current so that thermal vibrations do not
Gas Detectors at switch -on. For example, if a low upset things, a degree of alignment
Sir-As the comment appearing on voltage 6V to 24V circuit is used can occur.
page 794, September 1974 issue, then the minimum value of load In the case of iron and certain
may raise doubts as to the life of resistor is 2 ka A variable resis- other materials, ferromagnetism is
the TGS sensors, we trust the fol- tor alone should not be used in this observed. This means that over
lowing brief outline of the operating position as it is possible for the unit small regions of the crystal the mag-
principles of the sensor will indicate to be switched on with the variable netic moments (which are due to the
why we claim that their life is com- resistor set to the low end of its same mechanism as above) are
parable to that of other semicon- range. aligned by an internal crystal field.
ductor devices, rather than the D. Lahiff, These regions are called "domains",
catalytic type of gas detector. Manager, Figaro Engineering, and may themselves be aligned by
Molecules of flammable or de- Shannon, Ireland. an external field. Thus, ferromag-
oxidizing gases are absorbed on the netism is a bulk property of iron,
surface of the Taguchi sensors, and it is inaccurate to speak of iron -
resulting in electron transfer be- containing molecules as being more
tween absorbate and the solid sensor "magnetic" than magnesium contain-
surface. In the case of hydrocarbon .
ing ones without considering the
gases the reaction is related to the nett spins for the molecules
ionization potential of the gas
Gas Sense (or) concerned.
absorbed on the surface of the Sir-In the circuit of the "Boat/ Secondly, Mr. Crilly states that
pellet. The lower the ionization Caravan Gas Detector" (October strong magnetic forces radiate from
potential, the more readily is the 1974) the fact that the 1.e.d. is alight the centre of the earth. This is not
gas detected. Hence isobutane proves that the heater side of the strictly true; the earth's field is not
(ionization potential 10.79eV) is gas detector is connected and con- a monopole but approximates to a
detected more easily than methane ducting. A dangerous situation could dipole. As a result of this there are
(ionization potential 13.04eV). arise if the alarm circuitry, or more regions of the earth's surface at the
The change in conductivity of the likely the wire connecting it to the geomagnetic equator, where the field
sensor is not caused by heat result- detector, were to become open - is parallel to the surface-in fact it
ing from the combustion of a gas circuited. This problem could arise is vertical only at 'the geomagnetic
at its surface. The lack of combus- from corrosion of the B7G socket poles.
tion and relatively low operating or the gas detector pins (and boat The suggested mechanism of
temperature, 250°C, eliminates de- bilges are known to be very damp tropisms would, therefore, not work
terioration of the inert 82 per cent places). in general, producing horizontal
'Palladium + 18 per cent Iridium The simple modification shown in roots at the geomagnetic equator,
filaments encapsulated in the bead. the enclosed diagrams will enable and roots inclined to the vertical in
The Taguchi gas detectors have the detector to be fully tested each most regions. I should also point
been in continuous use in Japan for time it is turned on. The resistor out 'that plants transplanted from the
six years, and the only noticeable R16 corresponds to a concentration Northern hemisphere to the South-
change in performance has been an of approximately 0.2 per cent of ern would develop into roots grow-
increase in sensitivity with time, up Butane or Propane in air, well below ing upwards at an angle to maintain
to a maximum of 30 per cent when the inflammability range of 1.8 to their accustomed orientation with
a levelling -off occurs. 9 per cent. respect to the field.
Damage can occur to the sensor R. A. Wood, C. R. Francis,
if it is exposed for long periods to Wolverhampton. Sheffield.
high concentrations of gases con-
taining sulphur or lead, and such
gases will in any case inhibit the
performance of most gas detectors. TO R7/R8 TO R7/R8
PUSH TO TEST

There are of course, many appli-

cations where 'the catalytic type
sensor is superior to the Taguchi R16

especially in the areas of selectivity 3.90

and long term repeatability, but
where a pre-set low level long -life
sensor is required, the Taguchi have GAS GAS
found good acceptance. More than DETECTOR DETECTOR
two million have been put in service
to date.
From the design point of view,
it is essential that a current limiting
resistor be included in series with
the sensor, or else the sensor may TO TR4 /C5 r U R13 TO TR4/C5 TO R13

74 Practical Electronics January 1975

 U
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Practical Electronics January 1975 75

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mic and deck inputs. Ample headphone power is
available for P.F.L. May be used for mono and is
mains operated. Fitted with sturdy screening case. SAXON%
Controls: Mic vol, bass, treble. Left/Right fade, deck
volume, bass, treble, h/phone select, vol, Mains. Size
171 in 3in 4in deep. - -
DISCO MODULE E9.50 Carr.
20p
Thousands sold of this extremely popular mono version. A mic input may
u
be fitted using the VA30 (see below). Low consumption from a 9V battery. 1101.110, seaw
Features the same high standards of reproduction as the Stereo version.
Controls: H/phone select, vol, Left deck vol, Right deck vol, bass, treble,
master vol. Size 12f in 3in 2in deep. illsommoikale
3 -CHANNEL SOUND-LITE E22.50ThisCarr.
30p
unit features 3kVV
Only SAXON c an supply such incredible value for money.
Power handling, full -wave control, bass, middle, treble AND master controls. Twin
loudspeaker jacks for " through " connections. It may be used free standing or will
panel mount next to either of the above. Also features unique CUT -BACK circuitry
for extra wide range response. Size I 2in 3in i 2fin deep. Professional standards
A
at a price you can afford!
SINGLE CHANNEL Recently reduced in price
,d,l,nedp.t,o
Add 8% VAT to all orders saxou Somali Ilte
VERSION E750
Carr free operation
MULTI -PURPOSE MIXERS
M4HL M6HL
L19-50 csypr. L29.50 50p
c'''
Featuring multiples of our VA30 module, the M4HL
and M6HL fulfil the requirements of all clubs, groups, 411-411---41
etc. where a high quality mixer is required. Each
channel has one high and one low impedance input,
plus volume, treble and bass controls. Input
impedances may, if required, be easily changed,
The M4HL has four channels, and one output, and
the M6HL six channels (12 inputs) and a master
control and two outputs. Either unit may be used
11-11-4
free-standing or panel mounted. These mixers will
feed all types of amplifier. Recommended for their
versatility and high performance, and excellent
value for money.
°
VA30 NODULE
M
/3.511 C arr .
freeANNEL
Co 0 0 b. t)
This is the basic channel module in the above mixers
and may also be used for extra inputs on either the
mono or stereo mixers. Fitted with volume, bass
and treble controls, requires just a jack and supply SAXON
(9-100V)

SAXON 100W of speech and Four individually SAXON 100

music -Two controlled FET in-
COMPLETE
CSE separately controlled
inputs. Wide range b;a, V4 4 put stages plus
wide range bass AMPLIFIER
100
bass and treble
controls. Sturdy and
attractive vynide
case. Twin outputs.
MAT,/ 9
and treble con-
troll. 120W of
speech and music
output from
03.00
Carr. free
COMPLETE
Ideal for groups, twin loudspeaker
AMPLIFIER discos. etc. Fully sockets. Sturdy case, and an attractive facia make this SAXON 50
tested and excellent value for money. Hundreds in use by groups,
guaranteed. CSE 50 discos, clubs, etc. L37.50
E34.90 SOW version identical SOW version identical in appearance. Carr. free
Carr. free In appearance. E29.50 Carr. free
CALLERS AND MAIL ORDER: SEND !Op FOR OUR NEW 26 -PAGE

SAXON ENTERTAINMENTS LIMITED MANUAL-full circuits and details.

TERMS OF BUSINESS: C.W.O., C.O.D. or
327-333 WHITEHORSE ROAD CROYDON CR0 2HS ACCESS (just send in card number. Send
60p. for C.O.D.
(Please quote magazine when ordering) Please include S.A.E. with all enquiries.
SHOP HOURS: 9 a.m. 5 p.m. -LUNCH 12.30-1.30 p.m. MAIL ORDER DESK: 10 a.m.-3 p.m. VAT at 8% must be added to all
24 -HOUR ANSWER SERVICE TEL. 01-684 6385. TECHNICAL ENQUIRIES 01-684 0098 orders including carriage charges.

76 Practical Electronics January 1975

 bacon I could prove by Boolean
Parapsychic A Boolean Breakfast Algebra that it did not exist. One
Sir -I was recently having breakfast could not be charged, even in these
phenomena in an hotel and reading a book on times of rampant inflation, for some-
Sir -Sometimes I read your articles Boolean Algebra. I had reached a thing that did not exist whether one
about "ESP" in PRACTICAL ELEC- point where the author stated that ate it or not. The cost of breakfast
TRONICS with great interest. I'm A + (A.13) = A, when I realised should therefore be deleted.
working in parapsychic phenomena that the waitress was looking over The Manager appeared to have
as a "hobby" and I have some my shoulder. She asked whether I an entirely mistaken grasp of
results, which may interest you and would like egg, or egg and bacon. Boolean Algebra, and the adviser
your readers. My natural gluttony lead me to he called in had not even heard of
During the spring and summer I order egg and bacon. I continued it. Possibly Boolean Algebra does
discovered that a magnetic field reading and learnt that the expres- not form part of a constable's
stimulates germination and even sion above was read as "A or A and training.
growth of seeds and plants. I made B equals A", and that if either A Perhaps some of your more
experiments with lobelia, bindweed, or B is present it is given a value erudite readers can point out where
pea, lentil and various other plants. of I and if absent its value, reason- the fallacy lies.
In all cases germination increases ably enough, is 0. The author R. Parfitt,
about 20-30 per cent, germination proved the statement by a truth Croydon.
time was shortened by approxi- table.
mately 30 per cent and plants were At this moment ,the waitress
50 per cent higher than in control placed in front of me a plate on
tests. In addition, it is interesting which there was an egg but no
that the same effect was caused by bacon. Of course, I pointed out with
hand movement, so called "mag- maximum natural charm that I had
netisation", known 200 years ago ordered egg and bacon. I was sur-
and used by Mesmer for healing prised. even dismayed, when she
with "animal magnetism". said that what she had served was Make an offer
It is my opinion that these effects the same as egg and bacon, the Sir -Before my husband's death in
are caused by water polarisation book had just proved it by a truth May 1974 he had started to buy
in both cases. The same effect table -egg, or egg and bacon equals various parts for the "Electronic
is obtainable by using "magnetised" egg. Piano", described in your Magazine
water, activated by passing through Later, when the management pre- some time ago. He already bought
a strong magnetic field. sented me with the bill for bed and two manual contact assemblies, two
These two phenomena will be breakfast, I pointed out that the C -C keyboards, digital master oscil-
discussed and published in two para- bill for bed, or bed and breakfast, lator and other parts. Is it possible
psychological magazines. should be the same. In the tariff, for you to help me to dispose of
V. Patrovsky, breakfast was a separate item, and these items?
Czechoslovakia. although 1 had just eaten it, like the Mrs. E. Szwimer.

MONEY RACK IF NOT SATISFIED.

LARGE STOCKS. LON PRICES.
ROAD,58T-R3?!II 3 ALL BRAND NEW TOP GRADE FULL
SPEC DEVICES.CALLBRS WELCOME.

FAST SERVICE. SEND C.W.O. ADD VAT TO ALL PRICES IN U.K. P&P 15P, EUROPE 25P.OVERSEAS 65P. CATALOGUE/LIST FREE SEND S.A.E.

Digital Displays 702 OPA

703 RF/IF
U©9
69p
8 SemjcondugRars
MFC4000 IW AF 35p
SPECIAL OFFERS
vero
VERO PINSx36 25p.
,AltLOW Pap
MINITRON 3015F 28p 14FC4060 54p COPPER CLAD VEROBOARD 0.1"
0-9DP 11.15 ea 709 7099 21p 14FC6030 52p 741 29p MFC4000 35p
709 DIL 14 29p MFC6040 90p 555 67p 25414 11.09 21x5" 27p.21x31" 24p.32x33"27p.
LED 0.3. digit 710 DIL 14 .36p 14FC8010 11.10
3ix5" 29p.31x17" 11.50
0-9DP 11.49 ea 720 Radio 11.39 MFC8040 11 BC107.11C108,BC109 9p ea DIL IC's BOARDS 6x41" 11.50
723 Regulator67p 2E3055 39p Three for 11 24 way edge connector 60p
JUMBO LED 0.6" NE531 35V/us 12 11511/T03 or 90W plastic
0-9DP 12.25 ea 741 TO99 29p NE536 FET OPA12 36way 90p. PLAIN 31.x17 11
741 DIL8 31p NE540 Driver il 253819E 16p 253053 17p
FACE CUTTER 43p. FEC ETCHANT
LIQUID CRYSTAL
6 digit 118
741 DIL14 31p
747 Dual 741 89p
748 DIL 8
1505 IC A/D
36p
NE546 AM Rx11.50
NE550 2v ref 79p
NE555 TIMER 67p
BFY50/51/52/53 all 18p
1A50Vrect 4p ea 15914 4PI
Price each:-
Saillpeneep
PRINTED CIRCUIT BOARD KIT 11:69

LED I4P.
MINI PIN SOURCE OR RED DIFFUSE
Converter 17
7805 1A5V 11.59
7808 1A8V 11.69
NESS6
NE560
NE561
Dual."11.30
PLL
PLL
13.15
13.15
AC127/128 16p
AC187/188 19p
AD161/162 35p
TIP2955
TIP3055
90p COPPER BOARD 6x4" 40p.
55p DESOLDER BRAID reel 59p
TIS43 UJT'25p HEATSINKS
NE562 PLL 13.19 BC107/8/9 9p IN4001
LEDS.209 STYLE.NO CLIP. 14P ea 7812 1Al2V 11.69 5f/T05 & 18f/T018 5p ea.
7815 IA15V 11.69 NE565 PLL 12.69 BC132/4/7 18p IN4004
TIL209 RED LED & CLIP 17P ea 76009 IW AF 75p NE566 Gen 12.49 BC147/8/9 10p 154148/914 4p TV4 12p.TV3/T03 16p.4YI/T03 29p.
BC157/8/9 12p
BIG I" RED LED & CLIP 18P ea 76013 6W AF11.39
8038 Sig Gen 13
NE567 code 12.69
SN72709 709 29p BC167/8/9 12p
2N697
25706/8
13p
10p CAPACITORS
ORANGE & GREEN LEDS: SN72741 741 31p BCI77/8/9 18p 252646 49p 22pf to 0.1uf 4p ea.ELECTROLYTIC
CA3046 69p SN72748 748 36p BC182/3/411p 252904/5 20p 25V 2/10/50/100uf 6p.1000uf 20p
MINI 25P ea.BIG & CLIP 33P ea LM301 OPA 49p
SN76131 /1.20 BC212/3/4.12p 252926royg 9p PRESETS VERT:5p.RESISTORS5t lIp
INFRA RED LED 11.255777 33P. LM307 OPA 49p A or L 2E3053 17p
LM308 HiBoPa 95p SN76660 PELF 11
PS12 PHOTO IC/amp/switch it.
L14309K Reg.12.29 SN76611 IF 11.25
TAD loo & IF 12
BCY70/1/2 15p
BD131/2 39p
2E3055
253614
39p
49p POTS ABor EGIN
OIGITfil CLOCIi LM371

LM373
RF/IF 12
LM3725 AF/IF 12
13
25400E
25402T
13
11.75
BFY50/1/2 18p
BFY53 17p
2E3702/3 9p ROTARY:12p.SWITCH 13p.DUAL 38p.
2E3704/5 10p SLIDERS:SINGLE 26p.DOUBLE 48p.
MOS INTEGRATED CIRCUITS. BSX20 12p 253706/7 9p
LM377 202W 12.69 ZN403 Servo/2.50
AY51224 4 DIGIT CLOCK supplied
LM380 2W AF 99p
MJE2955 95p 213708/9 BP SWITCHES:SPST 18p.DPDT 25p.
with 14pin socket & data 14.25 25414 AM Rx11.09 MJE3055 62p 253710/11 9P MINI I":SPST 39p.PUSH 39p.
1.14381)2xpre.12 MPU131put 49p
MM5311/14 6 DIGIT CLOCK with LM382)amp 253563/64 16p BENCH POWER SUPPLY 3-12V 15.
12
28 pin socket & data
3IDIGIT DVM AY53500
17.50
17.50
1E3900 4x0PA 69p1 1411 TTL 0A91
TIP29A
TIP30A
8p
48p
57p
253566/67 16p DIN PLUGS all 13p ea.Sockets 9p
253638 16p
TRANSFORMERS IA 6/12V 11.34
14C1303 11.20 7400 etc gates 16p 253641/2 16p
4DIGIT COUNTER/DRIVER 17.50 TIP31A 61p 253819E lip BHA 0002 MODULE 15WATT AMP 15
MC1306 49p 7413 schmitt 31p TIP32A EA1000 4W AF MODULE
73p 253832E 17p 12.49
MC1310 & LED 12.69 7447 driver 11.09 TIP41A
CASSETTE MC1312 SQamp 52.50 7470/72 32p TIP42A
78p
89p
253904/6 14p 8W/12V FLUORESCENT LIGHT 13.

mischanicse12.5 0MC1330
MC1339
69p
11
7473/74/76
7475
39p
48p BZY88 400mW
2N4249 16P
TAG 1/400 55P
OIL sockets
STEREO CASSETTE MECHANISM. MC1350 55p 7490 Counter 63p ZENERS 9p C107D1 SCR PROFESSIONAL
MC1351 71p 7492 Counter 69p BRIDGE RECT 4A/400V 55p COLD PLATED
As used in imported types MC1352 74121 mono 45p IA 50V 20p GREY NYLON.
costing 1100.0nly requires MC1357 11P 74141 driver 83p
GAS SENSOR 12 SC146D TRIAC 8,14 or 16 PIN
a case & electronics.Heads MC1358 11
ONLY 15p each.
supplied.Send for data 15p. MC1375 1145 Full range in Cat.. GAS " KIT 15 10A 400V 75p

Practical Electronics January 1975 77

Forward with Project 80 into

Everything you want in one pack

to build the world's most
advanced modular hi-fi
This is Project 80 made
WITHOUT SOLDERING

1 Stereo 80 Control Unit

even easier to build
For mag.-and ceramic cartridges, radio You have seen how the marvellously compact Project 80 modules ( only 2" high x
and tape. deep) are so adaptable and easy to install. Now, with Project 805, this wonderful
system is made easier still to put together. In this, you have not only all the Project 80
2 Project 80 power amplifiers modules in one pack for building an 8/8 watt R.M.S. hi-fi amplifier - there is also a
Two Z.40s to give 8/8 watts R M.S. loom of colour coded wires cut to lengthand tagged forclipping on so that you don't even
output per channel. have to solder! Input and output connections go via the 805 Masterlink panel. With the
3 Power supply unit explicit stage -by -stage large 32 page instructions manual included, it becomes easy for
One PZ.5. anyone, no matter how inexperienced to install an ultra -modern assembly so advanced in
appearance and design that it sets brand new concepts in domestic hi-fi - and of course,
4 Connecting wires you can convert to quadraphony just whenever you wish by adding 805S0. Only Sinclair
All wires plus nuts, bolts, screws etc. know-how and manufacturing facilities could hope to bring you such quality and versatility.
5 Project 805 Masterlink
For input and output connections.
6 Mains switch block and instructions TAGGED WIRES CUT TO LENGTHNO SOLDERING
manual (not illustrated).

Project 805
the complete ready-tobuild hi-fi
STEREO AMPLIFIER
Project 805 comprises a Stereo 80 Pre-amp/Control
Unit with input for both magnetic and ceramic
cartridges, radio, tape; separate bass and treble cut/
lift, and volume controls 2 x Z.40 power amplifiers,
PZ.5 power unit, 805 Masterlink, wire loom, instruc-
tions manual, etc. down to nuts, bolts and washers.
For technical specifications, see third page of this
advertisement.
£39.95 +f3.20 VAT (R.R.P.)

SINCLAIR RADIONICS LTD

London Rd, St. Ives, Huntingdon PE17 4HJ
Telephone St. Ives (0480) 64646
 true quadraphonics... NOW!
The most effective and
economical way to enjoy
this spectacular break-
through in hifi listening

1. Project 80SQ decoder with controls.

2. Two Z.40 power amplifiers.
3. PZ.5 power pack
4. Project 80Q Masterlink unit.
5 Wire loom, with clip -on tags- NO SOLDERING I
6. (Not illustrated) Instructions manual, nuts bolts, washers, etc.

Add a fourth dimension

to your stereo sound
It's so simple to convert to quadraphonics when you already have Project 80, or are about Frequency response 3db 15 Hz-25kHz
to start with Project 805. Project 805SQ is a complete add-on system at the heart of which
Rated output 100mV
is the Project 80SQ decoder. It uses the CBS.SQ matrix principle, by now the widest used
method of containing four sound channels within the groove of the record. Project 805SQ S/N ratio 58dB
includes two power amplifiers, power supply unit, connecting wire loom, 805Q Master -
link, switch block and instructions manual. The 80SQ decoder (also obtainable separately) Distortion 0-1%
has independent tone and volume slider controls on the two rear channels for matching Power requirements 22-35 volts
true four channel sound to domestic environment. Project 805SQ is money saving too
since you do not have to scrap existing Project 80 equipment to enjoy the newest and most Phase shift network 90° i10:'100 Hz-10kHz
exciting form of home listening in the entire history of sound, and your Project 80 quad- Adaptable to discrete (C D4) use
raphonic assembly is compatible with stereo and mono records.

Project 805SQ
Link to
Tape In/Out
Speakers: 0

Four channel
AUDIO
SO Input AREA
Elj

rh SO Decoder Rear
Stereo 80
Speakers

Power unit Power unit

The output from any good stereo cartridge feeds into Stereo 80 and
passes via the tape outlet to the 80SQ decoder. Here the signal is
separated into its constituent 4 channels, those for the front being
accepted by the Stereo 80, those for the rear going from the
decoder to the two additional power amplifiers and speakers.
£44.95 +E3.60 VAT (R.R.P.)

