SPA-600 TSO INSTALLATION AND OPERATING INSTRUCTIONS
The Sigtronics’ SPA-600 is a voice actuated intercom with “transmit
through the aircraft radio capability” using your push-to-talk switch.
Three controls are provided:
Power Switch — Turns unit on and off.
Volume Control — Controls the intercom volume.
Squelch Control — Allows the setting of voice actuated (VOX) operation
of the intercom for variations in background noise levels and differences
in headset microphones.
OPERATING INSTRUCTIONS
I. INTERCOM MODE
A. Put on headset/s and position the boom mic close to the mouth, as
is the practice with a hand-held mic. Voice clarity is best when mic
is at one side of the mouth and 1/4” from the lips. Figure 1
B. Set audio panel to “Headphone” position, if applicable.
C. Turn power “on” and set Volume Control to a low level. (1/4th to 1/3rd
transmit switch on your yoke and your voice is automatically transmitted
open for best signal to noise ratio).
via the aircraft radio. (You will hear your own voice when transmitting via
D. To adjust the intercom SQuelch for voice activated operation (VOX),
the aircraft radio side-tone return, If the radio does not have side-tone,
it is helpful to have some background noise present. Turn intercom
then you will not hear your voice). (A minor modification to the intercom
SQuelch control all the way counter-clockwise. Now, without
will enable it to simulate side-tone).
speaking, rotate the SQuelch control clockwise until you hear the
background noise in your headset. Next, rotate it counter-clockwise a III. RADIO MONITORING — Radio monitoring is automatic. The radio
small amount and wait (approximately 1 second) until the background monitor circuit is always active; even with intercom power switch
noise disappears. Finally, make small adjustments until your voice “off”.
triggers the unit at comfortable speaking levels. This procedure is IV.SOLO FLIGHTS — Since the intercom is not needed during solo flights,
necessary because the squelch is a “Fast-on, Slow-off” system. it may be turned off. The pilot will still hear the aircraft radio, since
Once set, the intercom stays silent until someone speaks in their this circuit is always active, and the pilot may transmit to ATC via his
headset microphone (mic). Then it instantly turns on and relays the push-to-talk switch. (Co-pilot position cannot transmit when intercom
conversation. After about a second of no conversation, the intercom is off).
goes silent again.
Minor readjustment of the SQuelch may be necessary if the V. BACK-UP — If a problem is suspected in the intercom, simply turn it
background noise level changes significantly (such as from taxi to off. You will still receive the aircraft radio and will be able to transmit
take-off power conditions). from the pilot’s position. The hand mic may also be used, however, the
II. RADIO TRANSMIT MODE — Transmitting from both pilot and co-pilot Transcom should be turned off and you should unplug your boom mic
positions is possible on a one-at-a-time basis. The transmitting mic from the mic jack. (Leave headphone plugged in for radio reception).
disables all other mics. When you are ready to talk to ATC, depress the
CHASSIS INSTALLATION AIRCRAFT
The Sigtronics’ SPA-600 has been designed to mount either horizontally PANEL ����� ���
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or vertically in your aircraft panel. All necessary mounting hardware has
been supplied for a 6-way installation. (A round faceplate is also available
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from Sigtronics to fit a 2 1/4” round instrument hole).
HARDWARE SUPPLIED �� ��� ������ ������
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• Six Headphone Output Jacks — Accept standard .250” aircraft ����� ���� ���
headphone plugs.
• Six Microphone Input Jacks — Accept standard .206” aircraft � ���
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microphone plugs (i.e. amplified dynamic or electret). (U93 plug
compatible jacks can be used in place of the jacks provided).
• Mic Jack Insulating Washers: 6 shoulder and 6 flat. Figure 2
• Panel: Lettered on both sides.
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• Control Knobs (2), Switch Nut (1), 4-40 Screws (2) ���������
• Template: Hole size pattern for drilling aircraft panel. �������� ������
• Aircraft / Intercom interface cable (4 feet long) ��� ������ ����
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The location selected requires a minimum front panel area of 2-1/2” by ������
1-1/16”. Depth required behind panel is 4-3/16” plus cable access.
Caution: Move aircraft flight controls through limits of travel while ���
observing selected area to make sure rear of intercom and cable will not
interfere with aircraft control components.
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PANEL PREPARATION: ��������
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1. Position adhesive template on aircraft panel in selected area. �����
2. Center punch each hole at cross lines. (The five holes are in straight Microphone Jack Figure 3
line and equally spaced 0.4” apart.)
3. Drill 1/8” pilot hole all five places. 1. Remove nut from Transcom ON-OFF switch bushing.
4. Enlarge holes to 1/4” and 3/8” per template. 2. Remove knobs from Volume and Squelch controls. NOTE: DO NOT
MOUNTING CHASSIS: See Figure 2. REMOVE nuts from Volume and Squelch control potentiometers.
