S12

RELAY INTERLOCKING
(Metal –Carbon Relays)
Introduction to Relay Interlocking
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 What is meant by Interlocking ?

• Interlocking is an arrangement between various functions like signals, points,

sidings, Track circuits, slots, LC gates, etc, operated from a panel or a lever
frame, so interconnected to operate in a predetermined sequence to ensure
safety.

• Interlocking is compulsory in signalling to ensure safety.

• Normally interlocking is provided and proved at least in 2 stages.

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 RAILWAY INTERLOCKING SYSTEM

The are different types of Interlocking Systems available like

1)Mechanical Interlocking

2)Electro Mechanical Interlocking

3)Electrical or Relay Interlocking

4) Electronic Interlocking System

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 Policy on Type of Interlocking to be adopted:

SI. No Type of Station Avg.No.of Routes Type of Interlocking to be provided

a) “C” class Station
b) Mid-section Interlocked LC gates
c) IBS/IBH
d) Stations on Double Line section without loop and
1 with one emergency X-over and/or siding Up to 10 Electronic Interlocking
e) Stations on single line Sections with one loop
f) Automatic Block Signalling with/without Mid-
Section Interlocked LC gate
Electronic Interlocking linked to Signal
2 Way-Station & Small Junction Stations 10 to 50 routes
Control centre if required
Electronic Interlocking with Distributed
3 Big stations and major Junction stations 50 to 500 routes
Architecture and/or Object Controllers

Route Relay Interlocking with metal to

More than 500 metal type relays OR
4 Very large stations/Junction Stations
routes Electronic Interlocking with Distributed
Architecture and Object Controllers

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 Types of Interlocking

S.No Type of Interlocking No of Stages How achieved

First stage At locking tray of the lever frame.
I) Mechanical Interlocking Second stage Near functions with Mechanical detectors
etc.
First stage At locking tray of the lever frame
Electro-Mechanical
II) Second stage By means of electrical controls on the
Interlocking
functions (EPD’s/TPR’s etc)
First stage At route checking stage(UCR)
III) Relay Interlocking Second stage At signal clearance stage(HR)
In EI Interlocking checked in Application Logic
IV) Electronic Interlocking First stage At route checking stage(UCR)
Second stage At signal clearance stage(HR)
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 Relay Interlocking Introduction

Relay Interlocking :
When the interlocking between various functions is achieved by means of
relays, then it is termed as Relay Interlocking.

The specification for relay interlocking: IRS S-36-87.

Types of Relay Interlocking :
(i)Non-Route setting Type or Panel Interlocking
(ii) Route setting type or Route Relay Interlocking

Note : Panel interlocking ---- Non-Route setting type

Route Relay interlocking ---- Route setting type

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 Differences between PI and RRI

S.No PANEL INTERLOCKING ROUTE RELAY INTERLOCKING

1 Non route setting type Route setting type ( NX system)
2 Route is set by setting the points Setting of route and taking `OFF’
individually and then the signals signal is done by pressing the route
are taken `OFF’ button concerned and by pressing the
signal button or turning the signal
switch to reverse simultaneously.
3 For smaller yards and way side For bigger / major yards
stations
4 Route buttons not compulsory Route buttons compulsory

5 CLS is optional CLS is compulsory

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 Differences between PI and RRI

S.No PANEL INTERLOCKING ROUTE RELAY INTERLOCKING

6 Sectional Route Release is not Sectional route release is provided for
provided normally better Flexibility.
7 Point knobs are of two position Point knobs are three position Type
(N-R) Type (if knobs are provided) (N-C-R) (if knobs are provided)
8 Emergency point operation is not Emergency point operation is
Compulsory. Compulsory.

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 Differences between PI and RRI

Note:
 As per subsequent & recent specifications, PI stations should also be
provided with route setting type feature.

 And the panel should be of Domino type with self restoring type buttons
and with automatic route release facility on complete arrival of a train.

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 Basic Requirements of Metal to Carbon Relay Interlocking

(a) Control cum indication Panel with switches / buttons, only self restoring type
buttons for operation of various functions. These functions i.e. Points,
signals, track circuits are represented geographically on the panel.

(b)Provision of Track Circuits with demarcations and fouling protection with

different colours on panel.

(c)In PI, points are provided with 2 position switches (N-R) and in RRI, 3 position
switches (N-C-R).

(d) All other switches are normally 2-position type.

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 Basic Requirements of Metal to Carbon Relay Interlocking

(e) In RRI, all routes with different overlaps will have separate route button and
they are marked alphabetically.
(f) Relays with metal to carbon contacts are used generally.
(g) Colour Light Signals are provided.
(h) Yard is track circuited completely between outer most stop signals in case
of PI and between outermost signals in case of RRI.
(i) Crank Handle, level crossing, siding, interlocking are through EKT/RKT.
(j) PVC 16 strand 0.2 mm dia flexible wire is used for relay wiring.

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 Basic Requirements of Metal to Carbon Relay Interlocking

(k) All indications of signals, points, track circuits and various other functions
are provided with 12V / 1.2 W lamps or LEDs.

(l) A stabilized 110V AC is used for signals and unstabilised 110V AC is for track
circuit feed. Battery 110V DC with charger used for point operation.

(m) A 24V Battery bank one each for INT, EXT and Axle counters with battery
charger is provided. When necessary more number of sets can be provided to
cater for the load.

(n) 12VDC/AC (or) 24VDC for panel indication.

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 Basic Requirements of Metal to Carbon Relay Interlocking

Power supply:
(i) Non Railway Electrified (NON-RE) Area: AC 230V,50Hz is drawn from station
feeder(Local) in addition two standby diesel generators are provided.

• RE D/L : Up AT, Down AT and Local

• RE S/L : AT, Local, One Diesel Generator

(ii) In big yards, DG sets of adequate capacity shall be installed in addition to

supply from ATs

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 Basic Requirements of Metal to Carbon Relay Interlocking

(p) Condition of Block section / Block Instruments on panel.

(q) In case of cancellation of a signal, a certain time delay is required to release

the route, provided the train has stopped in rear of the signal.

(r) Emergency point operation with sealing arrangements & counters.

(s) SM’s key is to be provided to lock the panel to prevent unauthorized

operation

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 Basic Requirements of Metal to Carbon Relay Interlocking

Control Panel:
(a) All signals are provided with rotary type switches or buttons nearer to the
geographical location with indications.

(b) All points are provided with 2 position. / 3 position. switches for PI & RRI
respectively with indications for Normal (Yellow), Reverse (Green), Locked
(Red), Free (White)

(c)Track circuits as per yard, demarcation are provided with different colours
and occupied/failed indication is given in RED.

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 Basic Requirements of Metal to Carbon Relay Interlocking

(d) Controls for Sidings, Level Crossings, Crank Handles are also provided with
button/switches & indications.

(e)When route is set and locked, white strip light indications will appear in the
route and will be extinguished on arrival of train or on cancellation.

(f) Controls for emergency signal and route cancellation, emergency point
operations with counters are provided.

(g)SM’s key will be provided to lock the panel to prevent unauthorized

operation.

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 Basic Requirements of Metal to Carbon Relay Interlocking

Note :
In a control panel, there is no physical interlocking between various switches
and buttons like Mechanical lever frame, but the associated controlling relays
will not pick up unless all the conditions required are favourable.

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 Basic Requirements of Metal to Carbon Relay Interlocking -
Panels
(a) Conventional Panel (Single plate - Non Domino Type) :
• In conventional type, only a single large plate of required size is taken and
holes/slots are cut to provide switches, buttons, indications, counters, keys
etc.
(b) Domino Type Panel:
• In Domino type, the entire panel is made up of assembling together small
rectangular plates/boxes of sizes 63mmx38mm and 54mmx34mm on a
frame.
• The buttons, switches & indications, etc are fitted to the dominos and its
bases.
• Wiring is also terminated into male/female multiple sockets for easy
removal/ assembly.
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 Single Plate – Non Domino type

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 Domino Type Panel

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 Domino Type Panel

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 Domino Type Panel

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 Domino Type Panel

6 1
0
15

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 Advantages of Domino Type panels

(i) Miniature push button operation for each function.

(ii) All buttons are Self-restoring type.
(iii) Route gets released as the train clears the route, no extra operation is
required.
(iv) Operating panel becomes compact & neat though yard is very big.
(v) Easy to make deletion and addition on the operating panel during yard
modification.
(vi) As Domino has got spring loaded silver tipped contacts, the lamp and
button contact failures are less comparatively.
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 Control and Indication Panel

Note:
If required, depending upon the size of the installation the control panel can be
separated. A separate indication panel at a suitable place and an operating
panel with SM’s key, button & switches can be provided at a suitable place.

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 INDICATIONS ON PANEL :

INDICATIONS ON PANEL :
1.Track circuits indications
2.Point Indications
3.Signal Indications
4.Miscellaneous Indications

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 INDICATIONS ON PANEL :

Track circuits indications:

Track clear - No indication

Track clear, Route set and Locked - White
Track Occupation / failure - Red

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 INDICATIONS ON PANEL :

Track clear – No indication

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 INDICATIONS ON PANEL :

Track clear, Route set and Locked - White

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 INDICATIONS ON PANEL :

Track Occupation / failure - Red

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 INDICATIONS ON PANEL :

Points indications:
Method I : Near the point knob/switch
Normal & Locked - Yellow
Reverse & Locked - Green
Locked in Route - Red
Point Free - Yellow / White
Siding point Normal and key IN - Yellow
Siding control key out - No light

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 INDICATIONS ON PANEL :
Normal Free Reverse

0
2 POSITION KNOBS

3 POSITION
KNOB

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 INDICATIONS ON PANEL :

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 INDICATIONS ON PANEL :

Points indications -Method II :

• White strip light indication of Normal/Reverse may also be shown on the
panel near the point zone.
• During the operation of a point, the light/strip light for the intended position
will flash till points are correctly set and locked.
• When no signal is taken off and route is not set & locked over a point, the free
indication if provided will appear.
• Free indication will extinguish when the point is locked in a route or
concerned point zone track circuit failed or SM’s key is removed.

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 INDICATIONS ON PANEL :

Points indications -Method II :

• White strip indication of Normal/Reverse may also be shown on the panel
near the point zone.
Point Normal – Track free Point Reverse- Track free

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 INDICATIONS ON PANEL :

Points indications - Method II :

• White strip indication of Normal/Reverse may also be shown on the panel
near the point zone.
Point Normal operation Point Reverse operation

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 INDICATIONS ON PANEL :

Points indications-Method II :
• Free indication will extinguish when the point is locked in a route or
concerned point zone track circuit failed or SM’s key is removed
Point Locking Indication Point Reverse –Track occupied

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 INDICATIONS ON PANEL :
Point Normal – Track free Point Reverse- Track free

Point Locking Indication Point Reverse –Track occupied

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 INDICATIONS ON PANEL :

Point Normal- Track Occupied Point No.107 Reverse & 108 Normal

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 INDICATIONS ON PANEL :

Stop Signal ‘ON’ - Red

‘OFF’ -Yellow/green/double yellow
Route ‘ON’ - No indication
‘OFF’ - White strip
Permissive ‘ON’ - Yellow
(Distant) ‘OFF’ - Green/Double yellow
‘Calling ’ON’ Signal ‘ON’ - No indication

‘OFF’ -Miniature yellow indication

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 INDICATIONS ON PANEL :

Shunt Signal On a separate post

ON - 2 White lights Horizontal
OFF - 2 White lights Diagonal / slanting
(One light common in both)
On a post below a stop signal
‘ON’ - No indication
‘OFF’ - 2 White lights Diagonal / slanting

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 INDICATIONS ON PANEL :

Stop Signal (Starter) ‘ON ‘ Position Calling-on signal ON position

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 INDICATIONS ON PANEL :

Stop Signal (Home) ‘OFF’ Aspect` Calling-on ‘OFF’ Aspect

Route Indicator

Shunt signal ‘ON’ Aspect

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 INDICATIONS ON PANEL :

Permissive Signal ‘ON ‘Aspect Permissive Signal ‘OFF ‘Aspect

Permissive Signal ‘OFF ‘Aspect

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 INDICATIONS ON PANEL :

LC Gate open LC gate closed

SM Key IN SM Key OUT

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 INDICATIONS ON PANEL :

Miscellaneous indication

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 Colour of Button switch used on the Panel

Colour Colour
S.No Description Type
(As per SEM) (Practice)
1 Signal (GN) Button / switch Red Red
2 Calling 'on' signal Button / Switch Red with white Red with
(GN) dot white dot
3 Common calling Button Red Red
'on’initiation(COGGN)
4 Shunt signal (GN) Button / switch Yellow Yellow
5 Route(exit/through) (UN) Button White Grey
6 Route(alternate overlap) Button White with black Grey
(UN) dot
7 Route(alternate route) (UN) Button Grey Grey
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 Colour of Button switch used on the Panel

S.No Description Type Colour Colour

(As per SEM) (Practice)
8 Point (WN) Button / switch Black Blue/ Black

9 Common point-normal Button Black with red Blue

NWN / WWN dot
10 Common point-reverse Button Black with red Blue
RWN / WWR dot
11 Crank handle (CHN) Button Blue Blue
12 Siding control (ZNN) Button / switch Blue/Black Black/ Blue

13 Emer. Sig. Canc. (EGGN) Button Red Red

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 Colour of Button switch used on the Panel