If, within 3 months of purchasing any product direct from us, Project 80 quadraphonic modules may be purchased separately if
Guarantee you are dissatisfied with it, your money will be refunded on required. The Project 80SQ decoder may be used with any other
production of receipt of payment. Many Sinclair Appointed Stockists also offer this
guarantee Should any defect arise in normal use within 2 years, we will service it amplifier havingtape and monitoring facilities. Z40 or Z60
without charge. For damage arising from mis-use a nominal charge wit be made. power amps can be used as required.
 he Project 80 programme to date
KEEP THIS PAGE FOR HANDY REFERENCE USE THE PRIORITY ORDER FORM IN CASES OF DIFFICULTY
Stereo 80 pre-amp/control unit 2.60
Size - 55 98. 20mm
12 transistors
:III 111111 I Mil I 1111 11111
Input sensitivity - 100- 250mV
Output - 25 watts R MS
continuous into 8 0 (50V).
III II I III I 1111111111 Distortion - 0.02% at 10W/8 0/1 KHz
Frequency response -10Hz to more than 200KHz ± 3dB
260x 50A 20mm (10-1x 2 x I ins.) separate slider controls on each S/N ratio - better than 70dB
channel for treble, bass and volume INPUTS - Mag. P.0 3mV (RIAA Built-in protection against transient overload and short circuiting
corrected) ceramic - 300mV. Radio 100mV, Tape 30mV S/N ratio 60dB. Load impedance - 4 0 min; max. safe on open circuit
Frequency range - 20Hz to 15KHz ± 1dB OUTPUTS - 2-5V rms max
(30V. supply) and tape plus AB monitoring PRESS BUTTONS for P.U., £7.45 + 60p
VAT (R R P
Radio and Tape Operating power - 20 to 35V Black case with white
,ndications Power -supply units
£13.95 f 1 12
VAT (R R P )
PZ.5 Unstabilized. 30 volts. Suitable
Project 80 F.M. tuner for Z.40 assemblies, etc. £5.95 +48P
VAT (R R
U6 NIX 0111E6
PZ.6 Stabilized. Output voltage ad-
11111111 justable between 20 and 50
£8.95
11 72p
volts approx. Protecting fuse. VAT (R R P
111 (1.1. 1111111
MntO
PZ.8 Stabilized. Output adjustable
Size 85x 50 x 20mm (3i), 2x I ins.). Tunes 87-5 to 108MHz. DE- from 20 to 60V. approx Re-
TECTOR - I.0 balanced coincidence (I.0 equivalent to 26 transistors) entrant current limiting makes
Distortion - 0.2% at 1 KHz for 30% modulation. SENSITIVITY - 5 damage from overload or even
microvolts for 30dB quieting. Output - 300mV for 30% modulation shorting, impossible. Without
Aerial imp. - 75 0 or 240-300 0. Dual Varicao tuning. 4 pole ceramic mains transformer.
filter. Switchable A.F.C. Operating power 23-30 volts.
El 12
£8.45 + 68p
VAT (R. R P.)

£13.95 VAT (R. R.P

Project 805 (previous pages) £39.95 VAT R?(2°R P

Project 80 stereo decoder
Size 47x 50> 20mm For adding to Project
80 FM tuner. With one I C equal to 19 tran- Project 805SQ quadraphonic
sistors. and LED indicator which glows on add-on kit £44.95 VAT(.0R P
tuning in stereo signal.

£8.95 + 72p
VAT (R R P.)
Project 80SQ quadraphonic decoder
Project 80 active filter unit
(A.F.U.) 1111 III III

III F 1III -111 1111

Size 108+ 50 \ 20mm. Useful where there is need to eliminate unwanted Size 260 50 20mm, matching Stereo 80 in style. Connects with tape
high frequencies (scratch, whistle, etc) or low (rumble). Voltage gain - socket on stereo 80 or similar facility on any stereo amplifier. Frequency
minus 0.2dB. Frequency response (filter at zero) 36Hz to 22KHz. H.F response 15Hz to 25KHz + 3dB. Distortion 01%. S/N ratio 58dB,
cut (scratch) variable from 22KHz to 5 5KHz 12dB/octave slope. L.F Rated Output - 100mV. Separate bass and treble slider controls on each
cut (rumble) - 28dB at 28Hz, slope 9dB/octave. + 60p channel, also volume. Phase shift network 90 ± 10, 100Hz to 10KHz.
£7.45 VAT (R.R.P.) Operating power - 22-35V. +0.52
Project 80 power amplifiers
£18.95 VAT (R.R. P.)

Intended for use in Project 80 installations, these modules readily adapt Sinclair Q.16 loudspeaker
to an even wider range of applications. Both incorporate built-in protec-
tion against short circuiting and risk of damage from mis-use is greatly An original and uniquely designed
reduced speaker of outstanding efficiency.
Z.40 Balanced sealed sound chamber
Size 55 x 80 20mm and special driver assembly. Loads
9 transistors up to 14 W./R M.S. 8 ohms imp.
Input sensitivity - 100mV Size 248mm square x 120mm
Output - 12 watts R MS continuous into .8 0 (35v) deep. Pedestal base. All-over
Frequency response - 10Hz - 100KHz ± 1dB black front, teak surround.
Si N ratio - 64dB
Distortion - 0-1% at 10 watts into 8 0 at 1 KHz c 48+ £8.95 + 72p
VAT (R R P
Power requirements - 12 to 35 volts u VAT (R R P I

USE THIS PRIORITY ORDER FORM IN CASES OF DIFFICULTY

SiniIair
Sinclair Radionics Ltd.,
To Sinclair Radionics Ltd.
Please send, (carriage paid in U.K.) NAME

London Road St. Ives ADDRESS

Huntingdonshire PE17 4HJ
Telephone St. Ives (0480) 64311 ...
R.O. St. Ives: Reg No. 6994583 Eng. For which I enclose E cash/
cheque/money order INCLUDING V.A.T. PE175

80 Practical Electronics January 1975

 PHONOSONICS SUPPLIERS OF QUALITY PRINTED
CIRCUIT BOARDS, KITS AND
COMPONENTS TO A WORLD-WIDE MARKET

SOUND -TO -LIGHT PHASING UNIT SOUND BENDER

The ever -popular AURORA -4 or 8 channels each A simple but effective manually controlled unit for A multi -purpose sound controller, the functions of which
responding to a different sound frequency and atop - introducing the "phasing" sound Into live or recorded include envelope shaper, tremolo. voice operated fader.
trolling its own light. Can be used with most audio music. automatic fader and frequency doubler.
systems and lamp intensities. A must for any Disco, 02.20 £503
and a fascinating visual display for the home. Component set (incl. PCB) Component set
Printed circuit board 01.44
4 channel component set (excl. thyristors) £11.49
8 channel component set (excl. thyristors) [20.32 P.E. SOUND SYNTHESISER
Power supply component set £/ 78 The well -acclaimed and highly versatile Synthesiser REVERBERATION UNIT
PCB for 4 frequency channels £2.50 published in P.E. Feb. 1973 to Feb. 1974. A high -quality unit having microphone and line input
PCB for power supply and 8 lamp drivers CI .25 pre -amps. and providing full control over reverberation
Component sets and printed circuit boards: Full details level.
in list.
Component set (en! spring unit) 0144
P.E. CCTV CAMERA RHYTHM GENERATOR
Printed circuit board t1.40

Details in List Programmable for 64.000 rhythm patterns from 8 effects

circuits (high and low bongos, bass and snare drums,
long and short brushes, blocks and cymbal). and with
VOICE OPERATED FADER variable time signatures. P.E. MINISONIC
automatically reducing music volume during
For
"talk -over" -particularly useful for Disco work. or for Tempo, Timing and Logic artuft
Component set (excl. switches) [17.25 Details in List
home -movie shows. Double -sided PCB for above 02.30
Component set, incl. PCB £2.88
Miser, Pre -amp end Effects Circuits
Component set 02.70
P.E. GEMINI 30W STEREO AMPLIFIER PCB (illustrated) 02'07 8W AMPLIFIER
An exceptionally high quality Stereo Amplifier system, Monitor Amplifier A moderately powered amplifier of more than average
Component set and PCB 03.10 performance.
specifications for which are shown In detail in our list.
together with semiconductor requirements. Power Supply
Component set and PCB 0565 Main Amplifier
Main Amplifier Mono component set 01.18
Set Of resistors, capacitors and presets £5.98 Stereo component set u 38
Stereo printed Circuit board C1 28 Mono printed circuit board 72p
Pre -Amplifier: Pre-Amplifler
Sets of resistors. capacitors, potentiometers Mono component set £2.50
and switches - Stereo component set £6.49
Standard Tolerance Set £10-57 Stereo PCB £1.116
Superior Tolerance Set £16 04 Power Supply
Stereo PCB (es Published) £2.20 Component set £3.90
Regulated Power Supply:
Set of resistors, capacitors and preset C/-58
Printed circuit board 72p BIOLOGICAL AMPLIFIER
Multi -function circuits that, with the use of other external
equipment. can serve as lie detector, alphaphone.
HI-FI TAPE LINK cardlophone. etc.
Designed for use with reasonable quality tape decks.
this high performance pre -amp Includes record, playback Pre -Amplifier Module
and metering circuits. Component set and PCB 2348
41 211Atj' Basic Output CIrcuffs
Stereo component set (excl. panel meter)
Mono component set (excl. panel meter)
Power supply component set
Stereo main
E2205
£1331
C372
L250
VI -*It /PAIL Combined component set with PCBs, for alpha -
phone, cardiophone, frequency meter and visual
feed -back lamp driver circuits
Audio Amplifier Module
01.96
Stereo sub -assembly PCB 86p
'4013 Type PC7 C520

TAPE -NOISE LIMITER PHOTOPRINT PROCESS CONTROL

Very effective circuit for reducing the hiss found in most For colour and B 8 W. an indespensible dark -room unit
tape recordings. for finding exposure. controlling enlarger timing, and
Component set (incl. PCB) C230 AUDIO MILLIVOLTMETER stabilising mains voltage.
Regulated power supply (including printed circuit WIde-renges and good accuracy. Component Component set (excl. meter) ell115
board) £3.71 set (excl. meter) while stocks last £523 Printed circuit board 01.00

PROJECT 04 ULTRASONIC TRANSMITTER -RECEIVER

Multi -system Quadraphonic Decoder. ENLARGER EXPOSURE
A highly sensitive and long range invisible beam METER AND THERMOMETER
£13.74 detection circuit with numerous applications.
Decoder component set
Power supply components £3.22 Dual-purpose dark -room unit with good accuracy.
£2.60 Component set with PCBs, but excluding trans-
Set of PCBs ducers £4.40
Component set with PCB, but excluding meter £4.00
SEMICONDUCTOR TESTER POWER SLAVES
Essential test equipment for the enterprising home P.E. RONDO
constructor. PCB details in List. PCB details in List. WIND AND RAIN UNIT
A manually controlled unit for producing the above -named
sounds.
Set of resistors. capacitors, semiconductors.
potentiometers, makaswitches and sub -assembly P.E. ELECTRONIC PIANO HOME INTERCOM
Details in List. Details in List. Component set incl. PCB £2.40
PCB (fuller details in lis ) £11.011

OVERSEAS
PCB LAYOUT AND VAT LIST P. 8. P. will be charged at cost.
COLOUR CODE
CIRCUIT DIAGRAMS Add 8% (or current Send S.A.E. for free list VAT does not currently apply. List IDENTIFICATION
SUPPLIED WITH ALL
P. 8 P. rate different) to
if giving fulle details of SUPPLIED WITH MOST
Add 18p to all orders gives fuller details including kit
PCBs DESIGNED BY total order cost in- kits. PCBs, and other weights. Charge for list: Europe KITS AND AS PART OF
PHONOSONICS eluding P. & P. components 10p, other countries 20p. LIST

Semiconductors - integrated Circuits Polyester Tantalum

IbFIV)
(en

5 63V34111
AC128 20p MJE30 5 TSp 253823E 3ep 709 705 40p Electrolytic Capacitors (eFIV)
AC176 29p NICT0033 112p 2494870 36p 723 705 asp Zemin 0.01 3p 1/35 12p
°Cal 65p 2N4871 20p 741 &pin DIL 0 47.63V Sp 47/63 470,40 200 0.015 -22/35 12p
BC107 13p 400 3.3V 400mW 12p 7111
3p
BC108 13p 0071 14p 2495777 45p 747 14p1n OIL 115P 4.7V 1W 25p
1 0 63V b 50/6 4 SP 500/64 MP 0 022 3p .47/ 35 12p
0081 25p 718 TOS 53p Op 100/10 Op 680/6.3 0.033 lap
5.6V 1.3w 20p17 .0/35 12
1
BC109 13p 20p 1

ORP12 55p Diodes 741I 8-pIn DIL 1 2 63V Op 100/25 110 680/25 0.047 5/35 129
BC147 12p OP 6.2V 400mW 159 Sp 100/40
34P
13C148 12p IT2107 12P 1N914 4, 71001/ -pin DIL
718 B30 9.1v momw me 4 7 53
6-8 40 ap 10043
7P 680,40 2M oats 30 2 35
12p 215503 15p 7100 12P 1000/10 119 0.1 4p 12p
BC149 IIV 1W 7 35
"
1741001 app 20P 20p Sp 150/18
BC157 ' 13p
13p
ZTX531
211706
2312
tap
1N4002 7.
.; '
7402
7420
n 12V 100mW 15p
2
10/25
10,63 Sp 150/63
IP
120
1000/16
1000/25
25po
219
0.15
0.22
i
5o 0.16 lap
BC158 12V 1.3W 0/25 p
BC159 tap 249911 .4.,
1N40134
1494005 i;il; 7447
200
175p toy 400mW 15P
15/43
22/10
00 220/10
Sp 220/16
Op
lie
1000/10
2200/25
lap
Me
0.33
5.47
50
7p 5/6.3 16p
lap
12p 2N1304 22P tope 7473 44P 18V 1W 200 OP 22/16
up 282219 27p 22/25 Sp 220/25 100 2200/40 Ilp 7/6.3 16p
BCIS2L
204
BC209c
BC212L
14p
15p
2N2905
282907
27p
22p
BA145
0091
0A2,
230
7p
Sp
7189
u/47815 103
IA7815 70220
5750
250p
Seep
20V 100mW
20V 1 3W
27V 100mW
15p
230
15p
.,.
33/8-3
--
11p 220/40
Sp 220/63
140
21p
2800/100
3300/63
511P
350p
133P
0.68
1.0
2.2
lap
sap
7/16V
00/3
25p
16p
BC178 a, 2713054 3110 1G P7 12, CA3046 1190 31/40
33/50
Sp
Ilp
330170
470/6.3
flo 3300/100 350p
BCY71 22p 283055 SOP 1SJ50 lip MFC8010 9SP Thyffstors IP sap
BP/50 22p 2493702 12p zu up PA263 1611p
lA 400V 75p
47/25
47,40
111p 170/10 10p 4700,25
4700/25
75P PRICES ARE CORRECT AT TIME OF
BFY52 230 283703 12p SG310274 169p ap 470/25 11p 4700/40 93p
PRESS. E. & O.E. DELIVERIES
BSY95A 12e 2N3704 12p
Minilron 3015F 225p
SUBJECT TO AVAILABILITY.
MJE2555 1190 2493819 35p

PHONOSONICS, DEPT. PE2D, 25 KENTISH ROAD, BELVEDERE, KENT DA17 5BW

MAIL ORDER ONLY
81
Practical Electronics January 1975
 I.L.P. (Electronics) Ltd
SHEER SIMPLICITY! BASS
Tape o.p
Tuner
Gram 0-
Tape 0
Fuse
Half HY5 Half HY5 HY50

L.S

-0
-r0
0-
0 TREBLE
4- 41- BALANCE
VOLUME

Stereo.Mono switch

-L
PSU511
-N
Oe
-E
MONO ELECTRICAL CIRCUIT DIAGRAM WITH INTERCONNECTIONS FOR STEREO SHOWN

The HY5 rs a complete mono hybrid preamplifier. ideally The HY50 is a complete solid state hybrid Hi-Fi amplifier
suited for both mono and stereo applications. Internally incorporsting its own high conductivity heatsink her-
the device consists of two high quality amplifiers-the metically sealed in black epoxy resin. Only five connections
first contains frequency equalisation and gain correction, are provided. input. output, power lines and earth.
while the second caters for tone control and balance.
TECHNICAL SPECIFICATION
TECHNICAL SPECIFICATION Output Power: 25W RMS into 8kf1. Load Impedance:
Inputs: Magnetic Pick-up 3mV RIM: Ceramic Pick-up 4-16kn. Input Sensitivity 0db (0,775V FNS). Input
30mV. Microphone 10mV. Tuner 100mV, Auxiliary 3-100mV, Impedance 4711(1. Distortion: Less than 0 1% at 25W
Input/impedance 47kfl at IkHz. Outputs: Tape 100mV: typically 0.05%. Signal/Noise Ratio: Better than 75db
Main output Odb (0 775V RMS). Active Tone Control.: Frequency Response: 10Hz-50kHz , 3db Supply Volteg. The PSU50 can be used for either mono or stereo sVatilin1a.
Treble It 12db at 10kHz; Bass ,12db at 100Hz Distortion: 25V Siva: 105 - 50 25mm
0 5% at IkHz. SIgnI/Nolse Rollo: 68db. Overload Capa- TECHNICAL SPECIFICATIONS
bility: 4000 on most sensitive input. Supply Voltage,: + 48p VAT Output voltage- z 25V. Input voltage: 210-240V Size: L 70
_16-25V PRICE £5.98 P P. tree D.90.H 60mm

- 35p VAT
PRICE £4.50 P & P free PRICE £5
TWO YEARS' GUARANTEE ON ALL OUR PRODUCTS
Please Supply
I.L.P. Electronics Ltd.
Total Purchase Price
Crossland House, I Enclose Cheque 0 Postal Orders 0 Money Order 0
Please debit my Access account 0 Barclaycard account El
Nackington, Canterbury, Account number
Kent CT4 7AD. Name and Address
Tel (0227) 63218 Signature

82 Practical Electronics January 1975

 GIRO NO. 331 7056 SPECIAL RESISTOR KITS (Prices include Post and Packing).
C.W.O. only. P. & P. 10p on orders below C5 10E12 I -W KIT: 10 of each E12 value, 22 ohms-IM, a total of 570 (CARBON FILM 5%). 13.65 net
Discount: L10-10%, L20-IS",, (except net items) 10E12 3W KIT: 10 of each E12 value, 22 ohms-IM, a total of 570 (CARBON FILM 5%). 1345 net
Export Order enquiries welcome (VAT free) 25E12 IW KIT: 25 of each EI2 value, 22 ohms-I M. a total of 1425 (CARBON FILM 5%). 01.35 net
25E12 3W KIT: 25 of each E12 value. 22 ohms-I M, a total of 1425 (CARBON FILM 5%). £5.45 net
Official Orders accepted from 5E12 1W KIT: 5 of each E12 value. 10 ohms-IM, a total of 305 (METAL FILM 5%), f.2.115 net
Educational & Government Departments PLEASE NOTE: DUE TO CURRENT WORLD SHORTAGES THESE KITS MAY TEMPORARILY
ALL PRICES INCLUDE VAT CONTAIN BOTH WATTAGE AND VALUE SUBSTITUTIONS.
MULLARD POLYESTER CAPACITORS C210 SERIES RESISTORS
CF-High Stab Carbon Film, 5%. MF-High Stab Metal Film, 5%.

I SAF, 23p. 2.2µF, 26p.CF

250V P.C. Mounting: 001,./F, 0-015AF, 0.022AF, 0.033µF, 0047AF, 33p. 0.0680F, W. Type Range 1-99 100-499 500-999 1000+ Size mm
0-1AF, 4Ip. 0-15AF, 49p. 0.22AF, 5Ip. 0-33µF, Sp. 0.47AF, 9p. 0.68AF, 11p, IAF, 0.75 0.60 0.55 2.4 x 7.5
15p. CF 22-2M2 I 0.75 060 0.55 3.9 x 10.5
MULLARD POLYESTER CAPACITORS 0296 SERIES 3 CF 22 -IM 0.75 0.60 0.55 55 x 16
400V, 0.00IAF, 0.0015µF, 0.0022AF, 0.0033AF, 23p. 0.0047AF, 3p. 0.0068AF, 0.01µF, MF 10-2M7 2
I

1.54 1.32 I1 3x7

0.015µF, 022AF, 0.033AF, 3fp. 0.047AF, 0.068µF, 0.14F, 49p. 0. 15µF, 69p. 022AF, k
I MF 10-2M2 2 1.43 I 2I 0.99 4.2 x 10.8
119p. 033µF, 12p. 0.47AF, 14p. MF 10 -IOM 3 1.98 i-ei 1:65 6.6 x 18
160V: 0.01AF, 0.015AF, 002AF, 3p. 0.047µF, 0.066AF. 33p. 0.IAF, 4Ip. O. 15µF, Sp. 1

10-10M 4'5 3.52 3.08 2.75 8 x 17:5

022AF. 53p. 033µF, 63p. 0.47pF, Sip. 0.68AF. 12p. 11.1F, 14p. For value mixing prices, please refer to our catalogue (price ,n pence each).
MINIATURE CERAMIC PLATE CAPACITORS VALUES AVAILABLE-E12 Series only. Net prices above 100.
50V: (pF) 22, 27, 33, 39, 47, 56, 68, 82. 100. 120, 150, ISO, 220, 270. 330. 390. 470,
560, 680, 820. 1K, I K5, 2K2, 3K3, 4K7, 6K8, (AF.) 0-01, 0-015, 0:02. 0-033, 0:047, PRESET SKELETON POTENTIOMETERS Wavechange Switches
IP, 4W; IP, I2W; 2P,
29p each. 0.1, 30V, 43p. MINIATURE 0-25W Vertical or horizontal 6p each 2W; 2P, 4W; 2P, 6W;
POLYSTYRENE CAPACITORS 160V 5%. 1K, 2K2, 4K7, 10K, etc. up to IMO 3W; 4P, 2W; 3P,
(pF) 10, 15, 22, 33, 47, 68, 100, 150, 220, 330, 470, 680, 1000, 1500, 2200, 3300, 3P
4700, 10.000, Alp. SUB -MIN. 0.05W Vertical. 1000 to 220K0 Sp each 4W; 4P, 3W, 30p

B. H. COMPONENT FACTORS LTD Tel.: Cheddington

(t:itE.1-11 11:1`3Pc.):668446 (Std. Code 0296)
'18.1211RIO:1)617177°4
CATALOGUE No. 3 20p.
2'