Sigtronics Corporation 3. Remove two 4-40 panel screws and remove panel from Transcom
chassis.
178 East Arrow Highway
4. Insert Transcom from rear of aircraft panel with appropriate arrow
San Dimas, CA 91773 pointing upwards.
Phone: (909) 305-9399
E-mail: info@sigtronics.com (continued)
Web Site: www.sigtronics.com
SPA-600
INTERCOM
SPA-600 Installation Drawing Figure 4
MOUNTING CHASSIS (continued)
Table 1
5. Install panel and lightly thread nut on to ON-OFF switch. Nuts and
washers on Volume and Squelch controls should fit inside the 3/8” Plug
diameter holes. Wire Color Function Connect To:
Pin #
6. Select two 4-40 screws through holes in intercom panel. Tighten ON- White / Ring Terminal of Pilot Intercom
OFF switch nut. 1 Pilot Mic Input
Black Mic Input Jack
7. Install knobs on Volume (VOL) and Squelch (SQ) control shafts using White / Pilot Transmit Switch Pilot Transmit Switch (PTT)
.050” Allen wrench. 2
Red *A Input (Switch to Ground to Transmit)
MOUNTING HEADPHONE AND MICROPHONE JACKS: Headphone - Radio and Radio Headphone Output and all
1. Select mounting areas. (One mic and one headphone jack for each 3 Blue *B
Intercom Outputs Headphone Jacks
headset). Again, make sure the jacks will not interfere with aircraft Hand Mic Jack Ground Terminal
control components. 4 Black *C Ground
(Point A)
2. Drill 3/8” diameter holes for headphone jacks and install. Tip Terminal of Aircraft Mic Jack
3. Drill 1/2” diameter holes for mic jacks and install with insulating Transmit Relay (Key)
5 White *D or Key Input of Aircraft Radio or
washers supplied. (See Figure 3). Control Output
Audio Panel
WIRING INSTRUCTIONS Ring Terminal of Aircraft Mic Jack
6 Brown Mic Audio Output or Input of Aircraft Radio
Connections should be made as shown in Figure 4 and indicated in Table
or Audio Panel
1
*A. White / red (pilot push-to-talk) must correspond with white / black (pilot 12 VDC through 24 VDC
7 Red *E Intercom Circuit Breaker
Power Input
mic input) as shown.
*B. The blue wire from Pin 3 must be connected to the aircraft radio Ring Terminal of Passenger #1
8 Tan Passenger #1 Mic Input
Mic Jack
headphone output- NOT the speaker output.
*C. Connect all intercom mic jack grounds to Point A as shown in Figure Ring Terminal of Passenger #2
9 Tan Passenger #2 Mic Input
Mic Jack
4. (Use black washers supplied to insulate intercom mic jacks from
aircraft chassis ground). White /
10 Copilot Transmit Switch Copilot Transmit Switch (PTT)
Blue
*D. Do NOT connect transmit switches to white (key) wire.
*E. Red wire may be connected to either 12 (14V) or 24 (28V) power source. White / Ring Terminal of Intercom Copilot
11 Copilot Mic Input
Orange Mic Input Jack
No switching or adjustments are required to operate from either
source. 12 No Connection
FINAL CHECKOUT AND ADJUSTMENT
Ring Terminal of Passenger #3
After the unit is installed, again check that the intercom chassis, jacks, 13 Tan Passenger #3 Mic Input
Mic Jack
and wiring harness are clear of all aircraft operating controls and cause
no interference with them. Check out the intercom functions by following Ring Terminal of Passenger #4
14 Tan Passenger #4 Mic Input
Mic Jack
the Operating Instructions.
15 No Connection
It may be necessary at this time to adjust the intercom mic output to
the aircraft radios. A small, square, adjustable trimmer potentiometer is * See Wiring Instructions
provided inside the unit for this purpose. It is accessible through a hole
in the side of the case, marked “Mod. Adj.”, and can be adjusted with a intercom or if a new radio is installed. (The output is set for unity gain at
screwdriver. In the event of over modulation (garbled) or reports of weak Sigtronics.)
transmissions over the aircraft radio, an appropriate adjustment can be Weight: Intercom with panel and knobs (4.6 oz.)
made. Clockwise rotation increases the output level to the aircraft radio Jacks and wiring harness (7.6 oz. maximum)
mic input. Counter-clockwise rotation decreases modulation level. This Current Draw: 0.07 amps @ 28 volts
adjustment sometimes needs to be made after initial installation of the FAA TSO: C50b ENV. CAT (DO-160) CFBBBX
spa-600.pdf 1-8-2007 Form SPA-600-IS REV F