S.No Description Type Colour Colour

(as per SEM) (practice)
14 Emergency Full route Button Grey Grey
cancellation (EUUYN)
15 Emergency Point operation(EWN) Button Black with Red Blue
dot
16 Slot (trans) (YYN) Button Green Grey/
Green
17 Slot (receive) (YRN) Button Green Grey/
Green
18 Power ‘ Ack ' Button Red Red
19 Point Ind. Failure ack. ( WXYN) Button Grey Grey
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 Colour of Button switch used on the Panel

S.No Description Type Colour Colour

(as per S.E.M.) (practice)
20 Sig lamp. Failure ack. ( GXYN) Button Grey Grey

21 Button stuck up ack. (ACKNR) Button Grey Grey

22 Level crossing gate control Buttons Green / Brown Green/ Brown

(LXN/LXYN/LXYRN)

23 S.M.'s key 2 Pos. Metallic white Metallic white

Switch

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 Indication Colours of Points, Signals etc. on Panel

S.No Description Aspect/Condition Colour

1 Signal ON Red (distant - yellow)
2 OFF Yellow/green/Double yellow
3 Route White strip
4 C 'on' Signal ON No light
5 OFF Miniature yellow
6 Shunt Signal ON 2 Hoz.White Lights
7 (separate) OFF 2 Cross White Lights
8 Shunt Signal ON No Light
9 (combined) OFF 2 Cross White Lights

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 Indication Colours of Points, Signals etc. on Panel

S.No. Description Aspect/Condition Colour

10 Point Normal Yellow / White strip
11 Reverse Green / White strip
12 Locked / Free Red / White
13 Crank Handle IN Green
14 OUT Red
15 Free White
16 Track Circuit Occupied Red
17 Clear (When Signal is 'ON') No light
18 Clear (When Signal is 'OFF') White strip

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 Indication Colours of Points, Signals etc. on Panel

S.No. Description Aspect/Condition Colour

19 L.C.gate Open Red
20 Close Yellow / Green
21 Slot Grant / Receive Yellow
22 Power ‘Ack’ Failed Red
23 Signal lamp failure Lamp fused Yellow
24 Point ind. failure Ind. Failed Yellow
25 Button stuck up Button Stuck Up Yellow

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 Name of the Button Nomenclature
Signal GN
Route UN
Calling On Signal COGGN
Point WN
Common point-normal NWWN
Common point-reverse RWWN
Crank handle CHN
Siding control KLN
Emer. Sig. Cancellation EGGN

LC gate control LXN

Emer. Point operation EWN
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 Name of the Button Nomenclature

LC gate control LXN

Emer. Point operation EWN
Slot (trans) YYN
Slot (release) YRN
Emer. Full route cancellation EUUYN

Emer. Sub route cancellation EUYN

Point ind. Failure ack WXYN

Sig lamp. Failure ack GXYN
Button stuck up ack. ACKNR
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 RELAY INTERLOCKING
(Metal –Carbon Relays)
Sequence of Operations on Panel

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 Sequence of Operations on Panel

Various stages of operation

• setting the route,
• Locking and clearing a signal &
• release the route on arrival of train and
• other operations performed on the panel

The sequence of operations slightly varies between PI & RRI.

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 Sequence of Operations on Panel

Setting of Route and Clearing a signal

Non Route Setting Type (Panel Interlocking)
(a) Manual Operation of Points:
•The route is set by operating individually the points in the route, overlap and
in isolation.
•When the points are correctly set and locked in the required position then the
concerned indication NWKR/RWKR will appear on the panel.
•It is to note that before a point is operated, all the condition like SM key `IN’,
point is free from any route, crank handle `IN’ and track is clear, must be
fulfilled.

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 Sequence of Operations on Panel

Setting of Route and Clearing a signal

Non Route Setting Type (Panel Interlocking)
(b) Signal Knob Reversed for Clearing the Signal:
After ensuring that all the required points are correctly set and locked and
indications are available, the concerned signal switch is turned to ‘Reverse’ (R)
and RR is energized proving conflicting RRs in drop condition.

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 Sequence of Operations on Panel

Setting of Route and Clearing a signal

Non Route Setting Type (Panel Interlocking)
(c) UCR picking up (Route checking): The concerned UCR relay picks up after
ensuring the route which was set manually is correct and the conflicting ASRs
(pick up)/UCRs(drop) are in favourable condition.

(d) ASR/ALSR Dropping (Route Locking): As and when the route checking relay
UCR is energised, the concerned (signal) ASR along with overlap controlling
relays OVSR’s will drop and there by, all the points in the route, overlap and
isolation are locked. The ASR dropping ensures WLRs to remain in drop
condition and thereby locks the points.
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 Sequence of Operations on Panel

Setting of Route and Clearing a signal

Non Route Setting Type (Panel Interlocking)
(e) HR Pick up (Signal clearing): UCR picks up , ASR drops and the route is
locked, then the signal is taken off, provided all other conditions required for
clearing of a signal are fulfilled . The signal ‘OFF’ indications will appear on
panel.

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 NON ROUTE SETTING TYPE /
PANEL INTERLOCKING

SMCR

Manual
Operation of Points
NWKRs / RWKRs

Schematic Diagram for Signal Knob R Conflicting

Clearing a Signal in PI RR RR

Conflicting
UCR UCR ASR
OVSR

ASR Route Locked

Point WLR's

HR

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 Sequence of Operations on Panel

Setting of Route and Clearing a signal

Route Setting Type / Route Relay Interlocking
In this system, setting of route, Locking of Route and clearance of a signal are
done simultaneously at the same time.
Route Selection : When the signal switch/Button and Route button are
operated simultaneously, concerned route selection relay, NRR picks up. Every
signal will have as many NRRs as that of number of routes.

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 Sequence of Operations on Panel

Setting of Route and Clearing a signal

Route Setting Type / Route Relay Interlocking
Route Setting: The picked up NRR decides the point position for a given signal
route. The picked up NRR contacts are used in the required point control
circuits, to operate them to correct position for that signal route, in case those
points are not already in favourable condition.

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 Sequence of Operations on Panel

Setting of Route and Clearing a signal

Route Setting Type / Route Relay Interlocking
Route Checking :
Once the required points are correctly set and locked and concerned point
indications (NWKR/RWKRs) Relays are picked up, the route checking relay UCR
will pick up.
Route Locking :
Immediately ASR/ALSR along with overlap controlling relays OVSRs and TLSRs/
TRSRs (depending upon the direction of movement of train) will drop and there
by all points in the route, overlap and isolation are locked ( Route locked).

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 Sequence of Operations on Panel

Signal Clearing :
Then the signal is taken ‘off’ immediately provided all other conditions for
clearing a signal are available.

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 ROUTE SETTING TYPE /
ROUTE RELAY INTERLOCKING

SMCR

Route
Signal Knob R (OR)
Button
Signal Button Pressed Pressed

Signal Route LR or Conflicting LR's

Schematic Diagram for NRR
NRR
or

Clearing a Signal in RRI

Auto Operation of Points
NWKRs / RWKRs

Conf UCR
UCR ASR OVSR
TLSR/TRSR

Route Locked
ASR
Point WLR's

HR

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 Panel Interlocking Route Relay Interlocking
NON ROUTE SETTING TYPE / ROUTE SETTING TYPE /
PANEL INTERLOCKING ROUTE RELAY INTERLOCKING

SMCR SMCR

Manual Route
Signal Knob R (OR)
Operation of Points Button
NWKRs / RWKRs Signal Button Pressed Pressed

Signal Knob R Conflicting Signal Route LR or Conflicting LR's

or
RR RR NRR
NRR

Conflicting
UCR UCR ASR Auto Operation of Points
OVSR NWKRs / RWKRs

Conf UCR
ASR Route Locked ASR OVSR
Point WLR's UCR
TLSR/TRSR

HR Route Locked
ASR
Point WLR's

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 Manual operation of points in Route setting Type

• In RRIs the points are required to be operated manually for points testing and
automatically through route initiation.
• In case of knobs, 3 position point knobs are provided which will have N-C-R
positions.
• Normally the switch will be in ‘centre’ position for automatic operation and for
manual operation it is to be operated as required and brought back to centre
position for subsequent auto operation.

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 Manual operation of points in Route setting Type

• Where buttons are provided, the concerned point button and common point
button (N or R) are pressed simultaneously to set the point to the required
side.
• As buttons are self restoring type, relevant button relay drop contacts are
used for auto operation of points through route initiation.

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 Manual operation of points in Route setting Type

2 POSITION KNOB - PI

3 POSITION KNOB - RRI

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 Manual operation of points in Route setting Type

Manual operation of points in RRI

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 Releasing of Route for a Signal

• On passage of train, the signal will be automatically replaced to `ON’

• The train on entering and clearing the route, the track circuits will operate
sequentially and the sequential route release relays (UYRs) will pick up.
• When the train completely clears the last back lock track circuit and signal
knob normalised, then the concerned ASR picks up and the route gets
released.
• The ASR picks up and the sequential route release relays will drop.

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 Releasing of Route for a Signal

• Similarly, for an RRI with SRR, TLSR/TRSR’s will also pick up after ASR picks up
and remain in up.
• The OVSR’s will pick up after 120 seconds for a stopping train OR after passage
of train beyond the overlap with starter taken ‘OFF’.

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 Cancellation of Signal and Releasing of Route (Points)

A Signal can be cancelled by simply turning the Signal knob to normal position
or by pressing signal button along with Emergency signal cancellation button.
But the route releasing depends upon approach locking provided.
Case 1:
Where Sufficient length of track circuit is provided (in approach) in rear of a
signal, the route can be released with out time delay, when the approach track
is clear and with time delay when Approach Track is occupied.

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 Cancellation of Signal and Releasing of Route (Points)

Case 2 :
• Where sufficient length of track circuit is not provided then the route releasing
is possible with time delay only irrespective of position of train.
• The length of approach track depends upon sectional permissible speed, the
type of signalling etc. Counters are provided for registering all emergency
operations.

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 RELAY INTERLOCKING
(Metal –Carbon Relays)
SIGNALLING PLAN – CONTROL TABLE

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 Signalling Plan

• On receiving the approved Engineering plan, a signalling plan is prepared by

Drawing office.

• The prepared signalling plan is sent to traffic department (COM) and

Sr.DSTE/Division for their comments about the signalling plan.

• If required alterations are done in the signalling plan as per the comments
received.

• Then the signal plan is put up for approval by CSTE for executing works.

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 Signal Numbering pattern Practice - 1

(a) Running signals - DN direction – ODD Numbers 1,3,5,7

(b) Running signals - up direction – Even Numbers 2,4,6,8.
(c) Subsidiary signal like shunt signals etc.- DN direction - ODD number 41,43 ….
(d) Subsidiary signal like shunt signals etc.- Up direction - Even number 42, 44….
(e) Points - 101, 102, 103
(f) Siding control – 201, 202, 203
(g) LC gate control – 301,302, …

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 Signal Numbering pattern Practice - 2

• Running signal pertaining to one direction with LHS to RHS of operator facing
towards the panel – Home signal, main line starter, loop line starter, Advance
starter and L.C. gate, shunt signal, Points at one End , points at other end ,
shunt signal , L.C. gate, Running signals-Advance starter, L/L starter, M/L
Starter and Home signal.

• Note: some railways adopt mechanical numbering pattern, where signals,

points etc are numbered serially starting from 1,2,3 as that of mechanical
lever frame.

02-09-2022 S12 British Interlocking Version 1.0

 Signal Numbering pattern Practice - 2

LH RH

Home, M/L Str., L/L Str., Adv Str. Shunt sig

LH Side points, Sdg. Pt, RH Side Points ,LC Gate

Shunt sig , Adv Str., L/L Str., M/L Str., Home

02-09-2022 S12 British Interlocking Version 1.0
 RELAY INTERLOCKING
(Metal –Carbon Relays)

ROUTE SETTING TYPE RELAY INTERLOCKING (RRI)

02-09-2022 S12 British Interlocking Version 1.0

 Signal Interlocking Panel

STATION 'B'
(EMERGENCY)
SPARES NOs: 2.5.7.8.9.14. (POINTS:13.18) (POINT:11.20.) (POINTS:12.19)
L.C.GATE 16.17.24.29.
PANEL (30 FUNCTIONS)

UP LINE UP LINE CH1 CH2

STATION 'B' - STATION 'C' STATION 'A' - STATION 'B'

BOXES OF BPAC FOR BOXES OF BPAC FOR
PREPARATORY RESETTING PREPARATORY RESETTING
DN.LINE DN.LINE

L STATION 'A' - STATION 'B'

STATION 'B' - STATION 'C'
C GL

GATE CONTROL: 22
1 KM 180 Mts (Min.) 4
1 KM AT Km.8/9-10
(Min.)
13A
T 13 DN. COMMON LOOP UP 18 18AT `SPL'CLASS LC NO.4
1 D(2) 1 D(1) CLAT CLT
6
1A 1 CLAT CLBT CLCT

B
26 3 3/4T
DN BPAC 11 13 20
1BT 1AT 1T 11AT DMAT DMBT DMCT 20AT 3/4T
DMT
DN. MAIN 13BT DN. MAIN 18BT 6T DN.MAIN
18 DN.BPAC
10 23 21 STATION 'A'
UP BPAC 26-28T
STATION 'C' 26-28T 12BT UP. MAIN 19T UP MAIN
UMT
UP. MAIN UMCT UMBT UMAT 20BT 30T
25T 11 11BT 12 28 19 20 UP BPAC 30AT
SB
19
B