VEROBOARD 0I 0.15 POTENTIOMETERS

Miniature Mull rd Electronics 5' 36p 36p Carbon Track 5K0 to 2M0, log or lin. Single. 163p. Dual Gang 46p. Log Single with
33p 15p Switch 16p. Slider Pots, 10K, 100K, 500K. 30mm, 34p. 45mm, 47p. 60mm, 55p.
10µF 63V 6 68AF 16V 69 p ,3!'
I :5µF 63V 6 68AF 63V Ilp
2, i
"z
34
'
33"
42p 46p
36p 36p DIODES PLUGS ELECTROLYTIC CAPACITORS. Tubular & Large Cans
22AF 63V 100AF IOV 60 DIN 2 Pin lip (AF/V): 1/25, 2/25, 4/25. 4.7/10, 5/25, 8/25, 10/10, 10/50, 16/25,
-- 16p
6
33AF 63V 6 100AF 25V 61D 23 I. 9 90 N4001 6 p 3 Pin 130 22/63 25/25 25/50 32/25. 50/25. 100/10, 100/25, 69p. 50/50, Sp.
4.0AF 40V 6 100µF 63V 14p 24 5' (Plain) 90 N1002 7}p S Pin 180' 16 / ' 200,25 II. 50/21 p. 500/10, Ilp 500/25, 15p
250'50,
4.7AF 63V 6 150AF I6V 63p 31. (Plain) N4003 P Std lack 20; 51 0000400: lap./ 1000/1P0, 15p.' 1000/25, 12p. 1000/50, 40p. 2000/10.,
6.8AF 63V 6 150µF 63V 15p 5 ' 31" (Plain)
Insertion tool
- 29P
73p
N4004 93p 2.5mm
'
lack 1317 20p. 1000/100. 90p. 2000/25, 30p. 2000/100, 95p. 2500/25, 311p.
80µF 40V 6 220AF 6-4V6Ip 73111 N4005 12p Phono 6p 2500/50, 61p. 3000/50, 130p. 5000/25, 66p. 5000/50, [1 .10.
10AF 25V 220AF IOV 61p Track Cutter 56p 56P N4006 14p
6
Pins. Pkt. 50 22p 22p HI -VOLT: 8/350, 19p. 16/350. 22p. 32/350. 33p. 50/250, 10p.
10µF 63V 6 2204F 16V N914 7p SOCKETS 100/100, 10p. 100/250, 30p. 4/450 14p. 16/450 23p.
15AF 16V 6 220AF 63V 21p N916 7p DIN 2 Pin 10p
150F 63V 6 330AF 16V lip TRANSISTORS BA100 10p 3 Pin 10p METALLISED PAPER CAPACITORS
16AF 40V 6 330AF 63V 25p OAS 42p 5 Pin ISOI2p 250V: 0.05AF, 0.IAF, 6p. 0:25, 6p. 0.5µF, 73p. 1HF, 9p. I

224F 25V 6 470 AF 6.4V 9p ACI26 163p BC2I2L 2p 0A47 9p Std. Jack15p 500V: 0-025, 0.05, 6p. 0.1, 6p. 0.25, 70.0-5, 9p.
22AF 63V 6 470AF 40V 20p ACI28 22p BC213L 2p 0A81 I 1p
2,5rnrn Jack 13p 1000V: 0.01, I ip. 0-022, 13p. 0.047, 0.1, 15p. 022, 23p. 047,
32AF IOV 6 61100F I6V 15p BC107 I 1p BC214L 7p 0A200 BD Phono 6p 28p.
33AF I6V 6 680AF 40V 25p BC108 12p 0C44 8p
63p NEW CAPACITOR KITS
33AF 40V 1000AF I 6V 2.0p BC109 13p 0071 3p Integrated Screened Wire, Metre
6
.., 1000AF 25V 3.5p BC148 12p 0081 6p Circuits Twin Screened Wire, Metre Ilp - Please send for List
32µF 63V 6
''' 1500µF64 15p BCI49 12p 0C170 2.3p 0A709C 50p Stereo Screened Wire, Metre 12p
47µF IOV 6p 1500µF 16V 25p BC I82L 12p TIS43 33p AA74IC 55p Connecting Wire, All colours, Metre 2Ip NOTE: ALL STOCK ADVER-
47µF 25V 6 12 2200AF IOV 25p BCI83L 11p 2N2926 I 1p AA723C II Neon Bulb, 90V Wire Ended 5 for 24p TISED IS SUBJECT TO
47ttF 63V 6p 3300µF64 26p BC I84L 13p 2N3702 I 1p ZN414 LIM Panel Neon, 240V. Red, Amber, Clear 163p AVAILABILITY

The Pictorial Method ELECTRICITY(5vols)

BAST You'll find it easy to learn with this outstandingly
ELECTRONICS(6vols)
TELEVISION(3vols)
GUARANTEE
successful PICTORIAL METHOD. The essential facts Should you be, in
are explained in the simplest language, one at a time, any way dissatis-
and each is illustrated by an accurate cartoon -type fied with the
drawing. These clear and concise illustrations make MANUALS your
study a real pleasure. The books are based on the latest money will be re-
research into simplified learning techniques. This easy - funded by return
approach -to -learning method has proved beyond doubt of post.
that acquiring knowledge can be an enjoyable ex-
perience.
The eerie.
will be of isx
ceptional value In
training mechanics and
r To The SELRAY BOOK CO., 60 HAYES HILL, HAYES,
BROMLEY, KENT. BR2 7HP
11

technicians In Electricity,
WHAT READERS SAY Radio and Electronics. Please find enclosed P.O./Cheque value £
At such a low cost they are a magnificent set of books. BASIC ELECTRICITY 5 parts £6.50 El
W.I.. Ladywell BASIC ELECTRONICS 6 parts £7.50 CI
My sincere congratulations on describing everything BASIC TELEVISION 3 parts £4.25 E
so simply. J.B.. Belford Prices include Postage
Tick Set(s) required.
have received both enlightenment and pleasure
I

from reading your manuals. VS.. Huddersfield YOUR 100% GUARANTEE. If after 10 days examination you decide to
I am very satisfied with (hese carefully written and return the Manuals your money will be refunded in full.
well expressed manuals. A. W.. Sandown
NAME
They are concise and easily understood and I agree BLOCK LETTERS
with everything that other readers have said in their
favour. W. W.. Stockton FULL POSTAL
Expressing my great delight with your excellent ADDRESS
manual, S S Paddington

83
Practical Electronics January 1975
 12In LONG PERSISTENCE CRT. Full TRIMMER PACK. 2 twin 5112043pF
spec. Price 0650 to include V.A.T. and ceramic. 2 twin 113/60pF ceramic, 2 min
strip with 4 preset 5/20pF on each; 3 air

FERRANTI
Carriage.
spaced prism 30/1013pF on ceramic base
MAKE YOUR SINGLE BEAM SCOPE ALL BRAND NEW. ISp the lot. P. 6 P.
INTO A DOUBLE WITH OUR NEW LOW 10p.
PRICED SOLID STATE SWITCH. 2Hz to
13MHz. Hook up to a 9 volt battery and PHOTOCELL equ. OCP71. 13p each.
* ALL DEVICES BRAND NEW, TOP GRADE AND TO connect to your scope and have two MULLARD OCP70, 10p each
FULL MANUFACTURERS SPECIFICATION. We do traces for ONLY 06.25, P. 8 P. 25p (Not
not sell seconds or rejects. cased. not calibrated.) DELIVERED TO YOUR DOOR, lcwt of
* WE HAVE STOCKS OF ALL DEVICES FOR WIDE RANGE WOBBULATOR. 5MHz to Electronic Scrap chassis. boards.
IMMEDIATE DELIVERY. 150MHz up to 15MHz sweep width. Only etc No rubbish. FOR ONLY U.
* WE CAN SUPPLY ANY FERRANTI DEVICE TO 3 controls. preset RF level, sweep width
ORDER. Send S.A.E. for quotation. and frequency. Ideal for 10.7 or TV IF MODERN TELEPHONES. Type 706. Two -
* WE ARE SPECIALISTS IN FERRANTI SEMICON- alignment, filters, receivers. Can be used tone grey, [3.75 each. Two-tone green
DUCTORS, WITH A STAFF OF EXPERIENCED with any general purpose scope. Full 03.75 each. Bleck 13.75 each, P. 8 P. 35p
ENGINEERS. instructions supplied. Connect 6.3V
Siemens BScBO246 SCR EI25 a.c. end use within minutes of receiving. Ideal EXTENSION TELEPHONES with
Complete kit of semiconductors L565 standard GPO type dial, bell and lead
SCORPIO Mk. II (State 6V or 12V when ordering)
All this for ONLY 01.75, P. 8 P. 25p. (Not
cased, not calibrated.) coding. 01.75 each. P. 8 P*. 35P.
BFS59 189 ZTX 304 29p ZTX504 55p ZSI70 I4p 2011: to 200kHz WB, SINE and SQUARE HANDSETS. Complete with 2 Inserts and
BFS60 21p ZTX3 1 0 12p ZTX5 I 0 25p Z5I71 16p
GENERATOR. Four ranges. Independent lead. 75p each. P. & P. 37p.
BFS6 I 21p ZTX3 I I 14p ZTX530 .29p ZSI 72 22p
ZTX312 14p ZTX53 I 34p ZS174 26p amplitude controls, therm Icor stabilised. DIALS. ONLY 75p each, P. 8 P. 25p.
BFS96 19p
23p ZTX313 16p ZTX550 25p ZSI76 33p Ready to use. 9V supply required. CS 45
BFS97 HIGH VALUE-PRINTED BOARD PACK.
BFS98 23p ZTX314 17p ZTX551 27p ZSI78 Sap each. P. 8 P. 25p. (Not cased, not call-
15p breed.) Hundreds of components. transistors.
ZTX 107 12p ZTX330 2Ip 2N3055 76p ZS270 etc.-No 2 boards the same. No short
ZTX 108 9p ZTX33 I 239 ZS27 I 22p
GRATICULES 12cm a 14cm high quality leaded transistor computer boards
ZTX 109 I4p ZTX382 15p DIODES ZS272 25p
29p plastic 15p each, P. 8 P. Sp. 01.75, post paid.
ZTX212 14p ZTX383 19p ZSI 20 15p ZS274
ZTX213 15p ZTX3B4 239 Z5I21 16p ZS276 389 BEEHIVE TRIMMER 3/30 pF. Brand new
ZTX214 19p ZTX450 23p ZS122 19p Z5278 6Ip Large quantity of good quality com- Oty 1-9 13p each. P. 8 P. 15p: 10-9910p
ZTX239 16p ZTX451 25p ZSI 23 Up ponents-NO PASSING TRADE-so each, P.8 P. 25p, 100-999 7p each, P.8 P.
ZTX300 16p ZTX500 16p ZS I 24 29p ZENERS we offer 31b of ELECTRONIC free.
ZTX30 I 17p ZTX501 17p ZSI 40 16p KS030A to GOODIES for 01.50. Post paid.
ZTX302 23p ZTX502 23p ZSI41 40p KSI 80A 18p HE CRYSTAL DRIVE UNIT. 19In rack
ZTX 303 lip ZTX503 113p ZSI42 39p BZVI9 series
15p
mount. Standard 240V Input with superb
ROTARY SWITCH PACK -6 brand new crystal oven by Labgear (no crystals) E5
MOTOROLA 130699 f1.10, B0700 MJE2955 [1.30, MJE3055 75p. switches (1 Ceramic; 1 off 4 pole, 2 way, each. Carr. C2.
RCA PRICES SLASHED, CA30900 stereo decoder C3.25 each. etc.), 50p, P. 8 P. 20p.
ZN414 THE FAMOUS FERRANTI RADIO I.C. ONLY f1.32 with data. 1,000pF FEED THRU CAPACITORS. Only
ORION. High quality printed circuit E2.55. Set of semiconductors 0e.95. P.C.B. PACKS. S 8 D. Quantity 2 sq. ft- sold in packs of 10. 30p, P. 8 P. 10p.
SIGNETICS. UA7411CV operational amplifier 5517 - no tiny pieces: 50p, P. 8 P. 24.
SEMICONDUCTOR KITS FOR GEMINI AMPLIFIER AND PW DERBY HEADPHONE ALWAYS SOME CHEAP SCOPES AVAIL -
AMPLIFIER AVAILABLE. Send S A E. for details. CAPACITOR PACK -50 brand new com- ABLE-or build your own. Send for our
ponents. only 50p, P. 8. P. 20p. tube list with a S.A.E.
pricean: list giving data and connection

X01
FREE! rCiiuerg i'l3rrnnsp;r rHoge of Ferranti semiconductors
- Just send a S.A.E.Copy sent with every order. PLEASE ADD V.A.T AT 8%
POSTAGE & PACKING 10p. FREE ON ORDERS OVER L3 OPEN 9 a m to 630 p m ANY DAY
ALL OUR PRICES INCLUDE V.A.T.
DAVI AN ELECTRON ICS CINILTINIZAMI LTD Mill=li BARCLAYCARD

P.O. BOX 38, OLDHAM, LANCS. OL2 6XJ rK 41,..., hen 7.9 ARTHUR ROAD, READING, BERKS. &'------ J -
Rear Tech Collegel Tel Reading 582605.65916

ETI TOP PROJECTS

100 -PAGE SPECIAL ISSUE
OF THE MORE POPULAR
PROJECTS FROM ETI

OFFERS: 100W GUITAR AMP

FIFTEEN BC108 ISSUE TRANSISTOR IGNITION
8 -CHANNEL MIXER
TRANSISTORS
UHF TV PREAMP
36 ELECTROLYTIC WIDE RANGE VOLTMETER
CAPACITORS £250 METAL LOCATOR
PHOTOGRAPHIC TIMER
PROJECTS: SOUND OPERATED FLASH
GRAPHIC EQUALISER TOP BURGLAR ALARM SYSTEMS
RUMBLE FILTER SIMPLE LOUDHAILER
PLUS: EASY PCB METHOD
SPECIAL SURVEY PROJECTS MIXER PREAMPLIFIER
FET DC VOLTMETER
OF CONSTRUCTIONAL KITS
BRAKE LIGHT INDICATOR
MATRIX TV FEATURE AUDIO ATTENUATOR
PLUS MANY MORE
AND MORE IN
REPRINTS OF OV. 200F THE MOST POPULAR CONSTRUCTIONAL ARTICLES
1000 GUITAR AMP
MIXER PREAMPLIFIER
El CHANNEL MAST. MIK.
LOWER PONER LASER

JANUARY'S ETI PROTOGRAPNIC TINIER ELECTRIC IGNITION

75p
METAL LOCATOR UNE TV PREAMPLIFIER

OUT NOW - 25p BURGLAR ALARMS

SOVNO OPERATED FLASH
NIDE RANDS VOLTMETER
SIMILE LOUDSPEAKER
OUT NOW-
TRANS, iTOR TEST.
AT YOUR NEWSAGENT
AUDIO ATTENUATOR
pLUS MANY MORE AT YOUR NEWSAGENT
k-) Practical Electronics January 1975
 CUSTOM CABINETS
331 High Street, Rochester, Kent. Tel: Medway (0634) 404199

KIT FORM REPRESENT HUGE SAVINGS

SPEAKER CABINETS IN

2' x 12" Cabinet 4' x 12" Cabinet Disco Console (includes lid not shown)
Takes two slaves

For a long time now a large number of customers have asked us to produce cabinets in kit form, and above we show
examples of cabinet styles and these are now available either fully built or in kit form ready for you to produce
a professional finish in a very short time !
Kits are available in all specifications and all the kits contain everything you need as follows :-
1) 4 sides with handle cutouts, front edges rounded, 1 back with jack socket hole, and1 baffleboard with speaker cutout
2) P.V.C. cut to size for frame and back, plus false front and back timbers, white front piping and speaker cloth
3) Recessed handles with fixing screws, jack socket, all fixing screws, corner plates, glue, and full instructions I
PRICE &TYPE LIST
Type Size Price manufactured Kit price
2 x 12" (illustrated above) 36"x 18"x 13"xl £21.45 £13.75
4 x 12" (illustrated above) 31"x 31"x13"xi £26.95 £19.25
4 x 12" P.A. Column 48"x 27"x13"xl £33.00 £23.65
1 x18" 31" x 31" x 13" x £26.95 £19.25
1 x 15" with two top horn cutouts 36"x 20"x13"xl £23.10 £14.85
Mini Disco (state deck cutout BSR, GARRARD etc.) 33"x 20"x 8"xl £22.00 £14.30
Maxi Disco (illustrated) (state deck cutout BSR, GARRARD etc.) 42"x 20"x10 'xi £27.50 £19.25
Please ask for quotation on any other type or size of cabinet you may require.

a a

ERC 100w power amplifier

* Stereo studio disco mixer * Electrolytic capacitors and second
* 100w RMS slave amp for Disco Full PFL and Monitor facilities generation ICs
* 100w RMS continuous sine wave * Fully protected against short or open
* As used by John Peel, Mark Wesley, circuit
output
* Short and open circuit protection Paul Burnett, DLT, Dave Christian, * Less than 0.1% distortion at all powers
* Built to highest industrial spec. Tony Prince * Rise time 4m uS-stability-
* Price £37.00 complete * Price £120.00 Unconditional Price £66.50

ALL OUR PRICES INCLUDE VAT AND UK DELIVERY

Disco imp projector 150 watt tungsten

unbeatable price
Includes liquid wheel and postage
Normally sold between £24-£2750

UNBEATABLE NOW ONLY £18

TRADE AND EXPORT ENQUIRIES WELCOME

Practical Electronics January 1975
 SYNTHESISER
Modules by Dewtron
(flust)
ELECTRON ICS
92 Warwick Road, Ealing, London W5 5PT
Telephone: 01-567 0424

HE 100 The synthesiser illustrated was built using Dewtron

modules, as sold to constructors for some years now.
100 WATT POWER AMP With over 10 years' experience in mail-order, we have
supplied many famous people and groups. Over 30 types
modules, some of extremely precision
MODULE of synthesis
design, e.g. VCO-2 log -law oscillator; 3 -wave o/ps;
sample/hold/envelope module; pitch -to -voltage
module allowing a whole equipment to "play itself" in
unison/harmony with any solo input or voice. Modules for
sequencer construction, too. Famous "Modumatrix"
patching system makes other patching a thing of the past!
Send just 15p for full catalogue to:

D.E.W. LTD.
254 Ringwood Road, Ferndown
Dorset BH22 9AR

Includes large black anodised heatsink-no

further heatsinks required.
Top grade glass -fibre P.C.B.
Uses high quality components.
Fully protected-short/open circuit proof.
Dimmit
Only 5 external connections. range of light
Fully guaranteed.
dimmers and lighting
control systems
TECHNICAL SPECIFICATIONS
Power output 106W R.M.S. into 811 Illustrated is the popular
PMSD1000 module. A 1000W
Distortion 0.8% at full 0/P. Typ. 0.4% professional quality dimmer,
linear operation, interference
Frequency response 15 Hz-23kHz suppressed. 60mm slider range,
Signal to noise Better than-96dB size 12 x 5 x 4cm. Ideal for low cost
stage and disco lighting. Used by
Input sensitivity OdB (0.775V) schools, theatres, studio. etc. Complete
with scale plate. fixing screws and full
Input impedance 10kfl instructions. C725 inc. VAT and P. & P.
Supply volts 45-0-45V Illustrated is the DD61 dimmer system.
Contains: six 1000W slider dimmers type PD1000,
six outlet sockets, a master control and a mains on/
off switch. Size 59 x 22 x 12cm. A complete system
in one unit for stage or disco lighting, etc. Other systems
Price £15.12 inc. VAT. (ready built) available with 1000W or 2000W dimmers with 2 -preset
and master controls.
OR The Dimmit range includes standard wall mounting models for
Complete kit (including P.C.B. and all components) home and office, etc. Professional modules for industrial heating
Rotaryy2410V slider control versions. Ratings: 1000W,
Iggiat3i3074et1^.0vRoa
£11.88 inc. VAT. Enclose 50p postage & packing. -1
Model SL800 sound to light converter. Modulates the light in time
Power supply for HE 100 (including transformer, with sound. Built in microphone. Just place unit near any sound source
capacitors, rectifier) £8.95 inc. VAT. Postage & -radio, hi-fi, TV, human voice, etc. No connections to speaker required,
simple wiring-similar to dimmer. Rating 800W. Complete with
packing 85p. full instructions.
For full information on all modules and lighting control systems
send 15p for our illustrated catalogue and price list. Personal callers
Pre -amps etc., also available. welcome, visit our showroom for a demonstration of any of the
modules or systems.
SAE for details.
YOUNG ELECTRONICS LTD.
184 Royal College Street, London NW1 9NN. Tel. 01-267 0201
CALLERS WELCOME

46 Practical Electronics January 1975

 Now onn-our new componnts shop. These pram arm very much lrgr sad will enable us
to have greater stocks than wa already have. Having all the components undo' one roof will now

C I T. ELECTRONICS guarantee you spent./ service on me counter, and on ins mall order side. We have n norm..
range of to chop from. If you e having problems to your components then
corn Iong. We re open from 9.30 a.m. through till 6.0 p.m. Monny to Saturday. Tin n ***** t

'
underground Chiswick Park, one there are no parking rostrIctIons.

NOW AT 267 & 270 ACTON LANE, LONDON W4 5DG

SEMICONDUCTORS S.C.R. ..SPECIAL 0 *
CR81/05 op TRIACS MINIATURE MAINS ****** ORMER.PRi
AC107 3Sp 8C530 40p MJ340 SSp Oft 65p 71041C 95P 202846 2150 CRS1/10 Sip TXL22813 8A 400V ggp 2405. SEC 120 100MA Manut . Hinchley
AC125 Sp BCY3 55p MJ481 950 0C42 40p 7IP42C 21.10 202904 25p ,.... ,,,, ize, 30 4 45 o 40mrn F C 53min
AC126 MJ2801 28 25 CRS1/20 60p SC/OD Price 1.415p. i00-np ea. 1.000-51/0 tie.
2Sp BCY32 93p 0C44 209 71650 OP
AC127 27p BCY33 aSp AAJ2901 E220 0C45 20p ZTX107 15p
202905
2192096
250
2Sp
CRS1/40 60 SC40E 21 .65 10.00040p eo.
AC128 28p BCY34 lip MJE340 OCT° ITX300 CRS1/60 90p SC45D "'TO ]CORE PVC INSULATED MAIM{ CABLE.
AC176
ACY17
27p BC538 15p MJE370
Sap
750 0071
15p
17p ITX500
150
1110
2192907
202926
2Sp
12p CRS3/10 .... Up SC45E U 10
2242
GREY ML8850 3 7.0 2rnrn Pace 100.
MN. 1000m -E35. 10.000m -E338'
25p 5C539 21.00 MJE371 Inp 0072 20p ZTX501 SOP 203053 250 CRS3/20 62p SC500
ACY18 300 BCY55 MOO MJE520 65p 0075 25p ZTX504 CRS3/40 110p SC50E £2.70 1.4701fd. NV MYLAR FILM CAPACITOR
SOp 2513054 05p Size In . 0.351n . 065in P C Mount
ACY19 30p EIC570 22p MJE295521.115 0078 259 210531 3.0 655 CRS7/400 21.00 DIAC 2Sp
ACY20 BCY7, 4163055 35p
203055 Price 100-n ea. 1000-3p ea.
25p 22p 0077 40p 27X550 250 203232 7Ip CRS16/100 Up
ACY21 30p 80572 25p MM1613 13p 0081 25p 0659 tip 2943525 115p
SW. A.C. SOLENOID. Reversible opera-
ACY39 55p BD121 7Sp MM1712 lOp 0083 25p N914
CRS16/200 90p hon. twin coil. Size appro. 2f . If . 18n
Op 203702
AD140 600 MPF102 45p 0034 1411 CRS18/600 21.60 811p ea.
BD123 ?Sp 25p N916 IP 203703 12p 30 unmarked 0071 translators [100
A0142 65p BD124 lip MPFIO3 0C139 30p 01001 SP 203704 120
C10813
C1060
:SP... LINEAR I.C.s 25 UNMARKED 250MW Zenedode. 4 75
A0149 850 BE/131 ?Sp (21954571 35p 0C170 25p 0I002 203705 Ann. "'" LM309K 5V. IA. VOlt- 5.15. 8,25. 7 5. 9 15. 105 Meaaured and
AD161
40162
40p
40p
BD132
80553
?Sp
np
MPF104
(2054581 35p
0C171
0C200
30p
SOp
04003
N4004
OP
90
100
2N3706
203707
12p
12p
12p
---
TIC44
110p

359
age Reg
LM723C 2-37V. 150mA
£2.10 tested.
Please state voltage required.
SO GE Diode OW eguivelent
[1 .00
51 00
AF714 2Sp 80156 ?Sp MPF105 0C201 60p 04005 120 203708 2N4444 21.9
125. Voltage Reg. 2 05
AF115 25p BDY11 t1.40 (205459) 400 01202 7Sp N4006 150 203709 12p 8110/5004
.