25 ULCT ULBT ULAT 30 30A 30 D(1) 30 D(2)

ULAT ULT
12AT UP. LOOP
12
15 KL
BS
27 SIDING
LEVER G.F 180 Mts 1 KM 1 KM
(Min.) (Min.)
 CONTROL TABLE

COLUMN NO. CONTENTS OF THE COLUMN

1 SERIAL NUMBER
2 SIGNAL NUMBER
3 ROUTE ( DESTINATION )
4 OPERATE SIGNAL BUTTON
BUTTONS
5 ROUTE BUTTON
6 NORMAL
ROUTE
7 REVERSE
8 LOCKS/ NORMAL
DETECTS ISOLATION
9 POINTS REVERSE
10 NORMAL
OVERLAP
11 REVERSE

02-09-2022 S12 British Interlocking Version 1.0

 CONTROL TABLE
COLUMN NO. CONTENTS OF THE COLUMN
12 ROUTE
CONTROLLED BY
13 TRACK CIRCUITS OVERLAP
14 FOULING
15 OTHER CONTROLS CH, LXC,
IF ANY
SDG SLOT, etc.
16 APPROACH /DEAD APPROACH
LOCKED BY TRACK CIRCUITS
17 BACK LOCKED BY TRACK CIRCUITS
18 LOCK ROUTES
19 AHEAD SIGNAL ASPECT
20 REMARKS

02-09-2022 S12 British Interlocking Version 1.0

02-09-2022 S12 British Interlocking Version 1.0 86
02-09-2022 S12 British Interlocking Version 1.0 87
02-09-2022 S12 British Interlocking Version 1.0 88
02-09-2022 S12 British Interlocking Version 1.0 89
02-09-2022 S12 British Interlocking Version 1.0 90
02-09-2022 S12 British Interlocking Version 1.0 91
 POINT CONTROL TABLE

S NO POINT TRACK LOCKED BY SIGNAL REMARK

LOCKED BY
1 11 11AT,11BT 1,1A,10,23,26,27,28,(30 W19R 12R) , CH2
(30 W19N 20N) (30 W13R 20R)
2 12 12AT,12BT (10 W11N),26,27,28,(30W 20N) CH3
3 13 13AT,13BT 1,1A,(10 W11R),23,26,(30 W20R) CH1
5 18 18AT,18BT 1,3,4,21,(30,30A W20R) CH1
6 19 19T 30,30A CH3
7 20 20AT,20BT (1 W13N OR18R),3,4,6,21,30,30A CH2
8 15 KL - (30 W19R 12N), (30 W19R 12R), -
(30A W19R),27,(SH-10 W12R)

02-09-2022 S12 British Interlocking Version 1.0 92

 RELAY INTERLOCKING
(Metal –Carbon Relays)
Nomenclature of Relays and Circuits of
ROUTE SETTING TYPE RELAY INTERLOCKING (Knob type)
02-09-2022 S12 British Interlocking Version 1.0 93
 Abbreviations used in “Relay Interlocking” (British)
A Approach, Automatic
B Back, Block, Positive
C Checking, Proving
D Clear (Green)
E Lamp
F Fuse, Front
G Signal, Gate, Group
H Home, Yellow, Caution
I Indication
J Time Delay
K Detection, Indication
L Lock, Left
M Main, Manual, Marker
02-09-2022 S12 British Interlocking Version 1.0 94
 Abbreviations used in “Relay Interlocking” (British)
N Normal, Button, Negative
O Overlap
P Proving, Repeater, Primary
Q Q style
R Reverse, Right, Red
S Slow, Stick
T Track, Time
U Route
V Vital, voltage
W Point
X Buzzer
Y Slot, Yellow
Z Special, Zone
02-09-2022 S12 British Interlocking Version 1.0 95
 Relays used in “ROUTE RELAY INTERLOCKING”

S.No Nomenclature Description Remark /Function

1 SMR/SMCR Station Master’s (control) Relay Authorised Operation

2 TSR Track Stick Relay One Signal - One Train

3 RR Signal Knob / Switch Reverse Relay For taking “OFF” Signal in PI
4 UCR Route Checking Relay Ensures Correct Route Set

5 Co UCR Calling ‘ON‘ Signal Route Checking Ensures Correct Route Set For
Relay calling ‘ON’
6 HR/HHR/DR Signal control Relays for Yellow / Allows Signal to take ‘OFF’
Double Yellow/ Green

02-09-2022 S12 British Interlocking Version 1.0

 Relays used in “ROUTE RELAY INTERLOCKING”

S.No Nomenclature Description Remark /Function

7 UHR/UR/UGR Signal control Relays for Route Allows Route Lamps to burn
8 HPR/HHPR/DPR Repeater relays of Signal control Used in Locations
Relays
9 RECR/HECR/ Signal Lamp proving Relays for When picked up, Proves Lamp
DECR/UECR Red/Yellow/ Green /Route etc. is burning
10 ASR/ALSR Approach Lock Stick Relay When pick up , Route free
When drop , Route locked
11 OVSR Over lap Stick Relay When drop , locks points in
Overlap

02-09-2022 S12 British Interlocking Version 1.0

 Relays used in “ROUTE RELAY INTERLOCKING”

S.No Nomenclature Description Remark /Function

12 UYR1, 2, 3... Sequential Route Release Relays Proves directional arrival of a train
in the set route.
13 NWR / RWR Normal / Reverse point operating Final Relay for point operation
Relay
14 NWKR Normal Point indication Relay Picks up when point set and
locked in Normal
15 RWKR Reverse point indication Relay Picks up when point set and
locked in Reverse
16 NWSR / RWSR Normal / Reverse point Indication stick relay
indication stick Relay

02-09-2022 S12 British Interlocking Version 1.0

 Relays used in “ROUTE RELAY INTERLOCKING”

S.No Nomenclature Description Remark /Function

17 NCR / RCR Point Normal / Reverse Relay Switch control relays

18 WLR Point Lock Relay Point Free

19 WNR / WRR Point Normal / Reverse control First Relay to pick up in point control
Relay cct.
20 WJR Point Time control Relay Controls DC 110V to point motor for
a fixed time.

21 WXR Point Special Relay Controls DC 110V to point motor

02-09-2022 S12 British Interlocking Version 1.0

 Relays used in “ROUTE RELAY INTERLOCKING”

S.No Nomenclature Description Remark /Function

22 CHFR Crank Handle Free Relay

23 CHRR Crank handle Control Reverse Relay

24 CHLR Crank Handle Proving Relay

25 CH (IN) PR Crank Handle (IN) Proving relay

26 CHYR Crank Handle Slot Relay

02-09-2022 S12 British Interlocking Version 1.0

 Relays used in “ROUTE RELAY INTERLOCKING”

S.No Nomenclature Description Remark /Function

27 JSR Time Stick Relay Pick up with HOT contact

28 JR Timer Relay Pick up with Cold contact

make
29 JSLR Timer Stick lock Relay Initiates Timers

30 NJPR Normal Timer (out) proving Relay Pick up after 120 sec.

31 RJPR Reverse Time proving Relay Proves JSLR‘s and NJPR’s are
dropped

02-09-2022 S12 British Interlocking Version 1.0

 Relays used in “ROUTE RELAY INTERLOCKING”

S.No Nomenclature Description Remark /Function

32 GXJR Signal Lamp Proving Relay All Signals Burning

33 WXJR Point Indication Proving Relay Point Indication OK

34 GXYNR sig amp Failure Ack. Button Relay Buzzer Mute

35 GECR Signal Aspect Checking / Proving Signal Not Blank

Relay
36 MECR Signal lamp Main Filament Indicates Main Filament Burning
Proving Relay when in picked up condition

02-09-2022 S12 British Interlocking Version 1.0

 Relays used in “ROUTE RELAY INTERLOCKING”

S.No Nomenclature Description Remark /Function

37 EUUYNR Emergency Route cancellation To release Route
button Relay
38 LVR Low voltage Relay Drops for low AC 230 voltage

39 SLR Power ‘ON’ Ack. Relay -

40 Sdg. NPR Siding Normal Proving relay

41 LXPR Level Crossing Proving Relay

02-09-2022 S12 British Interlocking Version 1.0

 S.No. SYMBOL DESCRIPTION
Symbols used in “Relay
1 FUSE
Interlocking” (British)
B
2 DC POSITIVE SUPPLY

N
3 D C NEGATIVE SUPPLY

BX AC LINE SUPPLY
4

NX
AC NEUTRAL SUPPLY
5

6 DC FLASHER SUPPLY

R1 R2
7 DC NEUTRAL RELAY COIL (Q STYLE RELAY)

IP

R1
TIMER
8 OP (XX SEC) ELECTRONIC TIMER
A1

9 N R
POLARISED RELAY

10 SLOW TO RELEASE RELAY COIL

11 SLOW TO PICKUP RELAY COIL

R1 R3
12 R2 R4 DOUBLE COIL RELAYRELAY (TWIN RELAYS)

13 AC IMMUNISED RELAY COIL

R1 R2
LATCH RELAY COIL
14 R3 R4

15 FRONT CONTACT (Q STYLE RELAY)

02-09-2022 S12 British Interlocking Version 1.0
 S.No. SYMBOL DESCRIPTION Symbols used in “Relay
16 BACK CONTACT (Q STYLE RELAY)
Interlocking” (British)
17 TIME ELEMENT RELAY FRONT CONTACT
(ENERGISED CONDITION)

18 TIME ELEMENT RELAY BACK CONTACT

(DE-ENERGISED CONDITION)

FLASHER RELAY CONTACTS

19

N
2 POSITION POLAR RELAY (DEPENDANT TYPE)
20
R NORMAL/REVERSE CONTACTS

3 POSITION POLAR RELAY (INDEPENDANT TYPE)

21 N NORMAL CONTACTS (ENERGISATION ON NORMAL SIDE)

3 POSITION POLAR RELAY (INDEPENDANT TYPE)

22 R REVERSE CONTACTS (ENERGISATION ON REVERSE SIDE)

3 POSITION POLAR RELAY (INDEPENDANT TYPE)

23 D DE-ENERGISED CONTACTS

N 2 POSITION POLAR RELAY (INDEPENDANT TYPE)

24 NORMAL CONTACTS

R 2 POSITION POLAR RELAY (INDEPENDANT TYPE)

25
REVERSE CONTACTS

26 PANEL TERMINAL

27 CT RACK TERMINAL

28 N KNOB NORMAL

29 R KNOB REVERSE

PUSH BUTTON NORMALLY OPEN

30
02-09-2022 S12 British Interlocking Version 1.0
 S.No. SYMBOL DESCRIPTION
Symbols used in “Relay
Interlocking” (British)
P
31 (N.C) PUSH BUTTON NORMALLY CLOSE

32 TOGGLE SWITCH

KEY CONTACTS
33

EKT/RKT CONTACT
34

L
EKT COIL
35

RESISTOR
36

+ - CAPACITOR
37

DIODE
38

39 BUZZER
BUZZER

40 COUNTER COUNTER

NC
41 POINT MACHINE NORMAL CONTROL CONTACTS

RC
42 POINT MACHINE REVERSE CONTROL CONTACTS

43 +
POINT MACHINE NORMAL DETECTION CONTACTS

44 *
POINT MACHINE REVERSE DETECTION CONTACTS

45 POINT MACHINE CRANK HANDLE CUTOUT

02-09-2022 S12 British Interlocking Version 1.0

 Signal Interlocking Panel

243.95km
`A' CLASS L.C. NO. 97
BOARD TO READ AT KM: 243/20-22 KM:244

C
``DRIVERS TO PULL GATE CONTROL: G
UPTO SIGNAL NO.1A. IF WITH LC. NO.97
THE SAME IS AT ON.
DOWN DISTANT FOR
FOR LC AT KM 247/17-19
180m GL 3 DOWN GOODS SIGHTING BOARD
BSLB FOR LC AT KM 247/17-19
1D(1) 1B 1A 54 PASSENGER PLATFORM 62
04BT
D 8
04T 04AT ROAD 4 DOWN
C
P

P
SB 65
FP 20 50 54 2 62
DOWN C1T 1T 50T 53BT O3T O3AT ROAD 3 DOWN O3BT 65BT 2T 8T DOWN
C K L
SB SB 17
25T 53AT 53 55T O2BT O2AT ROAD 2 O2T UP MAIN 65AT 32T C32T UP
J H B
UP FP 65
55 31 A1 - WITH POINTS 63 NORMAL 63
52 BSLB 32D
63 32A 32B
O1BT O1AT ROAD 1 UP DOWN O1T
A A1 BS

C
25 55 PASSENGER PLATFORM 105 63T
100
101 N ELEC
N ELEC 102 6
27 STATION BUILDING 104 R ELEC
S
RRI CONTROL PANEL KEY `C' FROM GOODS SHED
SPL. EKT N ELEC KEY `C' FROM
103 R ELEC SPL. EKT
TOWER WAGON
SIDING

BOARD TO READ
DO NOT PROCEED
WITHOUT HAND SIGNAL

+ + + + + +

CH1 CH2 CH3 CH4 CH5 CH6

(50) (52) (53) (54.62) (55.63) (65)
KEY `Y' FROM POINTS NO. 102 OR 103.
KEY `C' IN CONTROLLED BY KNOB NO.66.
 ROUTE BUTTON PROVING RELAY CIRCUIT

• Route buttons are compulsory in “Route setting” type installations.

• Every route, alternate route and alternate overlap will have separate route
buttons designate either alphabetically or with their route / overlap name.
• When route button is pressed, the concerned route button relay ‘PR’ is picked
up provided SM’s key is in condition.

02-09-2022 S12 British Interlocking Version 1.0

 ROUTE BUTTON PROVING RELAY CIRCUIT

B24
SM`S KEY N24

R1
SMR R2
N

SMR `A'
P

R1
`A'PR R2 (NO)

`B'
P

R1
`B'PR R2 (NO)

`C'
P

R1
`C'PR R2 (NO)

`C'
P

R1
`D'PR R2 (NO)

02-09-2022 S12 British Interlocking Version 1.0

 ROUTE INITIATION RELAY (LR ) CIRCUIT

• Route initiation or Route selection relay is normally in de-energized condition.

• Every signal will have that many number of LR’s, as the number of routes that
the signal can lead to different overlaps.
• This relay is energized when the signal knob is reversed and the concerned
route button is pressed, the concerned LR picks up by proving all other
conflicting route LR’s in drop.
• Once LR pickup, it sticks through its own front contact.

02-09-2022 S12 British Interlocking Version 1.0

 ROUTE INITIATION RELAY (LR ) CIRCUIT

B24 17 17 17 LX 1B 1B 1B 1A 1A 17 6 1A 2
ALR CLR SLR RR ALR CLR DLR A1LR ALR DLR KLR CLR KLR 1A `D'PR SMR 1A N24

R1
DLR R2
R
1A
DLR SMR N24

27 31 25 1A 3
HLR HLR JUR DLR KLR 1A `C'PR

R1
CLR R2
1A
CLR

32A 32A 32B 32B 66 1A 1A 2 3 17 1A

ALR BLR ALR BLR YR CLR DLR KLR KLR DLPR A1LR 1A `A'PR

R1
ALR R2
1A
ALR

1A
ALR 1A A1
P

R1
A1LR R2 (NO)
1A
A1LR

10-08-2022 S12 British Interlocking Version 1.0

 Automatic Operation of Points

• When route initiation relay LR picks up it initiates automatic point operation.

• To take off the signal S1A to mainline , S1A signal knob turned to reverse and
concerned ‘C’ route button is pressed simultaneously there by 1A CLR picks up
and sticks through its own front contact.
• The moment LR picks up, it selects all the points required for that route and
initiates point operation by picking up of concerned WLR.
• If required point is already in required position point operation will not be
initiated and If point is not in the required position point will be initiated for
operation.
• If point requires operating to Normal WNR will be energised and for Reverse
WRR relay will be energised.

02-09-2022 S12 British Interlocking Version 1.0

 Automatic Operation of Points

B24 1A 1B 53B
SMR ASR ASR TPR CHR4
A

54 N24

R1
WLR R2
1A 1B
DLR DLR

1A 1B 54 54 54 54 54
DLR DLR 54 54 NWKR WRR WLR WLR WLR
R NC

A 54

R1 WNR R2

1A 1A 1A 1B 1B
CLR ALR A1LPR ALPR CLPR 54
N
1A 1A 1A 1B 1B 54 54 54 54
CLR ALR A1LPR ALPR CLPR 54 34 RWKR WNR WLR WLR
RC

54

R1 WRR R2

10-08-2022 S12 British Interlocking Version 1.0

 SECTIONAL ROUTE RELEARE CIRCUITS
(TLSR/TRSR)
• The entire route is divided into small Sub-route sections, according to the
point zones.
• When the signals are given for a particular route all the Sub route sections
in the route are locked, thereby the entire route is locked.
• But, the train on clearing each Sub route section of the route entered
clears the locking effecting of that Sub route thereby those points cleared by
the train can be utilized for other movements thereby increasing the flexibility
of the yard.
• The first route section is directly controlled by the concerned ASR.

02-09-2022 S12 British Interlocking Version 1.0

 SECTIONAL ROUTE RELEASE CIRCUITS
(TLSR/TRSR)
• The subsequent route sections are controlled by the TLSR/TRSR’s. For
‘Leftward movement’ i.e. from ‘RIGHT to LEFT’, “TLSR“ and for ‘Rightward
movement’ i.e., from ‘LEFT to RIGHT’, “TRSR” is used. Depending upon the
direction of signal movement, TLSR/TRSR’s are designed.
• The TLSR/TRSR’s do the same job as that of ASR and TLSR/TRSR picks up
contact is used in WLR pick up circuit.
• When the signal is given, ASR drops which in turn drops the required
TLSR/TRSR’s to achieve complete route locking.

02-09-2022 S12 British Interlocking Version 1.0

 SECTIONAL ROUTE RELEASE CIRCUITS
(TLSR/TRSR)

02-09-2022 S12 British Interlocking Version 1.0

 SECTIONAL ROUTE RELEASE CIRCUITS
(TLSR/TRSR)

02-09-2022 S12 British Interlocking Version 1.0

 SECTIONAL ROUTE RELEASE CIRCUITS
(TLSR/TRSR)

02-09-2022 S12 British Interlocking Version 1.0

 RELAY INTERLOCKING
(Metal –Carbon Relays)

ROUTE SETTING TYPE RELAY INTERLOCKING (RRI)

Complete PUSH BUTTON

02-09-2022 S12 British Interlocking Version 1.0

 ROUTE SETTING TYPE RELAY INTERLOCKING (RRI)

• As per the directions of RDSO/LKO for both PI&RRI, Switches must be

eliminated & Self-restoring type buttons shall be provided. Instead of single
plate panel, Domino type panel shall be provided. Also provision for
Automatic route setting (Entrance – Exit ) in way side stations, like RRI shall
be given.

02-09-2022 S12 British Interlocking Version 1.0 120

 Buttons Description & Colour

S.No Description Button Name Button colour

Point button nearer to the point
1 WN Blue
concerned
2 Common point group button for normal NWWN Blue
Common point group button for
3 RWWN Blue
Reverse
Emergency point operation button along
4 EWWN Blue
with ceiling locking arrangement
5 Crank handle control button CHN Blue
5 Crank handle control button CHN Blue
6 Slot Transmit button GSBN Grey
7 Slot Receive button GSRBN Grey
7/23/2020 S12 British Interlocking version 1.0
 Buttons Description & Colour

S.No Description Button Name Button colour

Emergency signal cancellation button with
8 EGGN Red
counter
Emergency route cancellation button with
9 EUUYN Grey
counter
10 Calling on initiation button COGGN Red
11 Signal lamp failure acknowledgement button GX ACKN Red
12 Point failure Acknowledgment button WX ACKN Blue
13 Button stuck-up acknowledgement button NN ACKN Grey
14 LC gate control button LXN Green
15 Siding control button KLN Grey
7/23/2020 S12 British Interlocking version 1.0
 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

Station Master’s (control)
1 SMR/SMCR Authorised Operation
Relay
2 TSR Track Stick Relay One Signal - One Train
Signal Knob / Switch Reverse For taking “OFF” Signal in
3 RR
Relay PI
Route Selection / Initiation For setting Route and
4 LR/NRR
Relay taking “OFF” Signal in RRI
5 UCR Route Checking Relay Ensures Correct Route Set
Calling ‘ON‘ Signal Route Ensures Correct Route Set
6 Co UCR
Checking Relay For calling ‘ON’
Signal control Relays for
7 HR/HHR/DR Allows Signal to take ‘OFF’
Yellow / Double Yellow/ Green
7/23/2020 S12 British Interlocking version 1.0
 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

Allows Route Lamps to
8 UHR/UR/UGR Signal control Relays for Route
burn
Repeater relays of Signal
9 HPR/HHPR/DPR Used in Locations
control Relays
RECR/HECR/ Signal Lamp proving Relays for When picked up, Proves
10
DECR/UECR Red/Yellow/Green /Route etc. Lamp is burning
When pick up , Route free
11 ASR/ALSR Approach Lock Stick Relay
When drop , Route locked
When drop , locks points
12 OVSR Overlap Stick Relay
in Overlap
Sequential Route Release Proves directional arrival
13 UYR1, 2, 3...
Relays of a train in the set route.
7/23/2020 S12 British Interlocking version 1.0
 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

Used in RRI for Sectional Route
14 TLSR Track Left Stick Relay
Release for Leftward movement
Track right Stick Used in RRI for Sectional Route
15 TRSR
Relay Release for rightward movement
Picks up when signal button is
16 GNR Signal Button Relay
pressed
Picks up when Route button is
17 UNR Route Button Relay
pressed
Picks up when point button is
18 WNR Point Button Relay
pressed
Crank Handle Button Picks up when crank handle button
19 CH1NR,CH2NR
Relays is pressed
7/23/2020 S12 British Interlocking version 1.0
 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

Siding Control Button Relay Picks up when siding control
20 Z1NR, Z2NR.
(S) button is pressed
Point common button Relay Pressed along with point
21 NWWN
(normal) button for Normal operation.
Point common Button Relay Pressed along with point
22 RWWN
(Reverse) button for Reverse operation.
All Signal Button Normal Drops when any signal
23 GNCR
Relay button is pressed
All Route button Normal Drops when any Route
24 UNCR
Relay button is pressed
All point button Normal Drops when any Point button
25 WNCR
Relay is pressed
7/23/2020 S12 British Interlocking version 1.0
 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

Drops when any panel
26 NNCR All panel Button Normal Relay
button is stick-up
27 GXJR Signal Lamp Proving Relay All Signals Burning
28 WXJR Point Indication Proving Relay Point Indication OK
29 GXYNR sig amp Failure Ack. Button Relay Buzzer Mute
Signal Aspect Checking / Proving
30 GECR Signal Not Blank
Relay
Indicates Main Filament
Signal lamp Main Filament
31 MECR Burning when in picked up
Proving Relay
condition
WLR/NWLR/ Point Lock Relay
32 Point Free
RWLR Normal/Reverser
7/23/2020 S12 British Interlocking version 1.0
 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

Point Normal / Reverse control First Relay to pick up in
33 WNR / WRR
Relay point control cct.
Controls DC 110V to point
34 WJR Point Time control Relay
motor for a fixed time.
Controls DC 110V to point
35 WXR Point Special Relay
motor
Normal / Reverse point Final Relay for point
36 NWR / RWR
operating Relay operation
Picks up when point set
37 NWKR Normal Point indication Relay
and locked in Normal
Picks up when point set
38 RWKR Reverse point indication Relay
and locked in Reverse
7/23/2020 S12 British Interlocking version 1.0
 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

Normal / Reverse point
39 NWSR / RWSR Indication stick relay
indication stick Relay
Point Normal / Reverse
40 NCR / RCR Switch control relays
Contact Relay
Emergency (Group) signal
41 EGGNR To put back signal to ”ON”
cancellation button relay
Emergency Route
42 EUUYNR To release Route
cancellation button Relay
Emergency Point Operation Point operation in case of
43 EWNR
Button Relay Track cct. Failure
Drops for low AC 230
44 LVR Low voltage Relay
voltage
7/23/2020 S12 British Interlocking version 1.0
 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

45 SLR Power ‘ON’ Ack. Relay -
46 JSR Time Stick Relay Pick up with HOT contact
Pick up with Cold contact
47 JR Timer Relay
make
48 JSLR Timer Stick lock Relay Initiates Timers
Normal Timer (out) proving
49 NJPR Pick up after 120 sec.
Relay
Proves JSLR‘s and NJPR’s
50 RJPR Reverse Time proving Relay
are dropped

7/23/2020 S12 British Interlocking version 1.0

 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

51 CHLR Crank Handle Lock Relay
52 CHNR Crank Handle Normal Relay
53 CHPR Crank Handle Proving Relay
54 CH (IN) PR Crank Handle (IN) Proving relay
55 CHYNR (T) Crank Handle slot Relay (Trans)
56 CHYRR (R) Crank Handle slot Relay (Receive)
57 Sdg. NPR Siding Normal Proving relay
58 LXPR Level Crossing Proving Relay
59 LXNR Level Crossing Normal Relay

7/23/2020 S12 British Interlocking version 1.0

 Relays used in “Route Relay Interlocking”

S.No Nomenclature Description Remark /Function

Level Crossing Key ‘IN’
60 LX(IN) PR/LXCR Used at Location
Proving Relay
Auto setting starting relay –
61 ASIWR Auto set point Relay – one
for chain operation
Auto set point Relay – Auto setting starting relay –
62 AS2WR
Two for chain operation
Auto chain point control Maintain the time 3 sec. Time
63 WWR
Relay gap between points
When picks up, confirms that
Auto point operation final the chain operation command
64 WWFR
normal Relay is sent to all points and feed to
chain operation is seized
7/23/2020 S12 British Interlocking version 1.0
 Signal Interlocking Panel

STATION 'B'
(EMERGENCY)
SPARES NOs: 2.5.7.8.9.14. (POINTS:13.18) (POINT:11.20.) (POINTS:12.19)
L.C.GATE 16.17.24.29.
PANEL (30 FUNCTIONS)

UP LINE UP LINE CH1 CH2

STATION 'B' - STATION 'C' STATION 'A' - STATION 'B'

BOXES OF BPAC FOR BOXES OF BPAC FOR
PREPARATORY RESETTING PREPARATORY RESETTING
DN.LINE DN.LINE

L STATION 'A' - STATION 'B'

STATION 'B' - STATION 'C'
C GL

GATE CONTROL: 22
1 KM 180 Mts (Min.) 4
1 KM AT Km.8/9-10
(Min.)
13A
T 13 DN. COMMON LOOP UP 18 18AT `SPL'CLASS LC NO.4
1 D(2) 1 D(1) CLAT CLT
6
1A 1 CLAT CLBT CLCT

B
26 3 3/4T
DN BPAC 11 13 20
1BT 1AT 1T 11AT DMAT DMBT DMCT 20AT 3/4T
DMT
DN. MAIN 13BT DN. MAIN 18BT 6T DN.MAIN
18 DN.BPAC
10 23 21 STATION 'A'
UP BPAC 26-28T
STATION 'C' 26-28T 12BT UP. MAIN 19T UP MAIN
UMT
UP. MAIN UMCT UMBT UMAT 20BT 30T
25T 11 11BT 12 28 19 20 UP BPAC 30AT
SB
19
B

25 ULCT ULBT ULAT 30 30A 30 D(1) 30 D(2)

ULAT ULT
12AT UP. LOOP
12
15 KL
BS
27 SIDING
LEVER G.F 180 Mts 1 KM 1 KM
(Min.) (Min.)
 SMR/SMCR CIRCUIT

• This relay is energized when the SM’s panel key is `IN’ and turned to Normal.
• The Energisation of SMCR/SMR relay provides authorized operation of all the
functions on the panel.
• When SM’s key is turned to reverse and taken out from panel by SM, prevents
un-authorized operation and locks the panel in the last operated position.