1.-- ...... ORMER: DOUGLAS PRi. 0. 115

AF116 25p 1313Y17 8110 1APSA06 360 TIP29A 007 180
Wi0 MFC4000 250mW Audio Op 200 220. 240 SEC 25-0-25-0-8V. 2fA. [4 -SO
203771 22711
AF117 2Sp BDY19 2805 MPSA16 313p 71030A Sisip 194148 711 203772 1.275 BRIDGE RECTIFIERS TBA800 5 Waft Audio t150 . Olp.p
AF118 600 8E152 Sip MPSA56 35p TIP31A up 20696 250 203773 22.05 W02 IA 200V Up 7091 Op Amp D.I.L. TRANSFORMER
AF172 30p 13E194 14p MPSU06 ?Sp TIP32A 74p 20697 220 203819 1099 asp PRI 0.115. leo. 205. 225. 245. SEC 35-0-3
7IP33A MOS
3513 851134 14A 200V 57p .

1-2A 81.511 - Ilep. p.p.

ASY2f1 30p 8E195 15p MPSU56 7110 251698 250 203820 55p 741C Op Amp 814
ASZ21 60p I3FX29 30p NKT135 350 TIP34A MSS 20706 12p mum up MDA952/2
6A 100V Up 0.1.L. 7099 .. 55p MU ..... TUBULAR CERAMIC UHF
BA102 33p BFX8.4 30p NKT222 259 TIP35A 63.31 207060 203904 TTylil..1M.MrS IPRoOarn5,107510
lip 150 22p 748C Op Amp D.I.L. 75p
BA112 50p EIFX85 30p NKT401 T1P36A 22.115 20708 150 203905 25p USER DIODES
66114 16p EIFX86 30p NK1404 110p TIP41A 755, 20930 20p
757C Dual Op Amp 21.20 0.8-2 2p .. Price 100 e
801
204058 12p MTN S/1005 40051W 214414 Radio I C 6125 0.5.1.30
991
BA156 15p Mom 20p NKT773 30, Tip42A pap 201132 25P 204059 12p 3 30-33V. 5% .. 11p
BC107 1.1p 13Fyio 35p NKT774 2Sp TIP29B 58p 2N1302
.
TAD100 Radio I C int QUANTITY DISCOUNTS PLEASE TELE-
1811 219/060 120 I5W range [1.90 PHONE
BC108 14p BEY44 513, °Al° 20p TIP21 lop 2N1303 15p Nagai 12p .. 25p Filter
9C109 150 SF550 29p 0A47 Op 1(9218 70p 201304 25P 204126 17p 10W r" 98 - - 45P CA3014 81.55 woopF Fenthrough capacitor
Miniature tubular P.0 trimmer*
zp
BC147 12p BE551 2Sp 0670 12p 711/32B 220 201305 25p 204286 15p 063018 ti .0e
Ilp 3 5-13pF
BC148 129 63F552 2Sp 0079 TIP3321 21.12 201306 25P 204287 13p T1L2122
20 CA3028 21.20 6.300F ' lap tilt.
BC149 12p 6E953 25p 0081 10p 893413 Mlle 201307 250 204288 15p 28, CA3038 (1.00 ap c.o Parley roon relay SOP .40
Np 0090 HP5082
BC153
8C157
15p 8E590 10p TIP35B 22.01 2N13013 2512 2194289 15p
MA2082R
sp CA3046 5561 TO3 VOLTAGE REGULATORS
140 55w63 55p 0491 10p T1P368 23914 201309 25P 20/290 15p
BC158 15p EISW613 04200 10p 719418 en 2N1613 25p
CA3048 2215 L005 5V 8513rnA
BC159 8SY95A
1100
04202
204444 11110 L.D.R. CA3075 map L036 125 500mA
150 12p 10p 1194213 98p 201711 25p 204071 350 L037 155 450mA El ,S0 00,
BC169C 141, C111 Sep 06210 35p TIP29C 710 202147 ORP12 UP CA30900 2445
700 204920
.

BC182 14p C426 40p 0/4211 36p 71030C In 202160 550 205191
11013
Ni p
NE555 Timer 99p MC1303L 62'20 VEROBOARD
13C183 14p 85100 1Sp ()CU 90p TIP31C 115p 202217 25p 205194 61-10 METAL BOXES . a i 0 15
BC184 14p 135126 20p 0C19 85p 71032C 21 -OS 202218 25p 20 .. 34 23p
ALUMINIUM BOXES IDEAL FOR VEROBOARD WITH BASE
1.-- High 50p400
10360 5012 5
BC212 1Ip B1(127 20p 0C22 lip 71033C 8830 202219 25p sow 50p AND P.S. SCREWS 34
34 / 34
33p 5p

35p
3Sp
350
BC213 1Ip 195164 Op 0C26 116p TIP34C 21.90 2N2222 200 40362 55p A87 20- Long 51." Wide 41p
BC214 14p 15100 15p 0C28 115p T1P35C 23211 2192222A 25p 4.1513 MO 17 - 21 8105 79p
BC238 12p 15103 20p 0C30 NP TIP36C 24.10 202398 (0p 0219 21' HP' 17 . 3f lit -0 E1 .12
BC239 AB1 SIM
12p
-
5
202646 Sep
A13,0 1
ABi2 2- 1
allp
Pep
17 .
PIN INS TOOL
SP F CUTTER
5
" 71:i
52p
20
5 2p
DIGITAL INTEGRAL CIRCUITS
10-3
A1513 2 70p
5/47400 20p SP47428 50p 007473 441p
SW 107
SN7 110
20p
lOp
5074166
SN74167
64.06
05.25
A2114
0815 a-
ti..
1140
100 PINS SS
100 PINS DS
500 PINS SS
nn
68 20
30p
01 2o
ni1
no
507401
.,, "42
.

220 SN7430 200 S07474 40p SN7 118 61-00 01474170 81.10 3- ti 20 01 20
.4816 2109 500 PINS DS
SN7402 20p 007432 42p SN7 119 21.00 5074171 62.00 'pi. Prices Correct June 12
El . 20
507403
007404
20p
20p
S07433
007437-
7110 507476 Op SN7 121 lip 0074175 6835 A139
12-
12"
3
[1E0 STOR DATA BOOK/
050 SI47480 500 SN7 122 21-35 St4741713 01110 ALUMINIUM BOXES WITH SLOPING TOP -IDEAL NEW SERIES
607405 200 SI47438 lip S07481 21.25 SN7 123 22.70 SN74177 2180 FOR PlIE-AMP11. ETC., USING SLIDER CONTROLS 1 DTA3 USA Band 3 Trensito. Chan/ -
SN7408 30p S07440 011p SN74412 11711 $07 141 S1974180 61-55 A1320 8" Long 9 Wide 3f High at back . wince. 21421-2N6269 all numbers
S07407 300 SN7441AN 75p SN7483 21 00 5147 145 11-50 High ail front 6' Slope to front'2- " 2. THT Thyristor. Trin. Mac. Put. UJT
507108 SN7442 007484 00p
SN7/181 67.00 2
With P K Screws 3 0715 Japan. Transir
2S0 Chars,
"'"
2013 5147 150 23.3S SN741112 62.00 teriatics. 2SA. 2S13. 2SC. numbers
5447409 45p 5047443 61.00 0947486 450 SN7 151 21.10 SN74184 62.45 AB21 As ebove but 10" long 4. OVT Diode. Comparison Tables.
0147410 20p 507445 62-00 SN7490 ?SP SN7 163 61.35 SN71185A 62.40
A1322 As above but 12- long 52.40 5 Band i. Trans:nor Characteristics
007411 23p SN7446 5280 SN7491AN 21-00 SN7 151 E2-00 SN74190 2195 V41 VU noSe European nunnen AC AF. BC. BF etc
SN7412 41p SN7447 Et .75 SN7492 75p SP47 155 El - 56 99471191 81-95 The vo is calibre,. -20 lo - 3 and 0-100% rn....lont.:rt fi Tr ,0T0r:inacistor ,Enopu,invacmonninT.:12,Le:..12
507113 30p S147418 Et - 75 0617493 ?Sp SN7 156 28 55
SN7416 30p S07450 Sip S07194 spill 157 ti.ag S1974192
sN74193
22-00
22.00
tnr:141.,c-:, nn.°°"°°° 1.0017°°°° on .° :4orniconL:n'r.outlines
SN7417 SO SN7451 SOp 00749S top SN7 160 62.60 iiiinisitiviry't '130 A. M resistance: 600 ohms I PRICE. 81-10 per book. LI per 8 boon inc
11 SN74194 2.2 50 Otatensionst 40 40 0 rarnm
SN7420 30p SN7453 SOp SN2425 21.00 SN7 161 2280 SN71195 21.05
SN7422 411p 507454 20p 007497 [1.2S 507 162 2300 S074196 21 -SO ALSO STOCKED THE LARGEST RANGE IN LONDON
SN7423 ilp 007460 20p SN74100 22.50 SN7 163 23-40 SN74197 81.SO Electrolytic Cepacitors Mullard. Sprague. Lorlin. etc Unlem other.u leafed all price are
507125 MO SN7/70 Sip SN74104 E1.45 SN7 164 t2-75 SN74198 81110 n Silver Mica Capacitors. etc EXCLUSIVE or V A 7 Memadd 8%
SN7427 420 SN7472 30p SN811.05 21.40 SP174165 81-00 SN74190 [4.110
2:Z= ZY0°IirPon.ientiornaters. carbon. whew and to all orders Crrmle. bIdeIbnde,
Preset, multiturn. Antes Soldering Irons
Rectilinear ES - 200 Over 05 potit fros
QUANTITY DISCOUNTS -12+ 10%. 25+ 15%, 100/ 20%. switches. rotery. slide. toggle. etc Cable. veroboard

AUDIO ACCESSORY SHOP, 17 TURNHAM GREEN TERRACE, CHISWICK, W.4

MICROPHONES TWEETERS CASSETTES
PRICES INC VAT PRICES INC VAT PRICES INC VAT
C75 Cons Twos's' Frog 3000-15000Hz Cron- C60 C90 C120
CM10 Crystal Lapel Microphone with Lead and over frog 3000Hz Imp 8 ohms Suitable for BASF LH NP £1.21 8171
Plug ISp *Warn up 10 10 watts RMS ... 81.98 . . MEMOREX
CM20 General purpose Crystal Microphone El 20 CT188 Pressure Unit Np
CM73 Crystal Stick Microphone with Switch
Load end Plug E2 20
1500-16000Hz
Type Tweeter
Croon.' fret
Imp 8 ohms Suitable for system. up to 20
Flag
3000Hz
MROX2 Oxide
CR0X2
PHILIPS
2847
15p
[1.32
21.1/1
21.10
-
El ?I
El 7S
C092 Omni Directional Capacitor Microphone watts RMS Mee OTT Onounts 12-10%. 24-15% 36-20% 60-25%
with built.in Preamplifier. Cable and Wind- CT10.16 As /bowl but 16 ohms .. 2200 SPEAKER CLOTH
shield 014 00 0133 Dome Tweeter Frog 2000-18000Hz CrOlia- Available in Bleck or Green, Approx width 81in
C096 Cardloid Capacitor Microphone as sbove. over frog 3000Hz Imp 8 ohms Suitable for 81,75 d.
both type. with Switch both 600 ohms Eli 00 systems up to 10 watts . 25.70 HEADPHONES
DD1 Casette Dynamic Microphone with Plugs FF27 Dome Tweeter Frog 2000-20000Hz Cross- Type 0-202 Entine Mono/Verso *witch. Volume
for Ignel and stopstarl 200 ohms E2 20 over frog 300002 imp 8 ohm. Suitable for Controls on each channel Frog ...pone 20-20.000Hz
DOS Elect's! Paging Microphone. on table Hand systems up to 30 watts RMS . . E2 -SO Impedance 4-16 ohm. [4 -MI.
with gooseneck and switch 600 ohms 214 00 FF28 Horn Tweeter Frog 3000-20000Hz Cron- TEAK VENEERED SPEAKER CABINETS
DD6 Lavafter Microphone with Windshield. oiter frog 300002 Imp 8 ohms Sultsble for For 8 5In Speaker Size 91' 13r . S1 0.50
Levan, Cord. 6 metros Cable 600 ohms sylftetn up to 20 watts RIPS .. 21-20 Bin - Topple' 74.116.5i [EN
50611 511.20 H715 Horn Twain, Frog 2000-18000Hz Cross. 13 .13in 104. 17.6 45.75
01.418HL Dual Impedance Dynsmic Microphone over frog 3000Hz Imp 16 ohms Suitable for 13 . 8in Tweeter 12. 181' 54 [1 SO
with desk stand 600 ohmcsokn 81050 rystems up to 30 watts RMS Cl 00 12in - Tweeter 15f . 4.84 [KM
DM73 Omni Directional Dynamic Microphone HT21 Horn Tweeter Frog 2500-20000Hz Cron- VALVE AMPLIFIERS
with desk stand 6 metres Cable and Plug. over leg 3000Hz Imp 8 ohms Suitable for PRICES INC VAT
50k() 810110 systoms up to 40 watts OHS Cl 20
DWI Remote Dynamic Microphone. Cassette MH710 Horn Tweeter
Robust units suitable for moat PPDco nos
Frog 2000-18000Hz watt inputs. Vol. Treble. Bass Controls 81250
type with Plugs 200 ohm. [1.50 Cronover frog 3000142 Imp 8 ohms SiU
5 2

DM82 Remote Canon Cardioid Microphone 15 watt 4 inputs. Vol. Treble. Bass Controls 2.24111
Ole for interns up to 30 watt. RMS £4-00 30 watt 4 inputs. Vol. Treble. Bass Controls 221 .80
with Plugs 200 ohms 62-40
DM94 Omni Directional Dynamic Microphone 50 watt 4 inputs. Vol. Treble. Ban Controls 2311.25
with Slide on Windshield and Switch 50611 Cl 50 150 weft 4 inputs with separate vol controls
DM614 Pencil Type Dynamic Microphone with plus "nester vol treblo. bag . E7500
Cable Liman' Cord and Base SOW 03 20 CROSSOVERS 500 weft 4 Inputs each with independent vol.
PROMS Lanlier Capacitor Microphone with Tie PRICES INC VAT trble and bass control plus over11 male'
Clip 513 mem, Cable 600 ohms (IV 00 CN23 2 Way Cronover Network Imp 3 ohms vol control 2124 S0-
PRO6110 Omni Dinctional Capacitor Micro- Crossover 300002 Suitable up to 15 watts MICROPHONE MIXERS
phone with 6 metre. Coble 600 ohms 030 00 WAS 21.70 PRICES INC VAT
PROM20 Lint -Directional Capscilor Microphone FFS 3 Way Crossover Notwork Imp I ohm. FF1 4 Channel Mono Mnar and P.sarriplifier
wIth 6 metres Cable 600 ohm. E32011 Crossover frogs 1000 and 5000Hz Suitable with indtvidual slide control. Battery
PROM25 Capacitor Boom Arm Microphone with up to 25 watts RIPS .. 23.30 operated . 250 MI
Arm. two Windshields. Coble 600 ohms 63100 FF30 3 Way Crowns' Network Imp 8 ohms FF10 7 Channel Slew Min, and Preamplifier
UD5OHL Cardloid Dual impedance Microphone Crosson' frogs 1000 and 5000Hz Suitable with individual slid. controls Battery
with Switch. 6 mtre Cable and Plug 600 up to 25 watts RMS 0.20 °pentad .
234.00
ohms 50661 [12.00 SN75 2 Way Crossover Network Imp 8 ohms. FF11 Stereo Frequency Controller and Pm -
2000 Stirs Line Crystal Microphone with Switch Crossover 300001 Suitable for system. up amplifier. use. five slide controls Battery
Cable and Connector 23.10 to 15 intts RMS 04.60 operated 234 00 .

All mail order and enquiries to 270 Acton Lane Tel. 01-994 6275
Practical Electronics January 1975 87
"SLO-SYN" 3 -LEAD Ultra PRECISION SILVANIA
MAGNETIC SWITCH
CENTRIFUGAL BLOWER
SYNCHRONOUS STEPPING
MOTORby
Type SSI5 These ,
Air Control Ltd.
30 segments individually bsinced
heavy cost alloy case 2.300 r p m 240 V
in
Now complete with reference magnet'

A magnetically activated switch. vacuum sealed

in a glaze envelops Silver contacts, normally

' ftirf(TC
fine motors are a c Very powerful and silent running closed Rated 3amp at 120v. lIarrip at 240v
easily reversed . 5I'' die 3' Inlet die Outlet 31 2}" Size (approx i 1,4' long x i'' di Ideal tor

I
burglar alarms. security systems etc end
I ii: starting and Limited number only 68.95. P. 8, P.
.

stop -
..., ping in less than 5°
-----..._._
.
wherever non -mechanical switching is required
11 -- 40p 10 for t210: P 8 P 15p 50 for ta; 100 for t15.50.
without electrical
--\..... ../ or mechanical FREE P 8 P over 10
...- braking Simple MAINS
relay circuit can
be applied to give DC to winding for a maximum SOLENOID
holding torque of 300oz in with 35v at 0 35 amps This little unit gives AMPEX 7-5V. D.C. MOTOR
through winding For AC (synchronous) operation at vertical lift of approxi-
50Hz Speed 60 rpm at 60Hz 72 rpm STEPPING matey 1' through hinged .1..
120r
Holding torque et 50 steps per second -100 oziin Can
be wired to give 100 or 200 sip. per revolution with
elbow Bracket into,
11

Length of arm 2f 240V AC

- _
An ultra precision tape motor
porates 2 fixing screws f'" designed for use in the AG20
accuracy of 0 1° per step non -cumulative Torque Pull at coil is approximately 1lb El. FREE P 8 P
characteristics can be modified by simple R C circuits portable recorder Torque
Special quotes for quantities 450GAVCM Stall load at 500m
Dimensions die 4 body length 4f spindle length 1-,I1
.

Draws 60ms on run 130Orpm -

2j -t, die Weight 130 lbs BRAND NEW in makers .'

speed adjustment Internal AF RF

packing Offered at less than }makers price SOLENOIDS i-11..1' suppression }"die v 1 -spindle
OUR PRICE ONLY CIS
by WESTOOL motor 3" die v If" Original
cost E16.50. OUR PRICE t3.30.
NORPLEX 240AC type MM6 P 8 P 25p Quantities available
Fibre glass copper -clad laminate Finest quality epoxy
Ib pull. 1." 1-.....---. r-Mu -metal enclosure available
resin base Heat resistant. Ideal for P C e Size 12" v li' Travel 1' 90p.
- /4 ?Sp each. FREE P 8 P
12 24- ,2'.21' - 24-. FULL SHEET 43- 37. (11 sq ft each & P 10p
P
--

Single -sided Copper with thickness of W 3/64- W

;

240AC type MM4 2lb pull.

ii. v If x I Travel I.- 70p
Also double -sided ,I,' -,' ,4 Et per sq ft Cut sizes
1-10 sq ft 125p P 8t' Full Sheet Ell each Carr El for 1st each P 8P 10p Quantity
discounts 10-50 10°. 50 up -
sheet plus 25p each additional sheet wards 25.. ALL PRICES INCLUDE V.A.T.
SMITHS RINGER -TIMER
15 minute 'Imes spring wound
Whilst we welcome official
C77) Reliable OPEN FRAME
'''......10
(concurrent with time setting) 15 lrnin
divisions. approximately between f shaded pole ,
orders from established corn -
IOW divisions Panel mounting with chrome
bezel 31' die El .40. 15p P 8 P
GEARED MOTORS
7.
panies and Educational Depart -
(Dural gear case) 4%,,
240 ATORQUE.
26rpm NEW merits, it is no longer practical to
KNOWLE (U.S.A.) MINIATURE HIGH approx.
MICROPHONE CAPSULES overall size 35 e-
spindle idies as illustrated. E270. P 8 P 30p
Impedance approx 2000 output 60 or 80 DB at Kc
As used m deal side bugging device etc Size ISO DB)
1
21.
Similarto above. 19 pm [2-70. P 8 P 30p fore, remit cash with
please
Orpm with pressed steel gear case (similar to above but
Ti 7, , 001 0 ,,,,,
134)
tested £t 20 each P 8 P FREE
i E. equipment.all 11 SLIGHTLY SMALLER) t2 ?O. P 8t' 30p orders below this amount.
ELECTRO315/317, EDGWARE ROAD,

- TECH COMPONENTS LTD "

LONDON, W2.
Tel: 01-723 5667 01402 5580

SPECIAL OFFERS RECTIFIER ZENER

TRANSISTORS TIP41A
TIP42A
ZTX300
68p
lip
lipp
2N2905
202926R8
2N20260
16p
Bp
Sp
FETS
BF244
MPF102
30p
319
55p
28p
CAK46 55p
55p
DIODES
500mA
SIGNAL
DIODES DIODES
3 3V to 33V
ZTX304 24p 20 2926YG Sp MPF103 31p 245p SN7.:, 95p
BY100 15p BA100 10p
16p 8E041 2ap ZTX500 15p 2N3053 lop MPF104 31p 52p 400MW 9p
AC I26,'7 11p 0177 MC 220p 0A47 7p
AC128 tip C178 17p BFX29 309 ZTX504 50p 203055 409 MPF105 31p 1 Amp 1 3W llp
AC176 lip C179 16p BFX30 310 2N096 15p 2N3442 140p 203819 20p
OPTOELECTRONICS
81126 12p 0A70 8p 1 5W 25p
AC187 12p Cle2 lop SPIN 15p 2N697 13p 2N3702/3 ilp 2N3620 57p BY127 12p 0A79
ACI88 tip C163 10p BFY51 159 2N698 30p 203704/5 llp 2N3623 110p Photo- Light ' 7p 7W 40p
AD149 43p C164 lip BEY52 15p 214706 12p 2N3706/7 llp 2N5457 31p Transistors Dependent 154001 5p
0A81 7p
AD161 37p C212 lip BRY39 34p 2N708 lip 203706/9 Sp 205458 31p OCP70 50p Resistors 154004 Op
0A85 9p Other
AD162 37p C213 111p MJE2955 95p 20930 2N3772 1$1p 2N5459 31p OCP71 asp ORP12 50p 104007 7p Diodes
AF114/5 13p C214 13p NJE3055 $5p 201131/2 189 203773 2409 2N5777 50p ORM 55p 1.5 Amp 0A90 6p
TUNNEL
AF1113/7 13p 0115 55p OC213 40p 201302/3 17p 203903/4 lop MOSFETS 6p
201304/5 21p 204058 15p RLEedDsigTil,L20G9 1..11np 305RpPy13.11 PL4004 10p 0A91
AF139 41p D124 7 0C26 Sop 40603 AEY11 50p
AF239 44p D131 429 0C35 li 2N1306/7
201308/9
26p 204060
205191
13p
95p
40673
5119
110p
MINITRON 3015F 120p
3 Amp 0A95 7p
BC107/8 9p D132 4 0C38 52p 2Bp 40841 75p PL7004 20p 0A200 6p
BC109 10p F115 0C41/2 15p 201613 29p 205104 $5p 90p
VARICAP
22p5p
Zip
30128 LATEST ICs- 6 Amp
BC147/8 7p F167 23p 0C44/5 lip 201711 30140 asp MANY APPLICATIONS
OA202 7p BA145 17p
BCI49 F173 25p 0070/1/2 lip 2N2219 20, UJTS 750 BY210 31p 4p BA148 15p
OP
209 T1S43 rip 30141 ICL8038 Voltage Controlled 1N914
BC157 13p F184 22p 0073 SOp 2N2221 BYZ11 35p 15p
BC158 12p FI94 lip 0081/2 12p 2N2222 20p 2N2160 ?Op Oscillator 250p 10916 6p 1313103

FR39 21p 0083/4 by 202369 14p 202641 34p NE567 Tone Decoder 250p BYZ12 33p BB104 30p
BC159 14p 154148 4p
BC 169C 12p FR40 219 TIP2955 70p 202484 309 204871 31p (Application Date 10p) BYZ13 311p BB105 30p
TRIACe VOLTAGE REGULATOR
SCR-THYRISTORB 100V 400V 500V
BRIDGE RECTIFIERS 50V INV 400V 600V ML723 5Sp MFC4064 Op
lip 3 Amp 55p Illp 120p 1 Amp Plastic
250mA
50V
lip -tip
100V 400V 600V 1 Amp
3 Amp
42p

--
43p
48p
49p
60p
71p 100p
6 Amp
10 Amp
Sep
109p
120p
154p
150p
165p 7805 sv
1702201 17051
140p - (T03)
175p
1 Amp
2 Amp
4 Amp
29p
30p
47p
35p
41p
24p
45p
$0p
25p
48p
70p
7 Amp
16 Amp
80p
Itp
$4p
alp -
115p
16 Amp
Other
145p 110p 200p 7etz
ieri5
I2V
15V
140p
140p
140p
90p

-
90p
Other 40430 90p, 40488 115p, 40669 95p. 7818 115V
6 Amp 55p 60p 78p Up C108D 45p, 2N3525 91p, 204444 165p DIAC S12 for use with above trice 21p )824 24V 140p -.

LINEAR ICo ZN414 Radio receiver llOP 7 76 37p

CA3040 Transistor Array Sp NE539 FET OPA 21.92 TTL ICs 744t 75p C-MOS IC
CA3040 4 Independent Amps asp NE555 Timer 559 7400 14p 7442 70p 7 80 $5p CD4001AE Sip CD4018AE 360p
CA30139 FM. IF Amp 250p NE550 DuI 555 120p 7401 16p 7447 115p 7486 41p CO4009AE 120p CD40274E 170p
CA3090 FM Stereo Decoder seep NEMO PLL 2115p 7402 16p 7448 120p 7 89 340p Cf:/40114E 50p CD4029AE 420p
LM301 OPA with eat comp. Lep NE541 PLL with AM Demod 265p 7404 lip 7450 22p 7 90 52p CD4012AE 51p CD4037AE 2109
LM307 OPA with int. comp. SOp NES02 I'LL with VCO ease 7408 tip 7454 22p 7 92 tep CD4016AE 120p CD40474E 115p
MC1303 Stereo Pre -amp 190p NESS Precision PLL ease 7410 lip 7460 22p 7 93 55p
MC1307 FM Stereo Decoder 129p NESS Function Gen 299p 7413 Zip 7470 30p 7 107 45p
MCI310 Collette FM Stereo Dec 241p NE507 Tone Decoder 250p 7414 30p 7 121 34p
12p 7472 We supply complete eemicon-
MC1312 SO OuadrPhOni. Dec. Sap 7416 33p 7473 36p 74122 lip
NIFC4000 I Watt Audio Amp. sap Popular Op Amp. ductor parts Including sockets
MFC9040 Electronic Attenuator Hip ML709 OPA with .at. comp 2Sp 7420 lip 7474 Up 74123 1100 for various projects In P.E.,
MFC11070 Zero Voltage Switch 290p ML710 DIN comparator 35p 7430 lip 7475 SSp 74141 85p W.W.. P.W.. TELEVISION. etc.
TAA570 Limiter Amp 170p ML741 OPA with Int. comp 26p TELETENNIS
TBA570 Radio receiver 11109 ML747 Dual 741 75p TRICOLOUR LIGHT UNIT
190p MOS OPA with ext. comp ACCESSORIES DIL SOCKETS
TELSOO 5 Watt Audio Amp Sap
RHYTHM GENERATOR
713.41110 7 Watt Audio Amp 12fp 8 pin 12p, 14 pin 13p, 16 pin 14p. MINISONIC SYNTHESISER
TBA/120 2 Watt Audio Amp. lap TV ICe Prices on ePPliSitiOn
TCASO 10 Watt Audio Ampotter 320p Data sheets on above IC lip .arch. Mica bushes for 703 and TON Sp. TOS GAS DETECTOR

Minimum order £2
All prices exclusive of VAT.
All goods brand new and guaranteed to
manufacturers Specification TECHNOMATIC LTD.
P 8p 10p for orders under E5 Money refunded If not satisfied. 54 Sandhurst Road. London NW9

Practical Electronics January 1975

 Practical Electronics Classified Advertisements
RATES: 11p per word (minimum 12 words). Box No. 30p extra. Semi -Display £8.50 per single column inch. Advertisements must be
prepaid and addressed to Classified Advertisement Manager, "Practical Electronics" IPC MAGAZINES LTD., Fleetway House,
Farringdon Street, London EC4H 4AD

RECEIVERS AND COMPONENTS PRECISION POLYCARBONATE CAPACITORS

ALL HIGH STABILITY-EXTREMELY LOW LEAKAGE
TTL AT LOW PRICES!
(All devices ex -stock. Prices include VAT)
440V AC (±10%) 63V Range 1/24 25/99 1/24 25/99
0.1µF (le' X r) Sop , L20. ,5% 7400 0.17 0 -IS 7402 0.17 0 -IS
ALLARD ELECTRONICS 0 229F (111"X r) 599
0 25µF (11" X I') 62p
047µF 66D
1'0µF 66p
489 36p
Up 46p
7404
7420
0.20
0.17
0-18
0.15
7410 0.17 0.15
0 17 0 -IS
Branded Components-Full Specification 7430
0-47µF (11' X I') 71p 2.2µF SOp 65p 559 7440 0.17 0.15 7442 074 0.73
TRANSISTORS SCR's Price DIODES Prier 05µF (11' X 5') 75p 4'7µF 11.80 01.09 136p 7445 1.03 0-96 7447A N 0.98 0-98
Price ea. ea. ea. 0-68µF (V x5') 80p 58µF 11.64 11.29 11.09 7451 0.17 0 -IS 7473 0.36 0-34
AC125/6/7/8 0.15 CR81/05 040 1N914 0.05 1.0µF (2'Xf') 91p i0 OAF 0000 11.60 01.40 7474 0-36 0.34 7475 0.56 0-50
AD140/149 1200 CR81/10 0-66 1E4001/2/3/4 2.0µF (V x 21.22 15.0µF 12.79 6015 /140 7476 0-35 0.32 7480 0-53 0-50
AD161/162 047 CR81/20 COI) 7483 102 0.95 7489 3.56 3 33
AFI14 5/6/7 0.15 CR81/40 0.45 1N4005/6/7/8 TANTALUM BEAD CAPACITORS-Values available: 7490 0.57 055 7492 0.57 0.53
AF118 046 CR83/40 0.65 0-08 (1.1, 0.22, 047, 1.0, 2.2, 4.7, 11.8ia at 15V/25V or 35V; 7493 0.59 0.56 74121 037 0.35
BC107/8/9 049 CREI7/400 048 10.0µF at 16V/20V or 25V; 22-0µF at BV/10V or 16V; 74123 0.72 0 67 7486 036 0.34
BC147/8/9 0.10 CR816/100 046 FREE 33-0µF at 6V or 10V; 47-0p.F at 3V or 6V; 100.09F at 3V. 74157 0.87 0.81 74175 1.01 0.95
SC182/3/4 0-10 CRE116/200 048 INTRODUCTORY ALL at 10p each, 10 for 960, 50 for 04.
BC212/3/4 041 CRS16/600 140 OFFER All devices full spec. by famous manufacturers.
25 Metres
TRANSISTORS: BC183/183L lip BFY50
20p Devices may be mixed for 25/99 prices. S.A.E.
BCY70/71/720.16 BC107/8/9 99 BC184/194L 12p BFY51
20p for full list. 10p P. & P. on orders under Cl,
BDI31//32 046 TBA1400 1.38 Connecting Wire BC114 129 BC212/212L 14p BFY52
209
BF194/5/6 043 free data with every
every order BC147/8/9
otherwise post free.
109 BC547/558A 129 AF178
30p
BFY50/51/52/53 SPECIAL (5 X in BC153/7/8 12p BF194 0071 129 12p J. C. JONES
0413 OFFER various colours) BCI82/182L lip BF197 2E3055 139 50p 46 BURSTELLARS, ST. IVES
BYI27 0.25 ZN414
MJE370 0.62 RADIO I/C
POPULAR DIODES -1N914 Op, 8 for 46p, 18 for 90p; HUNTINGDON PEI7 4XX
MJE371 0.78 El Free circuit PULL RANGE 1E91639, 6 for 46p, 14 for 90p; 1844 59, 11 for 509,24 for (Mail Order only)
0C28 0.50 8N7400 series, 11; 1144148 69, 6 for 27p, 12 for 48p; 121400155p; 1E4002
OC35 Veroboard, Pots, Op, 1:44003 619; 1144004 7p; 1214005 71p; 1N4006 9p; "EX -EQUIPMENT COMPONENTS. Indicators
990 BZENER8 0.10 Caps, etc., etc. 1E4007 UP.
0083 Q20 ZY88 LOW PRICE ZENER DIODES-400mW, Tol. 15% at modifiable to aerial direction monitors,
TIL209 22 All voltages Send for Free List
2E2218 0.19 BZX61 series S.A.E. pleave bmA. Values available: 3V, 3.6V, 4.7V, 5.1V, 5.6V, chokes, relays, switches, instruments, fuse -
2N2906 0.13 1.3W 0.17 6.2V, 6-8V, 7-5V, 8.2V, 9.1V. 10V, IIV, I2V, 13V, holders, push buttons, caps.. etc. S.A.E. for
2N2926 all
13.5V, I5V, 16V, 18V, 20V, 22V, 24V, 27V, 30V. ALL at list. ELDUN ELECTRON 1( s. 10 Raven
0.11 BRIDGE RECTIFIERS 7p each, 6 for 89p 14 for 84p. SPECIAL OFFER: 100
2/43053 0.15 Price each Zeners for 116.60. Road, Timperley, rhrshir."
2143054 040 lA IA 4A 8A RESISTORS-High stability, low noise carbon film 5%
2/43055
2E3702/3/4 040
2E3705/6
044
0.10
50V 0.24 0.34
100V 0-24 0.39
0.64
-

0.54 0.69
5W at 40°C, OW at 70°C. Ell series only-from 2.20 to
2.2M0. ALL at 1p each, 8p for 10 of any one value, 70p BETA DEVICES
200V 0.27 0.44 0.58 0.79 for 100 of any one value. SPECIAL PACK: 10 of each FOR BETTER PRICES
2E3707/8/9 0.10 400V -
2N3819 0.211 600V 0.29 -
0.49 0.64
0-74 -
0.89 value 2-211 to 2-2M11 (730 resistors) 06.
SILICON PLASTIC RECTIFIERS-FS amp, brand new
wire ended D027: 100 PIS. 7p (4 for Sep); 400 P.I.V. 89
TRANSISTORS
AC187/188
PR.
I.C's DIODES & RECT.
709C TO.99 0-30 121914
040 7090 D.I.L. 0.80. 1N4148
0 04
299/301 BALLARDS LANE (4 for 309); 800 P.I.V. lip (4 for 42p). BC107/
0 04
LONDON N1213NP 741C T0,99 0.86 11Y127 0.14
MAIL ORDER ONLY Telephone enquiries: BRIDGE RECTIFIERS -25 amp: 200V 409; 350V 415p; BC108 0.09 741C D.I.L. 0-36 1144001/2 0-05
01-445 5188 Cash with order. Add V.A.T. 600V 115p. BC109C 0.11 723C D.I.L. 0.80 174003/4/5 0 08
Orders under a plus 12p P. & P. SUBMINIATURE VERTICAL PRESETS -01W only: BC147/8/9 0.10 747C D.I.L. 0.85 1E4006/7 0.08
ALL at 6p each: 50 El, 1000, 22013 4700, 680 n , 2.5M, BCY70/71/720.13 748C D.I.L. 0.38
BRIDGE/
5M. 1k11, 2.2k13. 4.7k11, 8-8k , leko, 15k0, 221E0' BFX86/87/88
47911, 100k0, 2500, 680k0. 1910 020 5Watt Audio I.C. WO1
100V
IA
0 -SO
COMPONENTS GALORE. Pack of 500 PLEASE ADD 10p POST AND PACKING ON ALL BFY50 0.18 TBA 800 21-50. WOO IA
mixed components manufacturers surplus plus ORDERS BELOW £5. ALL EXPORT ORDERS ADD
COST OF SEA/AIRMAIL.
SFY51/52
0C28
0-12
046
Dalt free with
every order. 80017 on
fall out. Pack includes resistors, carbon and PLEASE ADD 8% V.A.T. TO ORDERS
W.W., capacitors, various, transistors, diodes, Send S.A.E. for lists of additional ex -stock items. 3°NC236546 9°150 D.I.L. SOCKETS
trimmers, potentiometers, etc. Wholesale price lists available to bona Ode companies. 3
32N2133050 0414 00131
3-
009
BZ EZ:Y3788R513%-

1 Watt 6.8-
Send II plus 15p P. & P. C.W.O. To: MARCO TRADING 2143442
14 -Pin
1140 16 -Pin 0.14 200V 6% 016
Dept. EI, The Old School, Edstaston, 2143773 92.20 L.E.D.
/CASCADE C ONENTS COMPANY Er. Wem, Shropshire T1P41A 074 All prices 209-Ned 0'17
Ba n khead Farm, th Queensferry, Tel.: Whisall 464/465 (STD 0948 72) 40636 11-00 include V. 4..T. L. E. D. Clip 0-02
(Proprs.: Minicost Trading Ltd.
West Lothian C.W.O. PLUS P.P. 10p TO
BETA DEVICES,
R.T. SERVICES T75) 263 THE RIDGEWAY, ENFIELD, MIDDX.
BRAND NEW COMPONENTS BY RETURN,
Electrolytics, 15V, 25V, 50V-0.47, 1, 2.2, (MAIL ORDER ONLY) die0 125 1 0 2 OIL
4.7, 10 mF, 4p; 22, 47, 4i111 (50V, 5p); 100, 77 Hayfield Rd., Salford 6, Lancs. RED !19p
SOCKET
15p 5
3411; (SOY, 7P); 220, SP; (50V, fp). Subminiature
bead -type tantalums 0.1/35V, 0.22./35V, 12 Volt I Amp Trickle Ch £1.85 P.P. LEDs GREEN 27p 133p
pin
UPpin
0.47/35V, 1/35V, 2.2/35V, 4.7/35V, 10/16V, FM Tuner with R.F. Stage and A.G.C., wIn Date
133p
14
lap
22/16V, 47/6V, 100/3V, Sp. Mylar Film 100V 3 transistors, neg. earth, 21 x lx 14 in with clp, 1p YELLOW 27p
0.001, 0.002, 0.005, 0.01, 0.02, 2111; 0.04, 0.05, circuit, [1.37I inc. P.P. INFRA -RED 550µW axial lead 49p,
3p. Mullard Tubular Polyester 400V E6 Crouzet Geared Motors, 30 r.p.m. New,
series, 0.001-0-022, 3p; 0.033-04, Ip. Mullar E154 inc. P.P. LEDs with Data 1.5 mW T046, E1 -1
miniature C333 ceramics E.12 series 2% 1.8pF UHF TV Tuners. Transistorised, £1.65 OPTO-ISOLATORSimin Oat. pls. AMPS
47pF, 24p; 56pF-330pF, 3p. Polystyrene 83V inc. P.P. IL.74 1.5kV, 150kHz t1
709 all 29p
E12 series 10pF-1000pF, 21p; 1200pF Panels with I.C's on 74p per I.C. min. 4350 2.5kV, 5MHz £2.25 741 8 pin 30p
10000pF, 3}p. Miniature Highstab Carbon Film order 10 I.C's. 748 D.I.L. 36p
Transformers. 7.5V -1-7.5V 4A, LI inc. Infra -red LED and Photo -Tr or Diode
Resistors 4W E12 series 5% 10-10it13 (10% P.P.
up to 2500V isolated input output Vanv r16%
over 131.0), 1p. Postage Sp. Prices VAT I2 -0-12V, 100mA, 5110 inc. P.P. 9-0-9V,
nclusive. THE C.R. SUPPLY CO., 127/ 100mA, LI .10 inc. P.P.129V 50mA,85p inc. P.P. 7805 Reg t1.50
Plastic 1.5 Amp
2E3055 41p 7400
BHA 0002 15 W
10p
Chesterfield Road, Sheffield, S8 ORN. 6-0-6V, 100mA, L110 inc. P.P. 2E3702 12p
Brand new Boxed Rola Celestion Re- ,.. 263704 12p I.C. AMP (2.50
AC127 t7P 71543 25p
3 mos. M.C. Meters MIS (53p). First 0 rade. entrant Speakers SD 25 with 100V line trans- AC128 ...1.5P MPF102 40p 15914 3p
Panels 7 z 1251n, 11 ir 13In former fitted 150 without transformer 414 AF117 "P 2143819 M.. 1045,121
5p
Paaolln s 5/111. a for SOP: I s Bin. 6 for C1, inc. P.P. BC107 9 2E3823 30; Op
444-0 n. 3 for El, post paid. T.V. Convergence Panel. 2 12p 184004 7p
AC120. 3 Mugged colls. 3 slide switches. 11 W.W. Pots.
Transformer. 20 volt, I amp, LI10 P.P. BC108
BC109C 14p used OC/34 1144145 OP
3 carbon presets. 2 ferrite chokes. etc.. 01.10, op. Valupeks. Transformer. 45 volt, 2 amp, 82'75 P.P. BCY70 15p 10 for Sep 0047 6p
P0. 100 aimIca caps. 70p. cp. Send 10p for lists of others Pot Cores. LA( 225. Brand new. 4 for BCY71 22p 0081 7p
plus panels. etc. Refund on purchase E I '10 P.P. BCY72 12p MINISONIC! 0091 5p
7 lb assorted components C1.75, c.p. P.C. Board. S/S, 54 x 51in, 10 for 85p inc. P.P. BEY50 UP Buy all 741s 0A95 Sp
3EG I Scope Tubes with base and con- 0071 lip 0A200 6p
J.W.B. RADIO nections, 13 inc. P.P.
2E706
2N2904
10p
16p
send 27p each 00202 7p
a Penfield Crescent. UM, Cheshire M33 1NL Transistorised Timer. Variable delay. 110 2E2906 16p TELE TENNIS KITS post free.
Postage in brackets Mall order only or 250V A.G. input. With instructions. 7p
Brand new,a inc. P.P. Size r X 2" x 2".
Power Unit Components Transformer.
2142926(11)
26252816)
2E3053
129
19v
Seml Conductors, [12.75.
Sockets, f3-50. Order both f16
RESISTORS, 4W Carbon Film, Type UPM 050
Ip each plus VAT, post free. GREENBANK 18 volt amp F/W bridge rectifier, 2 1250
I PRICES INCLUSIVE - 10p P & P (1st class)
ELECTRONICS, 94 New Chester Road, mfd capacitors, all new EI.25 per kit. P.P.
lectrolytic Capacitors 4,000 MF ISLAND DEVICES, P.O. Bob 11, Margate, Kent
Wirral, Merseyside, L62 SAG.
A.G. DELCO BUZZERS 12V, 100mA approx.
TURN YOUR SURPLUS capacitors, transistors, Ixed Pack of C280 series Mullard capaci- }in. Dicer blade terminations, II5p each post
etc., into cash. Contact COLES-HARDING inc. P.P. paid. CWO. FELLOWS, 1 Park Crescent,
it CO., P.O. Box 5, Frome, Somerset. anels each wit type Nixie tu Doveridge, Derby, DEC 5NE. Tel. 088-93
Immediate cash settlement. N El 654inc. P.P. Min.. order 4. 3060.