02-09-2022 S12 British Interlocking Version 1.0

 SMR/SMCR CIRCUIT
B24 SM'S KEY N24
IN IN
N R1
SMR R2
N

SMR

R1
SMPR1 R2

R1
SMPR2 R2

R1
SMPR3 R2

SMR

R1
SMPR4 R2

SMPR5
02-09-2022 S12 British Interlocking Version 1.0
 Signal Button Relay (GNR)

1.The signal button relay GNR is normally a de-energised relay.

2.When a signal button (GN) is pressed ,the signal button relay (GNR)
concerned picks up by proving the following conditions :
a) No other signal button (GN) is pressed i.e. No other GNR relay is in
energized condition.
b) No point button (WN) is pressed i.e. All point button normal relay is in
energized condition (WNCR).
3.In GNR &EGGNR circuits, SMR is not proved, to facilitate to throw the signal
to danger in case of emergency, though the panel is in locked condition.

7/23/2020 S12 British Interlocking version 1.0

 Signal Button Relay (GNR)

S1 S1 GNR CIRCUIT
GN S3 S4 S6 Sh 10 Sh 21 Sh 23 S 25 S 26
P GNR GNR GNR GNR GNR GNR GNR GNR

WNCR S 30 S 28 S 27
GNR GNR GNR
S1 GNR

7/23/2020 S12 British Interlocking version 1.0

 All Signal Buttons Normal Checking Relay [GNCR]

1.The relay GNCR is normally a picked up relay proving all signal button relays
are in de-energised condition (i.e. no signal button is in the pressed /stuck
up condition)

2.When a signal button is pressed, the GNR concerned is energised and drops
GNCR.

7/23/2020 S12 British Interlocking version 1.0

 All Signal Buttons Normal Checking Relay [GNCR]

S1 S1 A S3 S4 S6 Sh 10 Sh 21 Sh 23 S 25
GNR GNR GNR GNR GNR GNR GNR GNR GNR

S 30 A S 30 S 28 S 27 S 26
GNR GNR GNR GNR GNR

GNCR

7/23/2020 S12 British Interlocking version 1.0

 GNR & GNCR CIRCUIT

B24 S1 S1 S1A S3 S4 S6 Sh10 Sh10 Sh21 Sh21 Sh23

GNR1 GNR2 GNR GNR GNR GNR GNR1 GNR2 GNR1 GNR2 GNR
A

S1 S3 S4 S6 Sh10 Sh21 Sh23

GN S1 GN S3 GN S4 GN S6 GN Sh10 GN Sh21 GN Sh23
P P P P P P P
GNR1 GNR GNR GNR GNR1 GNR1 GNR
(N.O) (N.O) (N.O) (N.O) (N.O) (N.O) (N.O)

S1 Sh10 Sh21
GNR2 GNR2 GNR2

S3 S4 S6 Sh10 Sh10 Sh21 Sh21 Sh23

GNR GNR GNR GNR2 GNR1 GNR2 GNR1 GNR
B

S25 S26 S27 S28 S30 S30 S30A

GNR GNR GNR GNR GNR1 GNR2 GNR N24
A
GNCR
S25 S26 S27 S28 S30
GN S25 GN S26 GN S27 GN S28 GN S30
P P P P P
GNR GNR GNR GNR GNR1
(N.O) (N.O) (N.O) (N.O) (N.O)

S30
GNR2

S25 S26 S27 S28 S30A S30 S30

GNR GNR GNR GNR GNR GNR2 GNR1 WNCR
B

7/23/2020 S12 British Interlocking version 1.0

 GNR CIRCUIT

B24 S1 S1 S1A S3 S4 S6 Sh10 Sh10 Sh21 Sh21 Sh23

GNR1 GNR2 GNR GNR GNR GNR GNR1 GNR2 GNR1 GNR2 GNR
A

S1 S3 S4 S6 Sh10 Sh21 Sh23

GN S1 GN S3 GN S4 GN S6 GN Sh10 GN Sh21 GN Sh23
P P P P P P P
GNR1 GNR GNR GNR GNR1 GNR1 GNR
(N.O) (N.O) (N.O) (N.O) (N.O) (N.O) (N.O)

S1 Sh10 Sh21
GNR2 GNR2 GNR2

S3 S4 S6 Sh10 Sh10 Sh21 Sh21 Sh23

GNR GNR GNR GNR2 GNR1 GNR2 GNR1 GNR
B

S25 S26 S27 S28 S30 S30 S30A

GNR GNR GNR GNR GNR1 GNR2 GNR N24
A
GNCR
S25 S26 S27 S28 S30
GN S25 GN S26 GN S27 GN S28 GN S30
P P P P P
GNR GNR GNR GNR GNR1
(N.O) (N.O) (N.O) (N.O) (N.O)

S30
GNR2

S25 S26 S27 S28 S30A S30 S30

GNR GNR GNR GNR GNR GNR2 GNR1 WNCR
B

7/23/2020 S12 British Interlocking version 1.0

 GNCR CIRCUIT

B24 S1 S1 S1A S3 S4 S6 Sh10 Sh10 Sh21 Sh21 Sh23

GNR1 GNR2 GNR GNR GNR GNR GNR1 GNR2 GNR1 GNR2 GNR
A

S1 S3 S4 S6 Sh10 Sh21 Sh23

GN S1 GN S3 GN S4 GN S6 GN Sh10 GN Sh21 GN Sh23
P P P P P P P
GNR1 GNR GNR GNR GNR1 GNR1 GNR
(N.O) (N.O) (N.O) (N.O) (N.O) (N.O) (N.O)

S1 Sh10 Sh21
GNR2 GNR2 GNR2

S3 S4 S6 Sh10 Sh10 Sh21 Sh21 Sh23

GNR GNR GNR GNR2 GNR1 GNR2 GNR1 GNR
B

S25 S26 S27 S28 S30 S30 S30A

GNR GNR GNR GNR GNR1 GNR2 GNR N24
A
GNCR
S25 S26 S27 S28 S30
GN S25 GN S26 GN S27 GN S28 GN S30
P P P P P
GNR GNR GNR GNR GNR1
(N.O) (N.O) (N.O) (N.O) (N.O)

S30
GNR2

S25 S26 S27 S28 S30A S30 S30

GNR GNR GNR GNR GNR GNR2 GNR1 WNCR
B

7/23/2020 S12 British Interlocking version 1.0

 Route Button Relay (UNR)

1.The Route button relay (UNR) is normally a dropped relay.

2.Whenever the route button is pressed the route button relay (UNR) energizes
provided the following conditions are met.
All other route button relays are in the de-energised condition.
The station master’s control relay (SMR) is in the picked up condition i.e.
SM’s key in.
All point button Normal proving relay (WNCR) is in the picked up condition

7/23/2020 S12 British Interlocking version 1.0

 Route Button Relay (UNR)

DMT UNR CIRCUIT

DMT
UN UMT CLAT CLT ULAT ULT 6T
P UNR UNR UNR UNR UNR UNR

WNCR 25 T 26…28 T 3 /4 T
UNR UNR UNR
DMT UNR

7/23/2020 S12 British Interlocking version 1.0

 All Route Button Normal Checking Relay (UNCR)

• UNCR is normally an energized relay proving that no route button is in pressed condition

UNCR CIRCUIT
DMT UMT CLAT CLT ULAT ULT 6T
UNR UNR UNR UNR UNR UNR UNR

25 T 3 /4 T 26 /28 T
UNR GNR UNR
UNCR

7/23/2020 S12 British Interlocking version 1.0

 UNR & UNCR Circuit

B24 DMT UMT CLAT CLT ULAT ULT 6T

UNR UNR UNR UNR UNR UNR UNR
E

DMT UMT CLAT CLT ULAT ULT 6T

UN DMT UN UMT UN CLAT UN CLT UN ULAT UN ULT UN 6T
P P P P P P P
UNR UNR UNR UNR UNR UNR UNR
(N.O) (N.O) (N.O) (N.O) (N.O) (N.O) (N.O)

UMT CLAT CLT ULAT ULT 6T

UNR UNR UNR UNR UNR UNR
F

3/4T 26-28T 25T

UNR UNR UNR N24
E
UNCR
3/4T 26-28T 25T
UN 3/4T UN 26-28T UN 25T
P P P
UNR UNR UNR
(N.O) (N.O) (N.O)

3/4T 26-28T 25T

UNR UNR UNR SMPR WNCR
F

7/23/2020 S12 British Interlocking version 1.0

 UNR Circuit

B24 DMT UMT CLAT CLT ULAT ULT 6T

UNR UNR UNR UNR UNR UNR UNR
E

DMT UMT CLAT CLT ULAT ULT 6T

UN DMT UN UMT UN CLAT UN CLT UN ULAT UN ULT UN 6T
P P P P P P P
UNR UNR UNR UNR UNR UNR UNR
(N.O) (N.O) (N.O) (N.O) (N.O) (N.O) (N.O)

UMT CLAT CLT ULAT ULT 6T

UNR UNR UNR UNR UNR UNR
F

3/4T 26-28T 25T

UNR UNR UNR N24
E
UNCR
3/4T 26-28T 25T
UN 3/4T UN 26-28T UN 25T
P P P
UNR UNR UNR
(N.O) (N.O) (N.O)

3/4T 26-28T 25T

UNR UNR UNR SMPR WNCR
F

7/23/2020 S12 British Interlocking version 1.0

 UNCR Circuit

B24 DMT UMT CLAT CLT ULAT ULT 6T

UNR UNR UNR UNR UNR UNR UNR
E

DMT UMT CLAT CLT ULAT ULT 6T

UN DMT UN UMT UN CLAT UN CLT UN ULAT UN ULT UN 6T
P P P P P P P
UNR UNR UNR UNR UNR UNR UNR
(N.O) (N.O) (N.O) (N.O) (N.O) (N.O) (N.O)

UMT CLAT CLT ULAT ULT 6T

UNR UNR UNR UNR UNR UNR
F

3/4T 26-28T 25T

UNR UNR UNR N24
E
UNCR
3/4T 26-28T 25T
UN 3/4T UN 26-28T UN 25T
P P P
UNR UNR UNR
(N.O) (N.O) (N.O)

3/4T 26-28T 25T

UNR UNR UNR SMPR WNCR
F

7/23/2020 S12 British Interlocking version 1.0

 Point Button Relay (WNR)

1. When a point button (WN) is pressed , the point button relay (WNR)
Concerned energizes provided the following condition are met.
All other point button relays are in dropped condition i.e no other point
button is in the Pressed condition /stuck up in the pressed condition.
ALL crank handle button relays, LC gate and siding button relays in dropped
condition
All signal button normal relay GNCR, All route button normal relay (UNCR)
and station master’s relay (SMR) are in the energized condition.