Practical Electronics January 1975 /1,14,, 89

 SERVICE SHEETS for over 6000 models of
DRY REED INSERTS Televisions, Radios, Transistors, Stereo, Tape
SERVICE SHEETS Recorders, Record Players, etc., at only 30p,
plus S.A.E. with free Fault -Finding Guide.
Over 50,000 sheets in stock for 10,000 models.
Overall length 185' (Body length I1'). BELL'S TELEVISION SERVICES for service S.A.E. enquiries. Catalogue 20p plus S.A.E.
Diameter 0 14'. Max. ratings 250v D.C. and sheets, manuals, books on radios, T.V.s, etc. HAMILTON RADIO, 47 Bohemia Road, St.
500 ,oA. Gold clad normally open contacts. 69p Service sheets 40p plus S.A.E. Free book lists Leonards, Sussex. Telephone Hastings 429066.
per dozen; L4 12 per 100; 00.25 per 1,000; on request. Back issues of P.NV., P.E., E.E.,
£275 per 10,000. VAT and post paid.
G.W.M. RADIO LTD. TV available 25p plus 7p post. S.A.E. with
40/42 Portland Road. Worthing, Sun. 0903 34997 enquiries: B.T.S. (Mail Order Dept.),190 Kings SERVICE SHEETS, Radio, TV, etc. 8,000
Road, Harrogate, Yorks. Telephone (0423) models. Catalogue 20p. S.A.R. enquiries.
55885. TELRAY, 11 Maudland Bank, Preston.

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As long as you can understand the technical cap-
abilities of our advanced equipment then we can
train you to sell it.
The training is tough, so are our standards, that's
why we are only looking for those who can be highly
professional in this specialised and individual field
of selling.
As well as a technical background in electronics we
are looking for good organisation ability and plenty
of self motivation.
In return we offer excellent opportunities to develop
into management. Benefits include a Cortina 1600
Estate.
Write to your potential boss-W. Fergus Roy, Sales
and Marketing Director, A. Gallenkamp & Co. Ltd.,
Christopher Street, London EC2P 2ER.

Europe's largest laboratory supply house

gallenhami)
90 Practical Electronics January 1975
 MEN ! YOU NEED, TVCOMPREHENSIVE
£70 p.w. REPAIR MANUALS
can be yours Colour TV 2-ITT/KB to 1973 plus foreign: inc. Sony, Nordmende, etc.
Colour TV 1 -All other British manufacturers models to end 1973.
Jobs galore! Tens of thousands of Mono TV 1 -British sets to end 1973 covering from Alba to Ultra.
new computer personnel needed over Mono TV 2 -All Philips, Pye, Ekco and RBM models to end of 1973.
the next few years alone. With our Mono TV 3 -Due winter. Main British and Foreign portables used in UK.
revolutionary, direct -from -America, Full money back assurance. Thousands of faults -hundreds of models. All written
course, you train as a Computer in a practical, easy to follow symptom, cause and cure style. Invaluable to amateurs
Operator in only 4 weeks! Pay and students as well as to practising engineers. Written for minimum use of instru-
prospects? £3,500 -I- p.a. You know mentation. £3 each (P. & P. 35p under 4).
you can rely on us as we are the only SPECIAL OFFER TO READERS: First two mono and colour for
computer school recognised by the
Government backed National Com- COLOUR TV SIGNAL INJECTOR. A portable instrument capable of replacing both
puting Centre. oscilloscope and colour bar generator. Traces quickly and simply faulty components.
After training, our exclusive ap- etc. Complete manufacturing instructions with full operating procedures. Manual
pointments bureau - one of the price £l.20 (P. & P. 10p), printed circuit 75p post free. Easily made in under an hour.
world's leaders of its kind - intro-
duces you FREE to world-wide
opportunities. Write or 'phone
TODAY, without obligation.
TV TECHNIC PUBLICATIONS
London Computer Operators Freepost, Larkhall, Lanarkshire, Scotland ML9 1BR
Training Centre Y31, Oxford Hse. No postage needed
9-15 Oxford St., W.1. Tel. 01-734 2874

METER REPAIRS. Ammeters, voltmeters MISCELLANEOUS

multi -range meters, etc. Send to METER,
REPAIRS, 21 Mount Road, Thundersley, PSYCHEDELICATESSEN
Benfleet, Essex, 887 1HA.
is the only way to describe the paradise
FLUORESCENT of FREAKY gear now available from Boffin.
FOR SALE LIGHT Kits
LOOK!

SEEN MY CAT? 5,000 items. Mechanical and

KIT NO LICENCE EXAM. Transmitter/
Receiver 16.90
Electrical Gear, and materials. S.A.E. K. R. Variable -rate, BRIGHT -FLASH, Pocket
WHISTON, Dept. PE, New Mills, Stockport. Mini -Strobe £2.90
Ready -Made Experimental Modules
You can build this reverse polarity proof
Maxi -Volt SPARK GENERATOR (I inch
VALVES, VALVES AND MORE VALVES. light for use in homes, garage., dere.., for spark), 15,000 Volts. 11.90
camping, or emergency lighting. Everything is Mini DREAM -LABORATORY £3.20
Large stocks 1930-1974, many obsolete. Also supplied: the tube, white enamelled metalwork, SENSITIVE non -anatomical electronic
available many types of transistors and styli. first quality components. P.C.B., Instructions, etc. STETHOSCOPE £3.20
Price lists available 15p. COX RADIO, The Price only £3-19 Electronic 'VOICE -THROWER' L320
Parade, East Wittering, Sussex. West GHOST -HUNTING AID L320
Wittering 2023. Ready built £3-78 PEOPI.E DETECTOR
Diffuser only 59p extra SPEAK-THRU-WATER-FONE £6.40
PSYCHEDELIC MEDITATION AID 13.20
B EAUTIFUL P.E. "GEMINI" AMPLIFIER all
components as specified by designers in
ALUMINIUM Bird -Watchers' REMOTE MONITOR
Psychological
Device
CROSS-EYED EARS
£3 .20

1.1540
recommended cases built and working,
Buyer Collects.
£40.
Tel. 0702 77189 evenings. BOXES 'Big Ear' SOUND -CATCHER £3.20
(All prices include VAT, packing & postage)
Box 57.
Send remittance to:
P.E. SYNTHESISER PROJECT. Brand new BOFFIN PROJECTS
unbuilt keyboard and most components 4 Cunliffe Road, Stoneleigh
available. Send S.A.E. for details. FRANK Ewell, Surrey
MORTON, 65 Malmsey House, Vauxhall , (Mail order U.K. only)
Street, London, 8E11 SLU. Or for more details, send 20p for lists, plus
Oren. nor to: - free design project sheet
ELECTRONIC DESIGN ASSOCIATES
DEPT PE
P.E. JAN. 1968 TO JULY 1974 (4 missing)* 82 Bath Si Walsall, WS1 3DE. Phone 33652
Offers. Tel. Egham (Surrey) 2234. AERIAL BOOSTERS S3. We make three
types of aerial boosters:
L45-UHF625,
SOLATRON DOUBLE BEAM OSCILLOSCOPE. Add 10p P. 6 P. for orders under E2.
L12-VHF405, L11 -VHF radio. TELE-
Data. end circuits where *WO - VISION VALVES. Most types. Any 5 4b p.
Type CD1400 incorporating amplifiers. Type S.A.E. leaflets. LANCASHIRE MAIL-
CX1441 bandwidth to 15 Mc/s. S85 O.N.O.
Maidenhead 31339.
SINTEL oriels. supplied with orders, or
available separately 14Ip stamp ORDER, 6 William Street, Stubbins, Rams -
each). bottom, Bury, Lancs.
3 Digit DIP LED calculator display 11.25 - VAT - El 29
High Quality 0.3In LED 7 seg. display 95p VAT = XI 02
E AGLE K1400 AVOMETER for sale. New, PAK59250N Mane Clock IC E1110 - VAT = Y7 45
under guarantee, 632. Write J. MVERE, 208 Bend for our new simple MX502504 circuit diagrams
Soldercon IC socket pins - 300 pins for tt 40 o VAT = 21.52
Sussex Gardens, London, W2. 1,000 pine for MOO - VAT , £4 32
M5502505 4 0 DL7010 3In LED's 110.20 - VAT = £11.01 "'"'" TREASURE TRACER
Complete circuits and special prices for MK50250P4 with LED's,
MInItrons or SP352 s.
31n. OSCILLOSCOPE home built but little used, !UNTIL, 53B ASTON STREET, OXFORD. Tel (08651 43203 MK III Metal Locator
820. Bramley, Eastville, Eastfteld, Pickering.
Tel. 73270 W/Es only.
PRINTED CIRCUIT MANUFACTURERS offer Varicso tuning
LADDERS any P.R. Project P.O. ready drilled. One Britaln a best selling metal locator kit
Price 65p. Also P.C. production,
C.W.O. II Weighs only 2201
Speaker and earphone operation
Design, Art -Work and Photography under- Knocks clown to only tnin
LADDERS, timber and aluminium. Tel. taken. Send basic circuit, P.C. layout or P.C. III Prebuilt search coil assembly
Telford 586644 for brochure. Master stating quantity required for estimate I0 Five transistor circuit
by return or Phone: W.K.F. ELECTRONICS, Thoroughly professional finiah
You only new] soldering iron, screwrInver
Dept. P.C., Welbeck Street, Whitwell, Work- pliers and snips
BOOKS AND PUBLICATIONS sop, Nott'a., S80 4TW. Telephone Whitwell M seen on BBC -1 & BBC -2 TV
(Derbys) 695.
You are worth more
ELECTRONICS MEN.
than a measly £40 or £50 a week. Last year I THE CHIPS ARE DOWN!
clock chip now 23.95 inc. VAT, post free.
AY -5-1224 digital --- £9.80
P a P 44,
nci guaranteed
P a P .41
£13.75
-
earned £3,600 for six months work, the other r1

six I had off. You could do similar, my booklet Circuit and details S.A.E. GREENBANK MINIKITS ELECTRONICS, 35g LANGLEY DRIVE,
explains how. It's 65p from ALBEN, 3 Church ELECTRONICS, Dept. 320, 94 New Chester WANSTEAD. LONDON Ell 2LN (Mall Order Only)
Street, Dies, IP22 3DD. Road, Wirral, Merseyside, L62 5AG.

Practical Electronics January 1975 91

MORE RANGES FOR
fibree ©Mk suppliers
MARE S TAILS. Build a decorative display with this AMERICAN HI -POWER
LESS MONEY! professionally finished unit. 221n diameter with 7.000
fibres Looks immaculate 89.70.
AC/DC Multimeter type U4324 .
FIIIROFLEX SIZE 1. Flexible 440 wend glass light conduit.
A -DC 0-06-3A-6 Pongee.
bundle die 1 14mm asp per metre In per 10m) LOUDSPEAKERS
FIBROFLEX SIZE 4. 2 20mm bundle die [1.50 par metre
A -AC 0-3-3A- 5 Ranges.
V -DC 0.6-1203 V-9 Ranges. 4.L. (212 per 10m1 These powerful loudspeakers are
V -AC 3-000 V- a Ranges.
..

CROFON 1610. 64.euand plastic light conduit, bundle dia. ideal for disco, organ, P.A., guitar,
Frequency In the range of 45 to ...., Li.1.
0mm. 0 D 3 3mm 11 .20 per metre 111.30 per 10r111
IC OPTICAL MONOFIRRE. For multiple illumination etc., and are available in 8 or 16 ohm
Resistance: 500 ohm to
20Ithtz. )i''.7f-",,''....... -...,---"
5 Mohm-5 ranges. Decibel, -10 4. % ''. from one source. displays. internal illumination. effects, versions. The 'C' types incorporate
to «12413. Accuracy: z-2- 5%. DC 4 optical coupling. etc
..4% AC. Dimensions: 167 x 96
FP2I7 (0 5mm dl. )-50p per 10m. Ea per 100th
FP40 (lnffn die I-22.20 per 10m. Eli per 100th
an aluminium centre dome which
x 63mm. FP60 11 5mm die. I -El per 10m. 230 per 100m extends the treble response.
Only £8 85 OPTIKIT 103. Contains 2m Croton 1610 plus 5th each FP20,
SUPERTESTER 680 R ICE
FP40, FP80 plus polishing compound A handy pack for
the experimenter £4.70.
M I2A. 12" 50W R.M.S. £19.50
......-,-- ? .. 20.000 Ohm per Volt sensitivity LENSES AND REFLECTORS. We stock a range of 6 lenses M I2C. 12" SOW R.M.S. L21.00
,
-

-3".. , 1,- ... Fully weaned against external and 5 reflectors for use in proximity detectors. Intruder
M 15E. 15" 100W R.M.S....
1

_,-1- .''--v magnetic fields Scale width detectors. batch counters. tachometers. short range 1.32.40
and small can. dImensiona 1126 - optical communications.
'' -
-...3.'F.t-it-z- --.":-.-',..7-i--
-- - ' -- 95 - 32mmi Accuracy and
ty 11% in D C . 2% in AC.)
OPTIKIT Le. 1 each of 6 tense.. CZ SO.
OPTIKIT RIM 1 each of 5 reflectors. 01 50.
M I5C. 15" 100W R.M.S.... E34.00
Please state whether 8 or 16 ohm
I

I of indicated reading Simplicity CIRCULAR POLARISERS. Cut that glare Reduce specular
_
and ow of use and readability reflection by up to 20 . -enh anca contrast on crte. LED required when ordering.
Fun ranges of accessories displays. nixie,. Instruments. etc Available In recl,mberi
1.000 tones overload Printed green neutral 50mm square 110p; 15mm [1.20: 150mm Le
circuit board I. ,ornovel without £18.50 LINEAR POLARISERS. For light valve.. stress analysis. All prices include V.A.T. and
de.soldering Mitre ranges than any
other meter Ask for fres catalogue Accessories Extra type 11932 Type 0942 is for high temp use In projectors. carriage.
Use a pair to make a psychedelic light show Price as for
Accessories available to convert Supertester 680R circular polarise,. Mail order to:
into following' SIGNAL INJECTOR. GAUSS METER. LIGHT SOURCES AND DETECTORS: MV54 Miniature
12mrn) Red LED. 20p 110. lapl. MLED500 T092 Red LED.
ELECTRONIC VOLTMETER. AMPERCLAMP. TRANSIS-
TOR TESTER. TEMPERATURE PROBE. PHASE
SEQUENCE INDICATOR -Send for details.
20p 110. tap). MLED92 infra -Red Emitter. 30p 110 27p).
XC209-R 3mm Red LED. 20p 110* lip). XC209-Y or -G
N. M. MUSIC
Yellow Green 30p 110 21p), 2N5777 High Sensitivity
Photodarlington Silicon Detector. gain x 2.500. 50p
36 Ipswich Road Debenham
ALPHANUMERIC NIXIE TUBES 87911 (10« 45p). 84RD150 Silicon Photoiransistor-high speed. Stowmarket Suffolk 1P14 6BH
The Alphanumeric 4us good sensitivity 70p (10 17p)
NIXIE tube has the
ability to display
NEW MLS203. Latest Motorola Light Activated SCR.
High sensitivity tOrnW.cm.. high current 400mA OA peak).
all the letters of 00V Switch small motors or relay direct from optical SLOW SPEED MOTORS required (about 1 r.p.m.)
the alphabet .
control. up to 24W power [1.20110' I1.10) any quantity considered. Phone Mr. SMITH,
numerals 0 thru 9 SEM/ ULTRASONIC TRANSDUCER. For remote control
and special 40kHz Tx,Rx pair. [3.50.
061-633 3527.
characters in a Please add 9% VAT to prices above
single tube
Send sin v 8In S.A.E. for short form list. HARDWARE. Comprehensive range of
From the stand screws, nuts, washers, etc. in small quantities,
point of both read
ability and elec- FIBRE OPTIC SUPPLIERS and many useful constructors' items. Sheet
trical characteris- aluminium to individual requirements,
tics the Alpha
numeric NIXIE tube provides many unique benefits
(Dept. PE), P.O. Box 702 punched, drilled, etc. Fascia panels, dials,
including * 17V -21m4 * All d c operation * Uniform. London W10 8SL nameplates in etched aluminium. Printed
continuous line characters of equal height * Memory circuit boards for this magazine, and other
with simple solid state drive circuits * Readability in individual requirements, one-off's and small
high ambient light 200 footlamberts brightness
CLEARING LABORATORY, scopes, recorders,
runs. Machine engraving in metals and
* Long life with no loss of brightness * Character plastics, contour milling. Send 2 4fp stamps
height 2/in bridges, audio, R.F. generators, forcatalogue. RAMA R. CONSTRUCTOR
Bases for above 50p each turntables, tapeheads, stabilised P.S.U.s, sweep SERVICES, Masons Road, Stratford on Avon.
Price only 99p each plus 16p P./P. generators, test equipment, etc. Lower Deed- \Varwicks, CV37 9NE.
ing 236.
JUST ARRIVED!! P.C. BOARDS FOR THE P.E. CCTV ENAMELLED COPPER WIRE
NUMERIC INDICATOR TUBES CAMERA S.W.G. 115 Reel ;lb Reel
Ultra -long lifia, high quality, 0-9 and 2 independent deci- Manufactured from highest grade glass fibre 10-14 [1.90 [1.05
mal points Supply voltage 200V do Current 14mA. material, drilled, roller tinned and ready to 15-19 [2.00 [HO
Pulse duration 100.4 Character height 0 51. overall 20-24 [2.05 [1.15
assemble. [3010 [1.20
size 1 4. PCB1-1110 plus 9p VAT. 25-29
Brand new. guaranteed Surplus to manufacturer a 30-34 [2.20 EI.28
requirements. Type /3585310
PCB2-90p plus 7p VAT. 35-40 [225 11.35
Or supplied cut to size but undrilled, [1.25 the All the above prices are inclusive in U.K.
1-25 £1.00; 25 + 90p; 100 -, 80p; pair plus 12p VAT. All Post Eree.
COPPER SUPPLIES
1,000+ price on application. WASCO ELECTRONICS 102 Parrewood Rd., Withington, Manchester 20
35p POP
Queen Street, Lancaster LAI I RX Telephone 061-224 3553
Add a% VAT to all Items .-

ELECTRONIC BROKERS LTD.

49-53 Pancras Road, London NW1 20B P.C. ETCHING KIT P.O. AMPLIFIER UNIT
Contains 100 so in copper laminate board. Dab etch resist Contained in steel case 5/ - 5 3/in are 2 GET115 tran-
Tel. 01-837 7781 pen lib ferric chloride. etching dish abrasive cleaner, sistors on heat sinks. 3 pot cores. 2 30V caner., 4 audio
and instructions all for only t3, 30. transformers. 1% resistors and Capacitors With circuit
RESISTORS AND CAPACITORS diagram, E1.
AUDIOSCAN, the "do-it-yourself" speaker 500 ASSORTED RESISTORS. 11 .35; 2.500. O. 200 poly. 71b BARGAIN PARCELS
mail-order specialists. High fidelity speaker mica. ceramic capacitors. El. 250 hi -stab resistors, 1%, 2% Hundreds of new components-pOts, resistors, CapaCitOre
kits, chassis units, sound 4tbsorbent, grille and 5%. 81.20. 15 different airspaced and compression switches plus P.0 boards with transistors and diodes. Also
loads of odds and ends Contents always changing as new
fabric and much more. Send 7p in stamps for trimmers up to 1.250pF. El.
stocks arrive Amazing value at 82-30.
bargain list to: AUDIOSCAN, Dept. 4 VEROBOARD
Princes Square, Harrogate, Yorkshire. 'too sp in assorted sues and pitches. About 8 pieces, t1-10. COMPUTER PANELS
3W TAPE AMPLIFIERS 31b assorted tl -40; 7Ib 82-65; 5615 E15. Pack containing 500
Polished wooden Cabinet to 13 v Sin containing a sensi- components. including at least 50 transistors. 90p. 12 high
tive (20uVI 4 -valve amplifier with tone and volume controls. quality panels with power transistors. trirnpots. ICs. etc..
SUPERB INSTRUMENT CASES by Bazelli, 3 watts output to the 7 v 4in 30 loudspeaker. Also a non- 22 - SO. Pack with 20 trirnpots plus other parts, El. Pack with
manufactured from heavy duty P.V.C. facei standard tape deck. Supplied in good working condition 24 FCH181 or (MC1818), El.
steel. Hundreds of radio, electronic and hi -ti with circuit. Standard mains operation. EC 50. Suitable MISCELLANEOUS
enthusiasts are choosing the case they require cassette. E1.10. Spare head. 33p. Tape (ex -computer), Transformers III mains prix I. 18-0-16V with 9V tap at 1{A.
75p. Amplifier chassis only. complete and tested (2 E2; 6-0-6V at 10OrnA. asp; 9-0-9V at 100mA 90p, 12-0-12V
from our range of over 200 models. Generous ECC83. ELBA. EZ80) and speaker. O. at 100mA, 95p. Balanced armature earpiece. use as mic
trade discount. Prompt despatch. Free lit- VERSATILE POWER SUPPLY or spkr 200. 30p. tin dos crystal mic insert. 35p. Silicon
erature, BAZELLI, Department No. 23, St. Contains mains transformer. 2 amp thermal cut-out and gr 2ot tube. 60p: 1/14001 10.50p; 194004 10 Kip; 194007
Wilfrid's, Foundry Lane, Halton, Lancaster, bridge rectifier in neat plastic use Will give 1 7-10 5V 1011; SC40D Triac El; 22000F 25V tip. AC127. 128. 151. 178.
LA2 our. output with 2 extra capacitors (provided). Supplied com- 187. 188, all 20p; BC107, 108. 109. 10p; 293055 Sip; 741C 35p.
plete with data sheet Only 21.20. FERRIC CHLORIDE
Anhydrous technical quality to Mil -spec in lib double sealed
Lighting Modules and Kits Bought
SPECIAL OFFER OF 741s packs lib 80p; alb MX; 101b t4.45; 1001b 233.
Direct From The Manufacturers Full spec. solldev devices 8 -pin DIL Good range of Multimeters in stock from [3.50.
SOUND TO LIGHT: 3 x I kW channels with 10 for £2.60; 25 for £5.75; 100 for SURPLUS COMPONENTS AND EQUIPMENT WANTED
bypass, sensitivity and dimming controls. This FOR CASH.
unit was designed for use by hire firms and has £21.
proved to be very reliable. All prices quoted include VAT and postage (mainland only) S.A.E. 11.1, nquirle
MODULE (ready built), 116.99. KIT, [14.99.
DIMMERS: 2 -way wallmounting units, 89p.
THEATRE AND DISCO/CLUB DIMMERS
CUSTOM BUILT
GREENWELD ELECTRONICS (PE10)
Med Order Dept., wholesale/retail shop: 51 Shinny Perk Road, Southampton S01 4FX (Tel. (0703)
Written enquiries and Mail Order only to:
SELEKTRON 772501). Other retail shops et: 21 Deptford Broadway SE8 (Tel. 01-6922009). and 38 Lower Addiscombe
21 Priors Road, Windsor, Berke. SL4 4PD - Road, Croydon (Tel. 01-688 2950)

92 Practical Electronics January 1975

 Build the Mullard C.C.T.V. Camera KEYBOARDS
ONE OF Kits are now available with compre- 4 -OCTAVE WITH CONTACT ACTUATORS
hensive construction manual (also £16 incl. VAT. Carriage £1.50
JOSTY EUROPE'S
available separately at 80p).
LEADING SEND 5" 7" S.A.E. FOR DETAILS TO: BARRY M. CHILDE
CROFTON ELECTRONICS ELECTRONICS MART
ELECTRONIC KITS 124 Colne Road, Twickenham 370 Charminster Road, Bournemouth BH8 9RX
Middlesex TW2 6QS

Post free Mail Order 12 VOLT 21in 13 watt FLUORESCENT

S.A.E. For Catalogue GADGETS GALORE!! LIGHTING (by THORN/AE)
Alarms-Test Gear-Musical Instruments with diffuser and on off switch.
Timers-Audio-Disco-Sound Effects
TELEVIEW
Ideal. caravan, boat.
* READY BUILT AND TESTED * emergency lighting,
Sample prices: Signal Injector El .95 etc.
Signal Tracer L2.95
414 CATCOTE ROAD PRICES INCLUDE U.K. POSTAGE C550
Guaranteed
HARTLEPOOL AND BATTERIES Inc VAT end post.
CLEVELAND Mai: Order Only S.A.E. list to: List price t7112 Inc VAT
G. K. SERVICES
83 Westdale Road, London SE18 3BQ h`bgre F6FIPPetTury Shropshire

C.W.O. PLEASE. POST AND PACKING

YATES (FLITWICK)
ELECTRONICS
LTD.
PLEASE ADD 10p TO ORDERS UNDER Ll.