7/23/2020 S12 British Interlocking version 1.0

 Point Button Relay (WNR)

11 WNR CIRCUIT
11
WN 12 13 18 19 20 GNCR UNCR SMR
P WNR WNR WNR WNR WNR
11WNR
NO

7/23/2020 S12 British Interlocking version 1.0

 All Point Button Normal Relay (WNCR)

1. All point button normal relay (WNCR) is normally a picked up relay it drops
when any one of the following button is pressed.
• Point –WN
• Crank handle-CHN
• LC Gate-LXN
• Siding-KLN
• Common point button normal-NWWN
• Common point button Reverse-RWWN
• Emergency point operation button-EWWN

7/23/2020 S12 British Interlocking version 1.0

 All Point Button Normal Relay (WNCR)

WNCR CIRCUIT
11 12 13 18 19 20
WNR WNR WNR WNR WNR WNR
WNCR

7/23/2020 S12 British Interlocking version 1.0

 WNR & WNCR CIRCUIT

B24 11 12 13 18 19 20
WNR WNR WNR WNR WNR WNR CH1NR
A

11 12 13 18 19 20
WN WN WN WN WN WN CH1N
11 12 13 18 19 20
P P P P P P P
WNR WNR WNR WNR WNR WNR CH1NR
(N.O) (N.O) (N.O) (N.O) (N.O) (N.O) (N.O)

12 13 18 19 20
WNR WNR WNR WNR WNR CH1NR
B

15 22
CH2NR CH3NR KLNR LXNR NWWNR1 NWWNR2 NWWNR3 RWWNR1 RWWNR2 RWWNR3 EWNR EWNPR N24
A
WNCR
15 22
CH2N CH3N KLN LXN
P P P 15 P 22
CH2NR CH3NR KLNR LXNR
(N.O) (N.O) (N.O) (N.O)

15 22
CH2NR CH3NR KLNR LXNR GNCR UNCR SMPR1
B

7/23/2020 S12 British Interlocking version 1.0

 WNR & WNCR CIRCUIT

B24 11 12 13 18 19 20
WNR WNR WNR WNR WNR WNR CH1NR
A

11 12 13 18 19 20
WN WN WN WN WN WN CH1N
11 12 13 18 19 20
P P P P P P P
WNR WNR WNR WNR WNR WNR CH1NR
(N.O) (N.O) (N.O) (N.O) (N.O) (N.O) (N.O)

12 13 18 19 20
WNR WNR WNR WNR WNR CH1NR
B

15 22
CH2NR CH3NR KLNR LXNR NWWNR1 NWWNR2 NWWNR3 RWWNR1 RWWNR2 RWWNR3 EWNR EWNPR N24
A
WNCR
15 22
CH2N CH3N KLN LXN
P P P 15 P 22
CH2NR CH3NR KLNR LXNR
(N.O) (N.O) (N.O) (N.O)

15 22
CH2NR CH3NR KLNR LXNR GNCR UNCR SMPR1
B

7/23/2020 S12 British Interlocking version 1.0

 WNR & WNCR CIRCUIT

B24 11 12 13 18 19 20
WNR WNR WNR WNR WNR WNR CH1NR
A

11 12 13 18 19 20
WN WN WN WN WN WN CH1N
11 12 13 18 19 20
P P P P P P P
WNR WNR WNR WNR WNR WNR CH1NR
(N.O) (N.O) (N.O) (N.O) (N.O) (N.O) (N.O)

12 13 18 19 20
WNR WNR WNR WNR WNR CH1NR
B

15 22
CH2NR CH3NR KLNR LXNR NWWNR1 NWWNR2 NWWNR3 RWWNR1 RWWNR2 RWWNR3 EWNR EWNPR N24
A
WNCR
15 22
CH2N CH3N KLN LXN
P P P 15 P 22
CH2NR CH3NR KLNR LXNR
(N.O) (N.O) (N.O) (N.O)

15 22
CH2NR CH3NR KLNR LXNR GNCR UNCR SMPR1
B

7/23/2020 S12 British Interlocking version 1.0

 AUTHOURISED OPERATION - SMR

P BOTH PRESSED & P

SIGNAL ROUTE
RELEASED SIMULTANEOUSLY
(NO) BUTTON (GN ) BUTTON (UN ) (NO)

GNR ? UNR

RR ONLY IN CASE OF HOME SIGNAL

PROVING CONFLICTING
NRR
NNRs up ( )

NNR Concerned AUTOMATIC OPERATION OF POINTS

CONCERNED TAKES PLACE REVERSE
NORMAL

PROVING CONFLICTING
UCR
ASRs / UCRs / OVSRs Point NLR Point RLR

Manual / Manual /
Point NWLR Point RWLR
Emergency Emergency
ASR
LOCKS THE ROUTE BY
NOT ALLOWING NWLRs /RWLRs NCR /RCR , PCR1 /PCR2
TO PICK UP.
TRSR/TLSR OVSR
If any
NWKR /RWKR

MAIN LINE (HOME)

& ASWRs of Required Points
OTHER SIGNALS LOOP LINE (HOME)

AS1WR
HR UGR

WWFR
DR UECR

AS2WR
HR C

Point WWR

NORMAL REVERSE
CONTROL RELAY CONTROL RELAY
NCR ? Point ASWR RCR

AT LOCATION NWR Next Point WWR RWR AT

LOCATION

WRKR WNKR
WWFR

AS2WR , All WWRs

WJR POINT TIMER RELAY

WXR

POINT OPERATION WITH

WCR WJR
HEAVY DUTY RELAY CONDENSOR FEED
M POINT MOTOR

NORMAL REVERSE

WNKR WRKR

NWR WJR WXR WCR RWR

NWKR / RWKR

02-09-2022 S12 British Interlocking Version 1.0

NWLR / RWLR
 AUTHOURISED OPERATION - SMR

P BOTH PRESSED & P

SIGNAL ROUTE
RELEASED SIMULTANEOUSLY
(NO) BUTTON (GN ) BUTTON (UN ) (NO)

GNR ? UNR

RR ONLY IN CASE OF HOME SIGNAL

PROVING CONFLICTING
NRR
NNRs up ( )

NNR Concerned AUTOMATIC OPERATION OF POINTS

CONCERNED TAKES PLACE REVERSE
NORMAL

PROVING CONFLICTING
UCR
ASRs / UCRs / OVSRs Point NLR Point RLR

Manual / Manual /
Point NWLR Point RWLR
Emergency Emergency
ASR
LOCKS THE ROUTE BY
NOT ALLOWING NWLRs /RWLRs
TO PICK UP.
TRSR/TLSR OVSR
If any

MAIN LINE (HOME)

&
OTHER SIGNALS LOOP LINE (HOME)

HR UGR

DR UECR

HR C

02-09-2022 S12 British Interlocking Version 1.0

 NRR

AUTOMATIC OPERATION OF POINTS

CONCERNED TAKES PLACE

NORMAL REVERSE

Point NLR Point RLR

Manual / Manual /
Point NWLR Point RWLR
Emergency Emergency

NCR /RCR , PCR1 /PCR2

NWKR /RWKR

ASWRs of Required Points

AS1WR

WWFR

AS2WR

Point WWR

NORMAL REVERSE
CONTROL RELAY CONTROL RELAY
NCR ? Point ASWR RCR

AT LOCATION NWR Next Point WWR RWR AT

LOCATION

WRKR WNKR
WWFR

AS2WR , All WWRs

WJR POINT TIMER RELAY

WXR

POINT OPERATION WITH

WCR WJR
HEAVY DUTY RELAY CONDENSOR FEED
M POINT MOTOR

NORMAL REVERSE

WNKR WRKR

NWR WJR WXR WCR RWR

NWKR / RWKR

NWLR / RWLR

02-09-2022 S12 British Interlocking Version 1.0

 Slot Button Relays

Slot transmission button relay (GSBNR):-

• When slot transmit button (GSBN) is pressed, slot transmit button relay
(GSBNR) is energised proving SMR↑ and GNCR ↑.

Slot receive button relay(GSRBNR):-

• When slot receive button (GSRBN) is pressed, slot receive button relay
(GSRBNR) is energised provided the station masters control relay (SMR) and all
signal button normal relay (GNCR) are in picked up condition.

02-09-2022 S12 British Interlocking Version 1.0

 Slot Button Relays

02-09-2022 S12 British Interlocking Version 1.0

 Common Point Button Relays

Normal common point button relay(NWWNR):-

• When normal common point button (NWWN) is pressed ,normal common

point button relay (NWWNR) is energized provided SMR is in picked up
condition and Reverse common point button relay (RWWNR) is in dropped
condition.

Reverse common point button relay (RWWNR):-

• When reverse common point button (RWWN) is pressed, reverse common

point button relay (RWWNR) is energized provided SMR is in picked up
condition and the normal common point button relay (NWWNR) is in dropped
condition.
02-09-2022 S12 British Interlocking Version 1.0
 Common Point Button Relays Circuit

B24 SMPR NWWN RWWNR1 RWWNR2 RWWNR3 N24

P
(NO) NWWNR1

NWWNR2

NWWNR3

RWWN NWWNR1 NWWNR2 NWWNR3

P
(NO) RWWNR1

RWWNR2

RWWNR3

02-09-2022 S12 British Interlocking Version 1.0

 CO-GGNR

Calling – ON initiation button relay (CO-GGNR) :-

• When main signal button (S1 or S30 ) and COGGN button are pressed, then
the calling-ON initiation button relay COGGNR is energized and sticks through
its own front contact which results in energization of calling ON GNR (S1A
GNR/S30A GNR)

02-09-2022 S12 British Interlocking Version 1.0

 COGGNR & CO-ON GNR Circuit
S1
B24 COGGN
GNR1 CO
P N24
(N.O) GGNR
S30
GNR1 COGGNR

S1 COGGNR
GNR1 S1A
GNR

S30
GNR1 COGGNR S30A
GNR

02-09-2022 S12 British Interlocking Version 1.0

 Emergency Signal Cancellation Button relay:

Emergency Signal Cancellation Button relay:

• The Relay EGGNR is Normally dropped relay. When emergency signal
cancellation button EGGN is pressed, EGGNR picks up. In EGGNR circuits, SMR
front contact is not proved, to facilitate to throw the signal to danger in case
of emergency, though the panel is in locked condition

B24 EGGN N24

P
(NO) EGGNR
EGGNR

EGGNPR

02-09-2022 S12 British Interlocking Version 1.0

 Button Reverse Relay –RR

• The Relay RR, is used for reception signals only .

• The RR is normally a dropped Relay.
• When S1 signal button and CLAT Route button are pressed & released
simultaneously, S1GNR and CLAT-UNR are energised there by S1-RR gets
energised provided following conditions are met (all are normally dropped
relays)
 Sequence route release relays in drop –S1UYR1 ↓
 Calling on signal (conflicting signal) RR in drop -S1A RR ↓
 Emergency signal cancellation Relay in drop –EGGNR ↓
 Calling on initiation button Relay in drop-COGGNR ↓
 Then S1 RR sticks through its own front contact by passing S1 GNR up, CLAT –
UNR up& COGGNR down.
02-09-2022 S12 British Interlocking Version 1.0
 Button Reverse Relay –RR

S1 S1A S1 S1 CLT
B24V UYR1 RR GNR1 GNR1 COGGNR UNR S1 N24V

CLAT RR
EGGNR UNR

DMT
S1 UNR
RR

S1 1A S1 S1A CLT
RR TPR GNR1 GNR1 UNR S1A

DMT RR
EGGNR S1A UNR
RR

02-09-2022 S12 British Interlocking Version 1.0

 Block Clearance Circuit:
DN
ZR3 BLOCK HANDLE
'F' K
DN TURN BLOCK
B24
ZR2 HANDLE TO TOL N24

BELL
S1A
RR
DN
• This relay (S1RR) is
DN 1 11A S1 DN
K
proved in block
ZR3 TPR TPPR1 RR ZR2 DN
ZR1
clearance circuit to
DN
ZR1 pick up ZR1, This
DN
ZR2
helps in normalization
of block, though the
1
TPR
11A
TPPR
DN
ZR1 DN reception signal fails
BLOCK BLOCK S1 DN
ZR2
to take off (HR does
HANDLE
TOL
HANDLE
TOL
GNSR ZR2 DN
ZR3
not pick up)
LB
DN
ZR3

BLOCK S1 1
HANDLE RECR TPR S1 N24

1 LC 2 GNSR
S1
GNSR

02-09-2022 S12 British Interlocking Version 1.0

 Route Normal Relay (Button Normal Relay) - NNR

1. Route normal relay is normally an energized relay and sticks through Its
own front contact by passing its own ASR relay.
2. The moment NRR picks up, it drops NNR concerned immediately.
3. The NNR picks up, when NRR drops and ASR picks up.

02-09-2022 S12 British Interlocking Version 1.0

 Route Normal Relay (Button Normal Relay) - NNR
S1 S1
B24 CLT-NRR ASPR S1-CLT N24

NNR
S1-CLT S1-CLT
NNPR NNR S1-CLT
NNPR
S1-CLAT S1
NRR ASPR S1-CLAT
NNR
S1-CLAT S1-CLAT
NNPR NNR S1-CLAT
NNPR
S1 S1
DMT-NRR ASPR S1-DMT
NNR
S1-DMT S1-DMT
NNPR NNR S1-DMT
NNPR

02-09-2022 S12 British Interlocking Version 1.0

 Track Stick Relay - TSR

• This is a one signal-one train (one movement) circuit.

• When a signal is taken off for a train and the train passes the signal, the TSR
ensures that the signal is put back to ‘ON’ immediately.
• The TSR also ensures that the signal does not Re-clear automatically, though
the signal button and route buttons are pressed once again and all other
conditions favorable.
• The stick relay is controlled by the first track circuit immediately in advance of
the signal and the normal position of the concerned signal NNR.
• The pickup contact of the relay is used in the signal control circuit (HR).

02-09-2022 S12 British Interlocking Version 1.0

 Track Stick Relay - TSR

• After the train passes the signal and the control track is occupied, TSR drops and the
signal is put back to `ON’.
• To pick up TSR again, the signal’s route is released and the dropping of controlling
relays NRR, HR and picking of NNR.
• Only after picking of TSR, the signal button and concerned route buttons are pressed
again then only to take off a signal for the next train. Thereby TSR ensures one signal
– one train feature.