Catalogue sent tree on request, 10p

stamp appreciated.
DEPT. PE, ELSTOW STORAGE DEPOT
KEMPSTON HARDWICK, BEDFORD PLEASE ADD 8% VAT
RESISTORS M ULLARD POLYESTER CAPACITORS C280 SERIES
1W and 1W PIHER.
fW 1% ELECTROSIL 250V P.C. mounting: 0.0IµF, 0.015µF, 0.022pF, 0-03314F, 0.047µF, 34p; 0068µF, 4p ;
Power Values Price 0.1µF, 44p; 0.15µF, Sp; 0.22µF, Sip; 033µF, 7p; 0-47pF, 9p; 068µF, 12p;
1.0µF, 141,p; 1.5µF, 22p; 2.2µF, 16p.
watts Tolerance Range available 1-99 100+
5% 4.70-2.2M0 E24 I -3p 1.1p MYLAR FILM CAPACITORS 100V
10% 3-3M 0-10M0 E12 I.3p 1.1p CERAMIC DISC
1.0_,m. E24 3.5p 3p 0 00 I µF, 0002µF, 0005µF, 001µF, 002µF, CAPACITORS
1,1p,; 1 0-3-9 0 I.3p 1.1p 3p. 004µF, 005µF, 0068µF, 1µF, 6p. 100pF to 10,000pF, 2p each.
i4 S/
10%
4.7 0-IM 0
1 0-10 (1
E12
Ell
I.3p
Hp
1.1p
7p
Quantity price applies for any selection. Ignore fractions on total order. ELECTROLYTIC CAPACITORS
(µEN) 1/63, 1-5/63, 22/63, 33/63, 47/63, 68140, 6 8/63, 10/25, 10/63, 15/16, 15/40.
DEVELOPMENT PACK 15/63, 22/10, 22/25, 22/63, 33/6-3, 33/16, 33/40, 47/4, 47/10, 47/25, 47/40, 68/6-3,
0.5 watt 5% Piher resistors 5 off each value 4.7 0 to im O. 68/16,100/4,100/ I 0,100/25, 150/6.3,150/16.22n/4,220/6 3,220/16,330/4, 6p. 47/63,
E12 pack 325 resistors L2.40. E24 pack 650 resistors 14.70. 100/40, 150/25, 220/25, 330/10, 470/6-3, 7p. 68/63, 150/40, 220/40, 330/16, 1000/4,
10p. 470/10, 680/63, I 1p. 100/63, 150/63, 220/63, 1000/10, lip. 470/25, 680116,
1500/6.3, 13p. 470/40, 680/25, 1000/16, 1500/10, 2200/63, 18p. 330/63, 680/40,
POTENTIOMETERS 1000/25, 1500/16, 2200/10, 3300/6.3, 4700/4, 21 p.
Carbon track 5k 0 to 2M 0, log or linear (log 1W, lin 1W).
Single, 14p. Dual gang (stereo), 49p. Single D.P. switch, 29p.
SOLID TANTALUM BEAD CAPACITORS 12p
SKELETON PRESET POTENTIOMETERS 01µF 35V 2-2µF 35V 22µF 16V
0.22µF 35V 4.7µF 35V 33µF 10V
Linear: 100,250,500 0 and decades to 5M 0. Horizontal or vertical P.C. mounting 0.47µF 35V 6.8µF 25V 47µF 6.3V
(0.1 matrix). 1-0µF 35V 10µF 25V 100µF 3V
Sub -miniature 0.IW, 6p each. Miniature 0.25W, 7p each.

TRANSISTORS VEROBOARD JACK PLUGS AND SOCKETS

AC107 16p BC109 14p 81)115 75p BF337 46p ZTX300 1/3p
0.1 015 Standard screened 32p 2.5rnm insulated 13p
ACI 26 21 34 26p 28p Standard insulated ISp 3.5mm insulated 13p
18p BC115 16p 801 16 60p BEY50 22p ZTX302 20p 24 R 5 28p 28p Stereo screened 44p
AC127 lap BC116 15p BD124 81p BFY51 lip ZTX34 1 lap 31x34 lap 28p Standard socket 15p
3.5mm screened
2.5mrn socket
22p
14p
ACI 28 18p BC! 17 23p 80131 60p BFY52 22p ZTX500 18p 34p
ACI41 K 22p BCI 25 15p BDI 32 64p BRY39 elp ZTX503 25p 17 24 Stereo socket 22p 3.5mm socket 14p
AC142 25p BC142 24p 80140 9534p
P 77p
66p MJE340 47p 2N2646 60p 17 x 34 130p 108p D.I.N. PLUGS AND SOCKETS
ACI 65 20p BC 1 43 21 p BDY32 57p MJE370 68p 2N2904 28p 17 x 34 (plain) 86p 71p 2 pin, 3 pin, 5 pin 180°, 5 pin 240°, 6 pin
AC176
ACI87
AC188
ACI 93K 28p
18p
22p
22p
8C147
BC148
BC! 49
12p
12p
Ilp
lap
BF I 15
BF158
BF I 59
32p
lip
lip
0C26
0C28
0C35
90p
90p
90p
2N2905
2N2926
2N3053
32p
lip
3Ip
17 x 24 (plain)
21 x 5 (plain)
21 x 34 (plain)
-- 51p
lip
ISp
Plug lip. Socket 8p.
4 way screened cable, 26p/metre.
6 way screened cable, 3Ip/metre.
BCI53 BFI60 23p 0C42 16p 2N3054 60p Pin insertion tool 62p 62p
AD140 53p BCI54 lap BFI61 26p 0C44 12p 2N3055 60p Spot face cutter Sip BATTERY ELIMINATOR
ADI43 73p BC157 ISp BF164 lip 0C45 12p 2N3702 15p Pkt. 50 pins 20p
52,p
20p
LI.70
9V mains power supply. Same size as PP9 battery.
ADI49 70p 8C158 15p 8E173 lap 0070 lip 2N3703 14p
ADI61 42p BCI59 14p 6E177 29p 0071 lip 2N3704 20p
ADI62 42p BC' 69 15p BFI 78 43p 0072 12p 12N3705 20p
AF 14 15p BC171 13p BFI79 41p 0075 12p 2N3706 19p HIGH VOLTAGE TUBULAR CAPACITORS -1,000 VOLT
AF 15 25p BC! 72 22p BFI80 42p 0081 12p 2N3707 20p 0.0IµF Ilp 0047µF 16p 0.22µF 28p
AF 16 25p BC 177 20p 15F18 I 31p 0082 Ilp 2N3708 2.0p 0.022/1F 14p 0.1ttF 20p 047µF 36p
AF 17 25p BC! 82 15p BF 1 82 41p OCP71 35p 2N3709 19p
AF 18 50p BCI82L 16p BF I 83 43p ORPI 2 65p 12N3710 19p POLYSTYRENE CAPACITORS 160V 24%
AF 21 50p BC183 15p BFI 84 32.p TIP29A 49p 2N3711 19p
AF 26 50p BC I 83L 16p BF 1 85 32p TIP30A sap 2N38 I 9 32p 10pF to 1,000pF Ell Series Values, 4p each.
AF 27 SOp BC184 lap 13E194 14p TIP3 I A 62p 2N4062 25p
AF 39 33p BCI86 25p BFI95 17p TIP32A 74p 40360 46p
AF 78 48p BC187 25p 8E196 15p TIP33A 98p 40361 43p SMOKE AND COMBUSTIBLE GAS DETECTOR-GDI
AF 80 50p BC2 1 2 I3p BFI 97 16p TIP34A 148p 40362 45p the GDI is the world's first semiconductor that can convert a concentration of
AF 86 39p BC2 I 2 L ISp BF200 40p TIP4 I A 79p 40363 88p gas or smoke into an electrical signal. The sensor decreases its electrical resis-
AF239 48p BC2I4L 19p BF259 25p TIP42A 90p 40406 44p tance when it absorbs deoxidizing or combustible
BC107 I3p BCY70 2Ip BF262 26p TIP43 35p
such as hydrogen, carbon
40486 90p monoxide, methane, propane, alcohol, North Sea gas, as well as carbon -dust
BC108 13p 130112 52p liBF263 26p ZTX108 lap containing air or smoke. This decrease is usually large enough to be utilized
without amplification. Full details and circuits are supplied with each detector.
Detector GDI Li. Smoke and Gas Detector Kits, mains operated with audible
ZENER DIODES WIRE WOUND POTS. 3W, 10,25 slarm L5.60. Mains operated Meter Indicator L7.90. Mains/Battery Gas Leak
400mW 5% 3-3V to 30V, 12p. 50 0 and decades to 100k 0, 50p. Detector L12.60. 12/24V Battery operated L8.40. 12V Battery operated Two
Remote Sensors E12.80. NOTE. The battery operated kits incorporate our
patented circuit to minimise battery drain. Typically 120mA for 12V. These kits
DIODES contain all parts required with the exception of case. Suitable case mains operated
RECTIFIER SIGNAL kit 1140. Battery operated kits LS.
BYI27 1250V IA 12p 0A85 7p
IN4001 50V IA 7p 0A90 5p PRINTED BOARD MARKER 97p
1N4002 100V IA Bp 0A91 5p Draw the planned circuit onto a copper laminate board with the P.C. Pen, allow to
I N4004 400V IA Bp 0A202 dry, and immerse the board in the etchant. On removal the circuit remains in high
I N 4006 800V IA 10p 1N4148 Sp relief.
I N4007 1000V IA 10p BA114 8p

Practical Electronics January 1975 93

 EDUCATIONAL
SINCLAIR CALCULATORS

TELEVISION
TRAINING
Cambridge Memory £20.115 (E1.95)
16 MONTHS' full-time £15.15
Solve your communica-
Cambridge Assembled
Sinclair Scientific
£15.115 (V '55)
122.45 (C205)
practical and theoretical train- tion problems with this Executive with Memory [25 - OS (F2 49)
4 -Station Transistor Intercom system (1 master and
ing course in Radio and TV 3 Sobs). In robust plastic cabinets for desk or wall
Servicing (Mono and Colour) mounting. Call/talk/listen from Easter to Subs and
Subs to Master. Ideally suitable for Business, Sur-
FERRANTI ZN414
IC radio chip with data C120 (22p) Also available kit
for beginners. gery, Schools, Hospital, Office and Home. Operates
on one 9V battery. On/off switch. Volume control.
of extra parts to complete a radio (2.45 (42p) Send
S.A.E. for free leaflet
Complete with 3 connecting wires each 66ft and
13 WEEKS' full-time Colour other accessories. P. dr P. 00p.
MAINS INTERCOM (new model) SINCLAIR PROJECT 80
TV Servicing course. Includes
No batteries -no wires.Just plug in the mains for AFU £8 30 (73p)
-
,
100 hours practical training. instant two-way, loud and clear communication. Z40
Z60
C512 (63p)
(6.30 )73p)
On/off switch and volume control with lock system. !.
Mono revision if necessary. Good Price 628.76 per pair. P. A P 60. extra 016
PZ5
£7.21 (80p)
£511 (63p)
:r

electronics background essential. PZ8 C7711 (847)

INTERCOM /BABY ALARM P28 C736 (62p)
Decoder. U.75 (84p) Trans. for P78. £3 -IS (50p)
NEXT SESSION commences on Tuner, [11.621[1.371 Stereo 80. C11 -62(C1 37) Project
805. [21115 (C2 80) Project 805S0. t33.95 (f3-10)
January 2nd.
Prospectus from London Elec- ECONOMICAL
QUADRAPHONICS
tronics College, Dept. AI, 20 £6.50 Introducing the Napole ` fr-,
Penywern Road, London SW5 Same as 4 -Station Intercom for two-way Instant
communication. Ideal as Baby Alarm and Door
OAIO self-contained matrix
quadraphonic synthesizer.
9SU. Tel. 01-373 8721. Phone. Complete with 66ft connecting wire. Just feed the output of any
stereo system (including Project 80 or 601 into it and
Complete with battery. P. A P. 40p. hook on 4 speakers to obtain the latest experience in
lians,st,TELEPH tt AMPLIFIER sound. Send S.A.E.for free leaflet Only C10.15 1C1 10)

WANTED
£6.45 SINCLAIR
Why not boost SUPER IC12
business effi- 6W rme power
TOP PRICES PAID ciency with this incredible Telephone Amplifier. With 44 paps
NEW VALVES AND TRANSISTORS Take down long telephone messages or converse booklet and ......
without holding the handset. A useful office aid. On/ printed circuit
Popular T.V. and Radio types off switch. Volume control. Complete with battery. C1.110 140p)
,,,

P. A P. 30p. Full price refunded if not satisfied In 7

KENSINGTON SUPPLIES (B) dark,
367 Kensington Street WEST LONDON DIRECT SUPPLIES (PE/I)
169 KENSINGTON HIGH STREET, LONDON, W.8 NEW SINCLAIR IC20
Bradford 8, Yorks. Nigh power IC audio amplifier WM (C1.05)

DELUXE KIT FOR THE IC12

COMPONENT KITS NOW AVAILABLE. Includes all parts for the printed circuit and volume.
bass end treble controls needed to complete the mono

111111301111C 4ip STAMP BRING

ALSO FOR "POWER SLAVE" DETAILS.
DETAILS. ASK version C1.70 (26p) Stereo model with balance control
£3.70 (43p)
IC12 POWER KIT
Supplies 28V 0 5A C217 (52p)
TRANSISTORS VOLTAGE POWER SLAVE
LOUDSPEAKERS FOR THE IC12
BC204
BC 182
Imp REGULATORS
BC209C Ilp µA7815
10p 723
220p
180p
P.C. B's
Designers Layout
Master Board
Stabiliser
6165
LIAO
SCOOP Sin 8 ohm [1.30 (29p( 5in x flin 8 ohm C1,115 (377).
PREAMP KITS FOR THE IC12
BCI84 Imp ARRAYS
BC212
BC2I4
14p ML3046P
16p CA3096AE
75p HUTCHINSON Exclusive to Eaton Audio. Typo 1 for magnetic pickups. mics and tuners. Mono
model. [140 (25p). Stereo model. C250 (337). Type 2
12.0p TONE CONTROL
BC213
BC213L
15p
151/ OP. AMPS (with data sheets) PE minisonic demonstra- for ceramic or crystal pickups. Mono. 70p (19p)
Stereo. C1.40 (24p)
Few only at 95p
ZTX300 15p
ZTX500 17p
709/13 Dip
710/T05
39p
39p
37p
tion cassettes. Hear the SEND S A E FOR FREE LEAFLET ON KITS
2N2484 24p 741
2N2904 30p
2N2905 27p
748
FETMOPA
41p
450p
sounds produced at the BATTERY ELIMINATOR BARGAINS
2N22I9 22p
2N3054 100p
SPECIAL
PURPOSE
Please add 13 to
final total of order
Audio Fair 1974. C20 Mono The most versatile battery
eliminator ever offered.
High Voltage Switched output of 3. 4t.
MPSLO I 39p
LIN EARS
5G3402N 174p Cassettes. 6. 7+. 9 and 12V at 500mA.
MP51.51 41p SG3402T 174p TRANSFORMERS E3.90 (57p).
MPSUO7 69p
MPSL157 83p
SG 1495D
MFC6040 100p
290p 220/240V Pri.
Min. type.
ill I S each inc. VAT & postage Other eliminators stocked
250mA-3 way switched
SDT9203150p MFC4000B 70p 0-12; 0-12V e 6VA model going 6. 7+ and 9V.
FETS 0-20; 0-20V @ 6VA POTENTIO- CAPACITORS (245 (S5p)
2N3819 46p T.T.L. L1.84 each METERS Tubular Electra. 14p 50mA-43V. C1-115 (40p) 6V.
2N5459 60p 74001 29p 0-19, 25, 33, 40, 50V [1 95 (40p). 9V, el -OS (400.
7402N 38p MIN MOULDED 25V. 25µF; 47µF 7/V cassette type. [2.50140p). Double 4+V . 40. £2-7S
DIODES qn 500mA £1.35 CARBON 100AF 16p, 470µF 29p
IN5401 2Ip 7404N 2.7p
24p
0-17.5V rd I.6A 1.2.73 24mm dia. 1000µF 46p (43p) 6V + 6V £2.7S (43p) 9V 9V, £2.75 (43p)
-.-

IN914 Sp 7410PC 0-25V 2A +0-25V 2A 50y. 1000µF 57p 500mA-Heavy duty deluxe models 6V. C2 -7I (55p)
8A1 48 25p 7420N 2.4p
23p 63V. 10µF 22p 7/V. C2.711 (55p) 9V. 12.711 (55p)
15150 12.p 7430PC LINEAR 5k ft; 10k O; IOW 24p
I GP7 10p 7473N
48p HEATS1N KS
75p 25k13; 50k O; 100k n ; S-DECS AND T-DECS
7475N Marston type for IN. PRINTED CIRCUIT
NOISE 7476N 49p POWER SLAVE 65W ELECTROLYTIC S -DEC Mal (31p)
DIODES 7489N 660p and 100W versions. 4-7/40V; 10/63V T -DEC £3.113 (47p) 1
Z11 53p 7493PC 89p 82.85 each LOG. 10k 25k O; 22/40V; 47/40V
;
u -DEC A [3.991517) 1
-..... 4,
ZIM 12.0p 741211 85p Type 154 for T05 50k 0 all at 2Ip each NW OW ,0 of , .
74122N
RECTIFIERS 74I23N
BOp
144p
9p each GANGED. 100kCI
13p each
I 00/63V; 470/ I 6V
u -DEC B
IC carriers 16 dil-plain
(150) With socket. rl 77 .
..,616r/
..../
,..,

REC41A 110p 74150N 210p

lin; 5k(1 log; 10k0 13p each 917
REC46 255p CONSTANTAN log. all at 78p each (25p). 10 TO5-plain. lop
REC70 40p RESISTORS WIRE HIGH RIPPLE (15p). With socket. MPS
003 ohms/cm as TYPE (24p)
EA 100/10 2% METAL Experiment guides -A. C1-50 (26p). B. C1.77 (29p:
100p OXIDE 16p for S specified for the PRECISION 10 3300µF 63V 8220
MDA942A/1 5% CARBON POWER SLAVES. TURN 7100oF 40V 75p C. 90p (18p). D. 12.40 (35p). E. E4-20 (53p)
210p FILM 9p for 5 20cm lengths 10p I k ft R.S. TYPE L3.40 I 0000µF 40V 6144
TERMS: MAILORDER SWANLEY ELECTRONICS
EATON AUDIO
P.O. BOX 3, ST. NEOTS
ONLY. C.W.O.
Cheques or P.O.'s pay-
able to Eaton Audio.
Orders over L5 free of
At\
Buy it with Amer
P.O. Box 68, Swanlay, Kent BR8 8TO.
Please add the sum shown in brackets after the price
to cover the cost of post and new VAT
PAP. Otherwise please Official credit orders from schools. etc welcome
HUNTINGDON PE19 3JB add 10p in the LI. No VAT charged on overseas orders.

94 Practical Electronics January 1975

 MAPLIN ELECTRONIC SUPPLIES *ScAME
CDAGY
ORGAN BUILDERS SERSVICE
Keyboards: High quality adjustable type MES announce the very latest development in organ
Sloping front 61 -note C to C. 118.50. circuitry.
Sloping front 49 -note C to C. 114.35. THE DM02
Flat front 48 -note F to E. 614.35. 13 Master Frequencies on ONE tiny circuit board.
Contact blocks GB -2 (2 make contacts), 22p. LOOK AT THESE AMAZING ADVANTAGES
Palladium earth bar per octave length, 13p.
Stop tabs rocker type not engraved (white. * 13 frequencies from CS to C9. * Each frequency
red, grey or black) with DPDT switch, 49p. digitally derived from a SINGLE h.f. muter onclllator.
Gold clad phosphor -bronze contact wire per * Initial tuning for the WHOLE ORGAN: ONE
yard, 30p. SIMPLE ADJUSTMENT. * Relative tuning NEVER
DRIFTS I * External control allows Instant tune-up P.E. SOUND SYNTHESISER
BASIC ORGAN CIRCUIT to other musicians. * Outputa will directly drive most
types of dividers including the BAJ110. * And each If this project seems expensive YOU HAVEN'T SEEN OUR
Leaflet MES 51 shows a complete circuit for a bask fully output can also be used sw direct tone source. * Vari- PRICES!
polyphonic organ. Send only 13p for leaflet and start building able DEPTH AND RATE tremulant optional extra. We are stocking all the parts foe this exciting project. from the
now! REMEMBER -when you have built this organ you will * Gold-plated plug -In edge connexion. * Complete special I.C.'s right down to the nuts bolts and spacers for
later be able to use the same top quality component parts as the fibre glass board (Including tremulant if required) ONLY mounting the Veroboards
basis of a large sophisticated instrunwrz with all the facilities 4.51n. * Very low power consumption.
3.71n. x Sendpre lists
you want. V.'atch our ads for details. * EXTREMELY ECONOMICAL * S.a.e. please
LEAFLET MES 52 shows how to extend your MES 51 basic PRICE. * Ready built, tested for lull technical
organ to two keyboards with lots more stops. Just send 5p and fully guaranteed. details.
(stamp) with an S.A.E. and we will send you a copy. DMO2T (with tremulant) ONLY E.T.I. SYNTHESISER
61466. Prods enquiries
REVERBERATION UNIT DM02 (without tremulant) 21E26. welcome.
We stock all the pans for the "Electronics Today International'
Enhances the sound of any electronic musical instrument. SAJ110 7-etage frequency divider In one 14 pin DIL synthesiser including all the P.C.B.'s required and all the
Ready built spring line driver module suitable for use with almost metalwork including a drilled and printed front panel for a truly
package. Sine or square wave input allows operation professional finish.
any series line. £534. from almost any type of master oscillator including the Some of the circuits in this brilliant design are entirely original.
Two types of spring line available: DM02 (when 97 notes are available). Square wave

7'
Independent authoritative opinions agree the E.T.I. International
Short line. C305. outputs may be modified to saw -tooth by the addition Synthesiser is technically superior to practically all synthesisers
Long line. 1759. of a few components. 8AJ110: 0363 each OR special available today.
S.A.E. please for details. Leaflet MES 24 price for pack of 12: 12600. S.a.e. please for data sheet S A.E please for our detailed price list,

CAPACITORS PLUGS AND SOCKETS WE KNOW YOU NEED IT !