02-09-2022 S12 British Interlocking Version 1.0

 Common TSR for S3,S4 and SH 21

• A combined TSR circuit can be made for signals leading to the same route
(i.e. signals conflicting in nature) and having common controlling track
circuit.
• For Home signal with `CO’ ON & Shunt on the same post or starter signals of
different lines leading towards same route or a starter signal with shunt
below it.
• It is only to reduce power consumption and economies number of TSR relays
and associated wiring.

18B 18A 20A S3 S4 SH21-DMT SH21-CLT

B24 TPPR1 TPPR TPPR NNR NNR NNR NNR S3-SH21 N24

R1 TSR R2
18
NWSR S3-SH21
TSR

02-09-2022 S12 British Interlocking Version 1.0

 TSR Circuit

18B 18A 20A S3 S4 SH21-DMT SH21-CLT

B24 TPPR1 TPPR TPPR NNR NNR NNR NNR S3-SH21 N24

R1 TSR R2
18
NWSR S3-SH21
TSR

02-09-2022 S12 British Interlocking Version 1.0

 Route Reverse Relay (Button Reverse Relay)-NRR

1. Route Reverse relay is normally a de-energized relay .

2. Its picks up, when signal button (GN) and route (UN) are pressed and
released simultaneously, proving that conflicting movements are not initiated
(NNR up).

3. Once NRR picks up, it sticks through its own front contact.

02-09-2022 S12 British Interlocking Version 1.0

 Route Reverse Relay (Button Reverse Relay)-NRR

4. When signal button S1 and route button CLAT are pressed and released
simultaneously then S1GNR and CLAT UNR picks up, there by S1-CLAT NRR
picks up and sticks through its front contact proving the following conditions
• Crank handles are in –CH1LR ↑ ,CH2LR↑
• Button reverse relay is in picked up –RR ↑ (RR is used for reception signal
only)
• Conflicting routes are not set –all NNRS up as shown in circuit diagram
• Overlap stick relays in pickup -26 OVSR ↑ , 3-OVSR↑
• Calling on signal button relay in drop-S1A GNR ↓
• Signals own route is not set –S1 ASPR↑ , 4-OVSR ↑

02-09-2022 S12 British Interlocking Version 1.0

 Route Reverse Relay (Button Reverse Relay)-NRR

NOTE:

a) The moment NRR picks up it initiates two actions

• The NNR Concerned drops.- S1CLAT NNR↓
• Initiates point chain operation

b) Route reverse relay NRR drops on two occasions

• When signal cancellation is done
• When the train travels over the set route and sequential route release
relays are picked up

02-09-2022 S12 British Interlocking Version 1.0

 Route Reverse Relay (Button Reverse Relay)-NRR

S30-CLT S30-CLAT S1 S1A-DMT S1A-CLT S4 S1-CLAT S1-CLT 26 4 S1 S1A S1 3 DMT S1-DMT S1 S1

B24 NNR NNR RR NNR N24
CH1LR CH2LR NNR NNR NNR NNR OVSPR OVSPR GNR1 GNR ASPR2 OVSR UNR NRPR RR RR

Sh 10-DMT S30A-CLT S26 Sh 23 13 18 S1-DMT

NNR NNR NNR NNR NWKPR1 NWKPR2 NRPR S1-DMT
NRR
Sh 10-CLT Sh 21-DMT Sh 21-CLT S1-DMT
NNR NNR NNR NRR S1-DMT
NRPR
S1-DMT 26 S1 S1A S1 4-OV CLT S1-CLT S1
NNR OVSR GNR1 GNR ASPR2 SPR2 UNR NRPR RR

S1-CLT
NRPR S1-CLT
NRR
S1-CLT
NRR S1-CLT
NRPR
S3 S1-CLT S1-DMT 26 3 S1 S1A S1 4 CLAT S1-CLAT S1
NNR NNR NNR OVSR OVSR GNR2 GNR ASPR2 OVSR UNR NRPR RR

S1-CLAT
NRPR S1-CLAT
NRR
S1-CLAT
NRR S1-CLAT
NRPR

02-09-2022 S12 British Interlocking Version 1.0

 Route Reverse Relay (Button Reverse Relay)-NRR

S1A-DMT S30-CLT S30-CLAT S30A-CLAT 3-OV 4-OV SH10-DMT SH21-CLT SH21 SH21 DMT SH21-DMT SH21 SH21 SH21 S3-SH21 S3-SH21
B24 CH1LR CH2LR NNR NNR NNR NNR SR SR NNR NNR GNR1 ASPR2 UNR NRPR GNR2 GNR2 GNR2 UYR1 UYR3 N24

SH21-DMT SH21-DMT
NRR SH21-DMT NRPR EGGNPR
S1-CLT S1-DMT S6 S4
NNR NNR NNR NNR NRR
SH21-DMT SH21-CLT
NRR SH21-DMT NRPR
S1A-CLT S3 S26 S1-CLAT NRPR
NNR NNR NNR NNR
SH10-CLT SH21-DMT SH21 SH21 CLT SH21-CLT SH21
NNR NNR GNR1 ASPR2 UNR NRPR GNR1

SH21-CLT
NRR SH21-CLT
NRR
SH21-CLT
NRR SH21-CLT
NRPR

02-09-2022 S12 British Interlocking Version 1.0

 Automatic Operation of Points

• When route reverse relay NRR picks up it initiates automatic point operation.
• To take off the signal S1 to common loop overlap set to mainline , S1 signal
button and CLAT route button are pressed and released simultaneously there
by S1-CLAT NRR picks up and sticks through its own front contact.
• The moment NRR picks up, it selects all the points required for that route and
initiates point operation.
• If required point is already in required position point operation will not be
initiated and If point is not in the required position point will be initiated for
operation.
• If point requires operating to Normal NLR will be energised and for Reverse
RLR relay will be energised.

02-09-2022 S12 British Interlocking Version 1.0

 Point Initiation Relay for Normal/Reverse – NLR/RLR

Point initiation relay (11NLR) picks up by proving the following conditions

• Particular signal route is initiated (S1-CLAT –NRR) ↑
• Signal route normal relay dropped (S1-CLAT-NNR) ↓
• Conflicting route settings NRRs in drop(for example SH10-DMT-NRR) ↓
• Point Normal Indication relay NWKR in drop (11NWKR ) ↓
• Point initiation relay for reverse in drop (11RLR) ↓

02-09-2022 S12 British Interlocking Version 1.0

 Point Initiation Relay for Normal/Reverse – NLR/RLR
S1-CLT S1-CLT SH10-DMT SH10-CLT SH23 S26 S30-CLAT 11 11
NRR NNR NRR NRR NRR NRR NRR NWKR RLR 11
NLR
S1-CLAT S1-CLAT
NRR NNR

S1-DMT S1-DMT
NRR NNR

S1A-CLT S1A-CLT
NRR NNR

S1A-DMT S1A-DMT
NRR NNR

SH10-ULT SH10-ULT
NRR NNR

SH10-UMT SH10-UMT
NRR NNR

S27 S27
NRR NNR

S28 S28
NRR NNR

S30-UMT S30-UMT
NRR NNR

S30-ULAT S30-ULAT
NRR NNR

SH10-DMT SH10-DMT S1-CLT S1-CLAT S1-DMT S1A-CLT S1A-DMT SH10-ULT SH10-UMT S27 S28 S30-UMT S30-ULAT 11 11
NRR NNR NRR NRR NRR NRR NRR NRR NRR NRR NRR NRR NRR RWKR NLR 11
RLR
SH10-CLT SH10-CLT
NRR NNR

SH23 SH23
NRR NNR

S26 S26
NRR NNR

02-09-2022 S30-CLAT
NRR
S30-CLAT
NNR
S12 British Interlocking Version 1.0
 13NLR / 13RLR Circuit
S1-DMT S1-DMT S1-CLT S1-CLAT S1A-CLT SH10-CLT S26 S30-CLAT 13 13
B24 NRR NNR NRR NRR NRR NRR NRR NRR NWKR RLR 13 N24

NLR
S1A-DMT S1A-DMT
NRR NNR

SH10-DMT SH10-DMT
NRR NNR

SH-23 SH-23
NRR NNR

S30-CLT S30-CLT
NRR NNR

S1-CLT S1-CLT S1-DMT S1A-DMT SH10-DMT SH23 S30-CLT 13 13

NRR NNR NRR NRR NRR NRR NRR RWKR NLR 13
RLR
S1-CLAT S1-CLAT
NRR NNR

S1A-CLT S1A-CLT
NRR NNR

SH10-CLT SH10-CLT
NRR NNR

S26 S26
NRR NNR

S30-CLAT S30-CLAT
NRR NNR

02-09-2022 S12 British Interlocking Version 1.0

 Point Lock Relay Normal/Reverse (NWLR/RWLR)

The moment point initiation relay for normal (11NLR & 20 NLR) is picked up
then point lock relay for normal NWLR (11NWLR & 20 NWLR) is picked up.
Similarly the point initiation relay for reverse (13RLR , 18 RLR) will pickup point
lock relay for reverse RWLR (13 RWLR &18 RWLR)

NWLR /RWLR picks up by proving following conditions (11NWLR ↑)

•Emergency point key ‘IN ‘checking relay in drop EW(N/R ) CR↓
•ALL signals ASRs in whose route point (No 11) is required are proved in
pickup (S1 ASR ↑, S1A ASR ↑ etc)
•ALL signal OVSR s in whose overlap point (No11) is required , are proved in
pickup
02-09-2022 S12 British Interlocking Version 1.0
 Point Lock Relay Normal/Reverse (NWLR/RWLR)

• Track locking is proved by TPRS in up (11A TPR ↑ , 11B TPR↑)

• Emergency point operation is not initiated (EWNR↓ )
• Individual point button or normal common point button and Reverse common
point Buttons are not in pressed position (11 WNR ↓ 11NWWNR↓ /
RWWNR↓ )
• Automatic point operation is initiated by NLR/RLR up ( 11 NLR↑)
• Point is not set in Normal/Reverse (11 NWKR ↓ )
• RWLR/NWLR in drop (11 RWLR↓)
Note : All the ASRs and OVSRs are proved in by double cutting arrangement.

02-09-2022 S12 British Interlocking Version 1.0

 Point Lock Relay Normal/Reverse (NWLR/RWLR)

26-OV 28-OV 27-OV 11A 11B 11 11 11 11 11 11 28-OV 27-OV 26-OV S26/27/28 SH10 SH23 S1A S1
B24 EW(NR)CR SR SR SR TPPR2 TPPR EWNR NLR RLR WNR NWWNR1 NWKR RWLR WNR 11 SR SR SR ASPR1 ASPR1 ASPR1 ASPR1 ASPR1 N24

NWLR
13 11A 11 13
NWSR1 TPPR2 EWNR NWLR RWWNR2 NWSR2

12 19 11B 11 11 12 19
NWSR1 RWSR1 TPPR WNR NLR NWSR2 RWSR2

S26/27/28 SH10 SH23 11 11

ASR ASR ASR NWLR RWWNR1 RLR

S1 S1A 11 11
ASR ASR RWLR NWWNR1 RWLR NWWNR2

11 11 11 11
WNR RWWNR1 RWKR NWLR WNR 11
RWLR
11A 11B
TPPR2 TPPR 11
W`F'K

02-09-2022 S12 British Interlocking Version 1.0

 Point Lock Relay Normal/Reverse (NWLR/RWLR)

Due to picking up of NWLRS & RWLRS, the following actions takes place
simultaneously.
•NCR/RCR s drop
•NWKR/RWKR s drop
•PCR1,PCR2 pick up
•ASWRs pick up

NCR/RCRs drop:- When the NWLR/RWLR picks up, the RCR/NCR concerned
drop.
For S1 signal to common loop overlap set to main line,
 11RCR , 20RCRs drop (if Point No.11 & 20 are already in Normal) as
11NWLR &20 NWLR are picked up and
 13 NCR and 18 NCRs drop (if Point No.13 & 18 are already in Reverse) as
13 RWLR & 18 RWLR are picked up.
02-09-2022 S12 British Interlocking Version 1.0
 Point Lock Relay Normal/Reverse (NWLR/RWLR)
NCR/RCRs drop:- When the NWLR/RWLR picks up, the RCR/NCR
concerned drop.
11 11 11 11
B24 WWR RWLR RCR NWLR 11 N24

NCR
11
11 NCR
WNR NWWNR1
11 11 11
NWLR NCR RWLR 11
RWWNR1
RCR
11 11
NCR RCR

11
RCR

11 11 11
NLR NWLR NCR 11
ASWR
11 11 11
RLR RWLR RCR

02-09-2022 S12 British Interlocking Version 1.0

 Point Lock Relay Normal/Reverse (NWLR/RWLR)
NWLR RWLR

11 11 11 11 11 11 11 11
11 RWKR NCR WNKR RWR NWR WCR WXR WJR B24
S

NWKR
11 11 11 11 11 11
WNKR RWR NWR WCR WXR WJR N24

11 11
NWLR RWLR

11 11 11 NWKR/RWKR s drop
11 NWKR RCR WRKR
The picking up of NWLR/RWLRs result in dropping of
S

RWKR
NWSRs, RWSRs, NWKPRs, RWKPRs.
11
WRKR The dropping of NCR/RCR (11 RCR ) and picking up of
NWLR/RWLR (11 NWLR) results in dropping of RWKR/NWKR
(11 RWKR↓, NWKR is already in dropped condition).
Therefore the point indication relays and all their repeaters are
dropped.