The MES 1074
Sub -miniature CATALOGUE
Axial lead electrolytic IS STACKED
Mid V Price Mfd V Price with dozens of lemplin,
1 63 6p 68 6. 11p new lines
1.5 63 6p 68 16 6p 11 Fk
22 63 6p 68 63 14p with clear dillsir..14on.
3a ea 6p 100 4 Op Mid V Price and detailed 4.,;.,
4.7 63 6p 100 10 OP 470 6.3 6 WE RF WAITINt. It
88 40 5p 100 25 6p 470 10 14p EL SH IOC A COPS
1 mill
6.8 63
10 23
Op
6P
100
100
40
63 16p
6p 470
470
25
40
16p
25 .T0 with
he
tee
I SIPRE %SO 0
POST 1 -12F1 -
10
15
63
16
6p
Op
150
150
6
16
OP
OP
680
680
6.3
16
lop
lap DIN PLUGS MAINS R50 way chassis Sid j stereo plug
((/ ordering
hs
*Astern EX( ITFD
our Siti 3, AI t, F dis-
,tunt sounchem. ST At.t.F.RED
15 40 Op 150 25 6p 680 25 23o 2 pin 1 flat)
1
8p P314I 3 pin I .5A socket iggp Plastic lip to our L N BF AT A BI F speed
13 63 6p 150 40 14p 680 40 'Sp 3 pin Op chassis plug with Screened 30p
22 10 Op 150 63 16p 1000 4 14p 4 pin. 5 line socket. Per mono socket of Ner, ice Take the first
lop PHONO step towards teal sets ice
22 25 ap 220 4 6p 1000 10 080'1. 5 pin B pal 30p 10p: Moulded
Plug plastic "
NOW. Send ()NI1
22
33
69 6P
6.36p
220
220
10
16
6p
6p
1000
1000
16
23
25p
28p
040'1. 6 pin 19p SrA 2190 3
chassis plug
pin SA
22p
Plug screened
Chassis socket
99
12p mono socket +" with
2 break contacts for our beautiful),
duced c,tiologue
23p
r-
33 16 6p 220 25 14p 1500 63 16p SA 1862 Line socket 41) 14p: Moulded stereo
33 40 op 220 40 16p 1300 10 25p for above 25p socket 1." with 3
47 4 6p 220 63 25p 1500 16 20p
DIN Sockets
2 pin JACK break contacts 11p: and leave the
47 10 6p 330 4 6p 2200 63 25p 3 pa, 4 pin. " MeMLIRDO Std. mono 3 5mm plug plastic
47 25 6p 330 10 Op 2200 10 28p A 1130.1.
5
pintan
B RP8 8 way chassis
5 Plastic
Pl3,ug
1 9p: screened 15p; rest to us!
47 40 6p 330 16 14p 3300 11.3 040°1. V. 6 pin 9P 52p Screened 21p open socket lip.
47 68 6p 330 63 38p 4700

LINEARS POTENTIOMETERS
CA3046 Transistor array 69p OMNIUM GATHERUM
LH0042C. T099 (1051. FET tip Op Amp 1.425 PP3 6 etc baiter, clip dual min 9p.
.

LM30IA. 8 -pin DIL. Op Amp 39p PPI. V. etc.. battery clip separate per pair 6p.
MC13031. 14 -pin. Stereo Preamplifier 11.39 Pair crocodile clips. red. I black insulated
1
Rotary miniature carbon track r epindle
MC13101s, 14 -pin DIL. FM Stereo Decoder (no coils needed) 11'50 sleeve 10p.
MFC4000S. OW Audio Anp 75p Solder Multicore 22 s.w.g. 10 metres 23p Single gang Lin or Log
MFC6040 Electronic attenuator gap Silicone grease in special dispenser 20m1 54p. 5k. 10k. 25k. 501t. 100k. 250k.
MFC8010. 8 -pin case. IW Audio Power Amp 1131 Terminal Block 12 -way 5,1 14p. 500k. IM 2SA land ik Lint lip
MFC9020. 10 -lead case. 2W Audio Power Amp II 37 Probe clips spring loaded per pair 30p.
NE555V. 8 -pin DIL. Precision Timer OOp Panel fuse holders 20mm 20p (gin 4lp.
NE561B. 16 -pin DIL. Phase Locked Loop 14.48
SGI49513. 14 -pin DM. Four Quadrant Analogue Multiplier 1.2711 Tramlormen
Amplifier/Multiplier 61.69 LT700 min output transformer Pri 12k0
isA723C. TO99 (705). 2 to 37V Voltage Regulator 75p
Sec Si) 200mW 50p.
pA723C. 14 -pin DIL. 2 to 37V Voltage Regulator 75p Selwnssin. Mane Tranalermer Single gang with DP so itch
pA74IC. 8 -pin OIL. Op Amp Dual gang
36p 6-0-6V 100mA 95p, 12-0-12V 50rriA 93p. 250V IA Log or Lin n to 2M
I,A741C. 14 -pin DIL. Op Amp (Stereo) without
43p Size Both appros 30 x 27 x 25mm as above
pA747C. 14 -pin DIL, Dual Op Amp 11.05
switch Log or Lin 33p.
giA748C, 8 -pm OIL, Op Amp 311p Min. Males Transformer 51t to 2M as
ZN414. T05. TRF Radio 11 .26 Sire- 46 x 31 x 38mm above Hp.
Full data. pin connexions. etc.. on nearly all types above in our 0-12V 250mA 0-12V 250mA 1139.
catalogue. Price 25p. Sub -miniature° 1W
Maim Tramformor MT3AT Vert or Boris
Pri 200-220-240V Sec. 12-15-20-24-10V 100. 250, 500. lk,
1A 3.60.
510TCHES Pri 200-220,240V Sec
Maine Troulormer AfT3IMAT
0-15-20V IA
2 5k. 5k, 10k. 25k.
50k,
500k.
100k.
IM
250k,
7p
Rotary with adjustable stop pole 2 to 12 way; 2 pole 2 to 6 way; 0-15-20V IA MIN.
1

3 pole / to 4 way; 4 pole 2 or 3 way. each 36p.

Illook-up wire. 7 strand 0.2mm. PVC covered

RESISTORS
Mains rotary DPST 250V 2A. 211p.
tinned copper wire for light general connexions
Slide sip 10 1.4A II colours- black. blue brown.
Sub -miniature preen. gre y. orange. pink.violet. white.
DPDT yellow 10 metres of any one colour 20p. Pack
of 11 11 of each colour) 10m. coils 12.00. Carbon Film OW 5% 111 to 121; 10% 12M to 1035 E12 to
Single con screened Sp per metre.
Carbon Film 4W 5% 111 to 100; 10% 12M to 10M Ell Ip
Push to make
Twin individually screened 1151p pee metre
Carbon Fib. 4W 5% 11 CI to 910k ElI 0 E24 Ip
non -locking
High quality single screened 500 100pF per Carbon Film 1W 5% int) to 10N Et? 30
14p High quality "sub -miniature" metre. ideal for high Lade audio connexions
Metal Oxide 4W 2% 10 0 to 1M El2 & E24 4p
toggle switches. 151p per metre.
WI. -mound 2*W 10% 0 22obma to 047obina E12 lip
Toggle 750V 1.5A SPDT I .5A 240V a.c. 58, Wirewound 24W 5% Johns to 270okma Ell I2p
with ON/OFF DPDT 3A 240V a.c. 77p Makin 3 -core subminiature IA black PVC
E32 value, 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 and decades
plate 25p. Four Pole DT 3A 240V a.c. covered 19 strand OArnm per conductor lip E24 values 11. 13, 10, 20. 24, SO, 315, et 51, 62, 75. 91 and decades
11.37 per metre

. Post and Packing FREE in U.K. catalogues to MAPLIN

Orders and enquiries for catalog
EEsLiEeCIT TR.01 Rayleigh,
VAT tPoletahseeflandadl teotkal. (15p handling charge on orders under El) NSolCuthSeUndP-PontlISEet OP1.0°2.441110; 3.
!Fleet clams past pre -/0.1d envelop* supplied free tenni...pry order

Practical Electronics January 1975 95

 COMPLETELY ELECTRONIC

NUJ CD NO MOVING PARTS

CHANTICLEER
* READ: TIME AND ALARM
* ELECTRONIC 'BEEP' ALARM TONE
* TEN MINUTE 'SNOOZE' FEATURE
* BRIGHT, CLEAR DISPLAY
* NO MOVING PARTS
* EXECUTIVE STYLING
* SOLID STATE RELIABILITY
likvmummir
Digital clock Alarm
The heart of the CHANTICLEER is a tiny electronic Has a.m. or p.m. setting with alarm on/off indicator. A
package containing thousands of transistors which divide gentle electronic 'beep' tone with special snooze feature
the 50 cycles/second mains frequency into precise time that resets the alarm for ten-minute intervals. The snooze
units. The clock "movement" in fact has no moving parts is activated by simply tilting the clock forward and then
to wear out or tick or tock or hum or click. releasing. Upon cancelling, the alarm can be immediately
reset for the same time next day.
RECOMMENDED VAT BYWOOD ELECTRONICS
PRICE 219295 EVIED 181 Ebberns Road
Hemel Hempstead
Herts. HP3 9RD
Tel. 0442 62757

G. F. MILWARD, 369 Alum Rock Road, Birmingham B8 3DR. Tel. 021-3272339

TUB!!!
12 VOLT FLUORESCENT LIGHTING R esistBRANors-wire-wound and

II
carbon
* Capacitors-silver-mica. paper,
+ ceram polyester and
electrolytic.
Controls-volume, pre-set.
_ .
ca
Disilicon, germanium.
adrebs o-nwre
2ener.
Transistors-silicon. germanium.
104. All the above are new and unused
stock
INVERTER TRANSFORMERS 13/15W 70p VOLTS i E e p I
(CIRCUIT INCLUDED) weight. all are different in content.
T.C. and contain
"CURRENT ECONOMY'' TRANSISTOR (600 ma.) 50p ponents from the above list This
MAXIMUM LIGHT'' TRANSISTOR (1.3A) 50p gte
46 is a fantastic. unrepeatable offer
that will enable you to get a good
RESISTORS/CAPACITORS TO SUIT 15p stock of spares at a tiny traction
LAMPHOLDERS (LONG LEAD) 30p PAIR of normal price'
To make things even more interest.
(SHORT LEAD) 20p PAIR ing-TWENTY OF THESE BAGS
WHITE ENAMEL CASE, 18in or 211n (POSTAGE 30p) 70p NEW IMPROVED ALSO CONTAIN A POUND NOTE
CIRCUIT! TWENTY CUSTOMERS WILL BE
TUBE, 18in-15W or 21in-13W 45p VERY PLEASED INDEED
(NOTE: TUBE ONLY SUPPLIED IF CASE ORDERED, TO And the price that we are asking,
Drives 21in 13W Only El -50 including both postage
PREVENT POSTAL DAMAGE) and VAT'
13W FITTING READY BUILT AND TESTED-INCLUDING TUBE 18in 15W Rush your order now' This offer
(POSTAGE 30p) £3.75 or adaptable for is only made to reduce our surplus
stock' It is unlikely that in these days
POST/PACKING, 25p PER ORDER EXCEPT WHERE SHOWN 2 x 12in 8W of rising prices we shall ever be
able to repeat'

100 i-; WATT RESISTORS 1 VEROBOARD CUTTER 20 ASSORTED UNUSED

1
100 CERAMIC
CAPACITORS
100 DIODES
£1 5552i in
1

so ins
VERO
. in x 0 15 BOARDS
ODD PIECES - £1 MARKED. TESTED
TRANSISTORS
BC10a ETC.
£1 ..,S,VAPI,V.E.R4',:llti OF
INDUCTORS. RESISTORS
A CAPACITORS
POSTAGE 25p PACK No 1
POSTAGE 25p I PACK No 3 POSTAGE 25p PACK No 5 POSTAGE 30p PACK No

100 RESISTORS 100 RESISTORS 1 TRANSISTOMISED 100 RESISTORS

1 100 CERAMIC
CAPACITORS
100 POLYSTYRENE
£1 100 CERAMIC
CAPACITORS
50 MULLARD POLYESTER
£1 SIGNAL TRACER KIT
1 TRANSISTORISED
SIGNAL INJECTOR KIT
£1 100 CAPACITORS
(ASSORTED TYPES)

CAPACITORS CAPACITORS
POSTAGE 25p POSTAGE 25p POSTAGE 25p POSTAGE 25p
PACK No 2 1 PACK No a I PACK NO 6 l PACK No 8

NOTE: ALL GOODS PLUS 8% VAT (EXCEPT OVERSEAS)

96 Practical Electronics January 1975

 Practical Radio - Electronics
Certificate course includes a
learn while you build
3 transistor radio kit.
Everything you need to know
about Radio Et
Over ISO Electronics
maintenance and

ways to repairs for a spare

time income and
engineer a -
a career for a
better future.

better future MECHANICAL

Society of
Engineers-
A N1 S F (Mech.) O
CUT OUT THIS COUPOBI
Tick or state subject of interest.
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DRAUGHTSMANSHIP
Institute of
Engineering
Designers
.em elm in

Construction
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I ngineers & General tall branches)
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find out how

Eng. Inspection l'ng.
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That's how long it will take you to fill in the coupon. Mail it today and Computer
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Others have done it, so can you Skills
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"Yesterday I received a letter from the Institution informing that my applica-
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 enrvgs SO MUCH MORE - AND YOU PAY
LESS VAT WITH HENRY'S LOW PRICES

You can build the Texan and Stereo FM

TEXAN 20 , 20 WATT IC STEREO AMPLIFIERS
Features glass fibre PC board. Gardners low field transformer, 6 ICA 10 tran-
sistors plus diodes. etc. Designed by Texas Instruments engineers for Henry s
(and P.W. 1972). Supplied with full chassis work, detailed construction handbook and all
necessary parts. Full input and control facilities. Stabilised supply. Overall size 15; in 2fin 6fin.
Mains operated. Free teak sleeve with every kit. 0000
£31.06 (G.B. post paid). BUILT AND TESTED f37.50.
3000
CALCULATORS 00,00
STEREO FM TUNER
Features capacity diode tuning. led and tuning meter indicators. stabilised power supply -mains operated.
0000

High performance and sensitivity with unique station indication IC stereo decoder. Overall size in teak sleeve Sinclair Cambridge Kit E13.50
Sin x 2fin x 6fin Sinclair Cambridge (Built) £17.511
Complete kit with teak sleeve [21.00 (G.B. post paid). BUILT AND TESTED £24.95. Sinclair Memory C22-50
Sinclair Scientific C26.95
Sinclair Scientific Kit [18.50
JOIN THE LARGE BAND OF HAPPY CONSTRUCTORS!

EMI SPEAKERS
TRANSISTORISED SPECIAL PURCHASE
SINCLAIR SPECIAL
PURCHASE
MODULES 13in x Sin chassis speakers (carr..
packing
ng301Peachor
TC OW 8 ohm
Sop
cone ,
Project 60 Stereo Pre -Amplifier
C675 P. & P. 20p
C2.20. 450 TC 10W 4,8. 15 ohm with Project '605 Kit E19.95 P. & P. 25p
Tuners -Power Suppliers -Amplifiers twin tweeters and crossover £3.95
each.
I.0 12 6W Amplifier C2.10 P. & P. 15p
EW 15W 8 ohm with tweeter £5.25
Amplifiers (All single channel unless stated) 350 20W 8. 15 ohm with tweeter
Polished wood cabinet
each C7.80
p 1490
4-300 9V 300mW 0/P 3-8 ohm, 1-10mV VP 1.75 (Parr., etc. 35p each or 50p pair) PORTABLE RADIO
2004 9V 250mW 0/P 3-8 ohm. 10-100mV i/P 2.70
104 9V 1W OiP 8-16 ohm, 10mV I/P 3-10 ACTIVITY COUNTER
304 9V 3W a P 4-8 ohm. 10mV I/P 3.95
555 12V 3W 0 P 8-16 ohm. 150inV I/P 4.10 Complete with Power Pack. 09-97
555ST 12V lfin 1+ in OrP 8 ohm. 150mV 5.95 P. & P. E1
E1208 12V 5W 0/P 4-16 ohm, 25-60mV i/P 5-10 PHILIPS 8 WATT
608 24V IOW 0 P 4-8 ohm. 30-50mV 4.95
410 28V IOW O P 8 ohm. 160rnV I/P 4,95 FLUORESCENT UNIT
620 45V 30W OAP 4-8 ohm, 15OrnV I P 9.95
Z40 30/35V I5W 0 P 4-8 ohm. 100mV I P 5.45 EXCLUSIVE PURCHASE DOSIEMETERS
260 45/50V 25W 0 P 4-8 ohm. 100-250mV I P 6.95
SA6817 24V 6 - 6 0,P 8 ohm. 100mV 4P 1020 Brand new Philips 12V operated OW fluorescent
tube units for standby lighting Complete with tube 0-5R 62P 45p each
and instructions. Price f3.50 (P & P. 25p). 0-50R 62p ,-
per dozen
0-150R
Amplifiers with controls
E1210 12V 2i. - 2+W 8 ohms 8 25
RE500 Mains 5W 4-16 ohms 6-30
SAC14 7 . 7W 8 ohms 1175
SAC30 15 + 15W 8 ohms 14.95 EXCLUSIVE
CA038 9V If + 15W 8 ohms 6.95
CA068 12V 3 . 3W 8 ohms 1050 5 WATT IC GRAVINER INFRA RED
AMPLIFIERS DETECTOR DESIGNED
FM Modules Special purchase 5W output. 8-16 ohm load. 30V FOR HEAT OR LIGHT
Mallard LP1186 FM tuner (front end) with data 10.7 MHz 0,P 4.85 max. d.c. operation complete with date. Price
Mallard LP1185 10.7 MHz IF unit with data 4.50 [1.50 each Or 2 for C2115. DETECTOR. CONTAINING
Gorier Permeability FM tuner (front end) 10.7 MHz 0-P 4.20 Printed Circuit Panels 50p.
931A PHOTO MULTIPLIER

FM and AM tuners and decoders UHF TV TUNERS AND GK45 AND

WORK, £3.50.
NET-
FM5231 (Tu 2) 6V FM tuner 7.95
TU3 12V version (FM use with decoder/ 7.95 625 line receiver UHF transistorised tuners FM
SC/4912. Decoder for Tu3-12V 7.95 U.K. operation. Brand new IF. 6 P. 25p each)
Stereo 14.95
TYPE C variable tuning C2.50. TYPE B 4 -button
SP62H 6V stereo FM tuner 4.80
M007 9V MW -AM tuner 11.95 push-button (adjustable) £3.50. AMTRON KITS
Sinclair 12,45V FM tuner stereo recorder for above 7.45
A1018 9V FM tuner in cabinet 13.95 AVAILABLLEX-STOCK.
A1005M (S) 9-12V stereo decoder FM for above 7.50
1062 12V stereo decoder. general purpose 6.50 STC AND ITT MINIATURE RELAYS SEND FO -R FREE LISTS.
1509 6V 2 p.c.o.
18OR 6/12V 2 p.c.o.
Preamplifiers 185R 12V 2 p.c.o. BRAND NEW JOSTY KITS
Sinclair Stereo 60 Preamplifier 6.75 12506 12/55V 2 p.c.o. 60p
01300 Cart. Tape Mic Inputs 9V 2.05 17006 18 24V 2 p.c.o. AVAILABLE EX -STOCK.
E1310 Stereo 3-30mV mat cart 9V 4.75 18008 21V 4 p.c.o. P. & P 15p
25008 18,24V 2 p.c.o.
FF3 Stereo 3mV tape head 9V 4.95
40009 24V 2 p.c.o.
SEND FOR FREE LISTS.
3042 Stereo 5-20rna Meg. cart mains 5.95
E025 Mono 3-250mV Tape/Cart Play 9V 1,95

INVERTOR KITS 40kHz ULTRA-SONICS

HENRY'S HOME ENTERTAINMENT CENTRES 15W [5.20 P r/IP 30p TRANSDUCERS 0.90. P. &
London: 40W 06.110 P & P 40p
354.6 Edgware Rd . W2 101-402 5854). 376/8 Edgware Rd., W2 101-723 0818) 372
Edgware Rd., W2 (01-402 8140) 120 Shaftesbury Ave WI (01-437 9692) 230 Tot- P. 25p.
tenham Court Rd . WI (01-580 1785) 144 Burnt Oak B way. Burnt Oak. Edgware
(01-952 7402) 190/4 Station Rd.. Harrow, Middy 101-863 7788)
Out of Town: PP9 BATTERY ELIMINATOR TAA 960 40kHz AMP. 0.75.
256 Banbury Rd , Summertown, Oxford ( (0865) 530721 Complete Kits of Parts including P/C Boards
55 Gloucester Rd Bristol 7 ( (0272) 457911 [1.95 Complete Kit P. & P. 15p.

SUPPLIERS OF ELECTRONICS FOR OVER 30 YEARS. 8% VAT TO BE ADDED TO ALL ORDERS. VAT -UK ONLY.

Henry's
ectronic entres
404-406 Electronic Components & Equipment 01 -402 8381 Hi Fi and
309 PA -Disco -Lighting High Power Sound 01 -723 6963 Electronics
RADIO 303 Special offers and bargains Store
All mail to 303 Edgware Road. London W2 18W
Centres Ope
9 am - 6 pm
EDGWARE ROAD, W2 Prices correct at time of preparation. Subject to change without notice. E.&O.E.