02-09-2022 S12 British Interlocking Version 1.0

 PCR1, PCR2 pickup
• The moment NWLRs, RWLRs (11 NWLR, 20 NWLR, 13 RWLR↑, 18 RWLR↑)
picks up, the point power control relays PCR1, PCR2 pick up. Then the 110 V
DC for point operation is connected to point location Bus Bar, but 110 V DC
is not connected to point machine. (waiting for18the command from Relay
room) B24 11
NWLR
B24 NWLR
N24
N24

PCR1 18 PCR2
11
RWLR (HEAVY DUTY) RWLR (HEAVY DUTY)
(QBCA1) (QBCA1)
12 19
NWLR NWLR
12
RWLR 19
RWLR
13
NWLR
20
NWLR
13
RWLR 20
RWLR

B110 B110
TO POINTS NO.11.12.13. TO POINTS NO.18.19.20.
LOCATION FOR POINTS LOCATION FOR POINT
N110 OPERATION. N110 OPERATION

02-09-2022 S12 British Interlocking Version 1.0

 Point Chain Group

• The initial currents drawn by the motor is very heavy when compared to the
working current.
• So the battery bank may not withstand if all the points in the route are
allowed to operate at the same time.
• Chain group ensures that the point operation are started with lag.

02-09-2022 S12 British Interlocking Version 1.0

 Automatic Switching of Point Chain Operation Relay (ASWR)

• The energisation of NWLR/RWLRs (11NWLR↑, 20 NWLR↑, 13 RWLR↑,

18 RWLR↑) results in picking up of ASWRs (11ASWR, 20ASWR,13 ASWR &
18 ASWR ) concerned to that route (S1 to CLAT).
• 11ASWR picks up through the front contacts of 11NLR,11NWLR and 11
NCR drop contact.

11 11 11
B24 NLR NWLR NCR 11 N24

ASWR
11 11 11
RLR RWLR RCR

02-09-2022 S12 British Interlocking Version 1.0

 Auto Set Point Relay One- AS1WR

• Auto set point relay AS1WR is normally a de-energised relay and provided
with slow to release arrangement .

• When NLR/RLR ( 11NLR ↑ ,20 NLR ↑ ,13 RLR ↑, 18 RLR ↑ ) and ASWRs (11
ASWR ↑ ,13 ASWR↑ ,18 ASWR↑ ,20 ASWR↑ ) concerned to the
particular route are picked up, then Auto set point relay one AS1WR picks up.

• AS1WR picks up proving the following conditions and sticks through its own
front contact by passing WWFR↓.
 Auto set point relay two in drop (AS2WR↓)
 Auto chain point control relays 11WWR and 12 WWR are in drop
 Auto point operation final normal relay (WWFR ) in drop.

02-09-2022 S12 British Interlocking Version 1.0

 Auto Set Point Relay - AS1WR
B24 11 11 11 12 N24
NLR ASWR AS2WR WWR WWR WWFR

11 AS1WR
RLR
AS1WR
12 12
NLR ASWR

12
RLR

13 13
NLR ASWR

13
RLR

18 18
NLR ASWR

18
RLR

19 19
NLR ASWR

19
RLR

20 20
NLR ASWR

20
02-09-2022 RLR S12 British Interlocking Version 1.0
 Auto Point Operation Relays

Auto point operation final normal relay WWFR :

WWFR is normally a dropped relay. it picks up through 20 WWR ↓ , AS1WR ↑ and
sticks through its own front contact by passing AS1WR↑
Auto set point relay two –AS2WR:
The moment WWFR is picked up, the auto set point relay two (AS2WR) picks up
through WWFR ↑ & AS1WR ↑ and sticks through its own front contact by passing
AS1WR.
Dropping of AS1WR and picking up of 11WWR:-
The moment AS2WR picks up ,AS1WR drops with a time delay .
The moment AS1WR drops it results in picking up of 11WWR through AS2WR↑ ,
WWFR↑ , AS1WR↓ , 13WWR ↓ ,18WWR ↓ ,19 WWR↓ and 20 WWR ↓.
The 11WWR sticks through its own front contact by passing WWFR ↑ and AS1WR ↓.
02-09-2022 S12 British Interlocking Version 1.0
 13 18 19 20
B24 AS2WR WWFR AS1WR 11 WWR WWR WWR WWR N24

WWR
11
WWR

11 11
WWR ASWR 12
WWR
12
WWR

12 12
WWR ASWR 13
WWR
13
WWR

13 13
WWR ASWR 18
WWR
18
WWR

18 18
WWR ASWR 19
WWR
19
WWR

19 19
WWR ASWR 20
WWR
20
WWR
20
WWR AS1WR
WWFR
20
ASWR WWFR

WWFR AS1WR
AS2WR
AS2WR
02-09-2022
S12 British Interlocking Version 1.0
 NWR/RWR CIRCUIT
• With NWLR / RWLR up, all indication relays drop, NCR/RCR up, NWR/RWR will
pick up at location
RELAY ROOM 11 POINT CONTACTOR UNIT LOCATION
11 11
B24 NWSR RWSR

11 11 11 11
RWKR 11
NWKR WNKR RWR
NWR
11 11 11 (QNA1)
11 11 11
NWKPR NCR NWLR
RWKPR NWLR WNKR

11 11
11 11
NCR NWR
NWLR WRKR 11

RWR
11 11 11 11 (QNA1)
RCR RWLR RWLR WRKR

11 11
RCR RWLR

02-09-2022 S12 British Interlocking Version 1.0

 Point Timer Circuit at Location

• With NWR/RWR picks up, WJR picks up.

• There by WXR picks up and sticks with its own front contact.
• With WXR picking up, normal feed to WJR removed but WJR held in pick up
through time delay condenser circuit.

02-09-2022 S12 British Interlocking Version 1.0

 Point Timer Circuit at Location

02-09-2022 S12 British Interlocking Version 1.0

 Point 11 WCR Circuit

• With WXR, WJR, NWR/RWR up and WNKR/WRKR drop, WCR

(QBCAI relay) picks up.

11 11 11 11 11 11
B24
WXR WJR NWR WNKR NWR RWR

11 11
RWR WRKR 11

S
WCR
11 11 11 11 + (QBCA1) -
N24 WXR WJR NWR WNKR

11 11
RWR WRKR

02-09-2022 S12 British Interlocking Version 1.0

 Point Operation Circuit

• With WCR & NWR/RWR up, 110V DC available on bus bar is extended to point
machines at A end & B end parallelly. Both points are set to Normal or
Reverse.

02-09-2022 S12 British Interlocking Version 1.0

 Point Operation Circuit
NC 11
`B'END
NWR
POINT MACHINE

11
RC
RWR

11
NWR
SA

11
RWR

11
NWR 11
NC WCR
`A'END B110
POINT MACHINE

M
11
RC RWR

11 11
NWR WCR
SA N110

11
RWR

02-09-2022 S12 British Interlocking Version 1.0

 Point Indication Circuit at Site

• There by WNKR/WRKR picks up through point machine detection contacts.

`A' END `B' END

11
B24
11 RWR
WNKR
R2 R1
11 NC NC
WRKR N24

11
11 NWR
WRKR
R2 R1
11 RC RC
WNKR

02-09-2022 S12 British Interlocking Version 1.0

 NWKR/RWKR CIRCUIT

• Energisation of WNKR/WRKR results in dropping of WJR, WCR, and

NWR/RWR.
• With NWR/RWR dropping, WXR drops.
• Due to all controlling relays (WCR, WJR, WXR, NWR, RWR) at location dropping
and WNKR/WRKR picking up, energizes indication relay NWKR/RWKR at relay
room.

02-09-2022 S12 British Interlocking Version 1.0

 NWKR/RWKR CIRCUIT
• With NWKR/RWKR picks up which in turn drops NWLR / RWLR.
• Thereby all indication relays& its repeater relays (NWKPRs, NWKSRs) picks
up.
RELAY ROOM 11 POINT CONTACTOR UNIT LOCATION

02-09-2022 S12 British Interlocking Version 1.0

 NWSR/ RWSR Circuit

11 11 11 11 11 11 11 11 11
B24 RWSR1 RWKPR1 RWKPR2
NWLR RWLR NWKR 11 RWSR2 RWSR3 RWKR

R1 NWSR1 R2
11
CH2LPR NWSR1 11

R1 NWSR2
R2

11

R1 NWSR3 R2
11 11
RWLR NWLR N24

11
NWKR

11
RWSR1 11

R1 RWSR2 R2
11 11 11 11 11 11
RWKR 11 NWSR1 NWSR2 NWSR3 NWKPR1 NWKPR2

R1 RWSR1 R2

02-09-2022 S12 British Interlocking Version 1.0

 UCR CIRCUIT

• Once the points are set in to the required position by auto operation of points,
the setting of route is completed.
• To energize the NWKR/RWKR, indicates that the points are set and locked. After
setting the route, it is to be checked. This is achieved by picking up UCR (Route
Checking Relay).

02-09-2022 S12 British Interlocking Version 1.0

 UCR Relay

• Every signal will have one UCR, named after the concerned signal number.
• This relay is normally de-energized relay.
• It energizes when ever signal button and concerned route buttons are pressed.
• Proves points in route, overlap and isolation (set& locked) as required.
• Locking of conflicting signals : By proving Front Contact of ASRs or back contacts of
UCRs of conflicting signals are proved in UCR circuit.
• CH-IN is also proved in UCR , to prevent route alteration by crank handling .
• Concerned to each route NNR↓,NNPR↓,NRR↑ is proved in UCR.
• For Double cutting NRR↑ is proved.
• For cross protection NRR ↓ is proved.

02-09-2022 S12 British Interlocking Version 1.0

 UCR Relay

• UCR back contact is proved in ASR circuit.

• To drop ASR as soon as UCR picks up i.e., to lock the Route as soon as it is
checked.
• Also ensures that Signal is normalized before releasing the route.
• Usage :- UCR front contact is proved in HR circuit.

02-09-2022 S12 British Interlocking Version 1.0

 S30 UCR CIRCUIT
SH10 SH23 CH1 S6 3 4 S1 S1A S3/4 SH21
B24 CH2LPR CH3LPR ASPR2 ASPR1 LPR NRR OVSPR1 OVSPR1 ASPR2 ASPR2 ASPR2 ASPR2

19 12 11 19 12 20
RWKPR2 NWKPR2 RWKPR2 RWKPR2 NWKPR2 NWKPR2

20 12 11 20
RWKPR1 RWKPR2 NWKPR2 RWKPR2

20 19 15 15KL 12 S30-ULT S30-ULT S30-ULT S30A S30-ULT S30-ULAT S30-UMT S30-CLT S30-CLAT S30-ULT
NWKPR1 RWKPR1 KLPR NWKR NWKPR2 NNR NNPR NRR ASPR1 NRPR NRPR NRPR NRPR NRPR NRPR N24

12 S30-ULAT S30-ULAT S30-ULAT S30-ULAT

RWKPR2 NNR NNPR NRR NRPR

19 S30-UMT S30-UMT S30-UMT 12 11 S30-UMT

NWKPR1 NNR NNPR NRR NWKPR1 NWKPR2 NRPR

20 19 18 13 S30-CLT S30-CLT S30-CLT S30-CLT

RWKPR2 NWKPR2 RWKPR2 NWKPR2 NNR NNPR NRR NRPR

13 11 S30-CLAT S30-CLAT S30-CLAT S30-CLAT

RWKPR2 RWKPR2 NNR NNPR NRR NRPR

02-09-2022 S12 British Interlocking Version 1.0

 ASR CIRCUIT

• Whenever a route is set and route-checking relay UCR is energized it

causes ASR to drop and there by locks the route i.e., locks all the points in
the route including in overlap & isolation.
• It is necessary to lock the route before a signal is taken off. Every signal
will have one ASR and the drop contact of ASR is proved in HR pick up
circuit to ensure locking of that signal route before the signal is cleared.

02-09-2022 S12 British Interlocking Version 1.0

 ASR /ALSR CIRCUIT

• ASR/ALSR is a normally energized relay. i.e. Route is free from Approach

Locking
• Every signal will have one ASR .
• Whenever a route is set and route-checking relay UCR is energized it causes
ASR to drop and there by locks the route.
• The drop contact of ASR is proved in HR circuit to ensure locking of that signal
route before the signal is cleared.
• ASR can be combined for the signals which are conflicting to each other

02-09-2022 S12 British Interlocking Version 1.0

 ASR /ALSR CIRCUIT

ASR/ALSR CIRCUIT CONSISTS OF 3 CIRCUITS

• Indication locking.
• Back / Route locking.
• Approach locking

02-09-2022 S12 British Interlocking Version 1.0

 ASR /ALSR CIRCUIT

1 Indication Locking 2 Back Locking 3 Approach Locking

Stick Path

Signal 3
B24 1 Push Button
I/L UCR NRR B/L A/L RECPR N24

ASR
2

ASR ASR Emergency

Sequential Timer Cancellation
Route Relase circuit Circuit
UYR 1,2,3

02-09-2022 S12 British Interlocking Version 1.0

 ASR /ALSR CIRCUIT

ASR gets energized through 3 ways.

(i) Normal Travel of Train on the entire route sequentially and clears the route.
• Train has arrived completely and cleared the entire route.
• sequential route release relays UYR 1,2,3 have picked up indicating the
sequential, directional movement .
• Signal has gone back to `ON’ and the controlling relays & indication relays
have got deenergised.
• Controlling relay(NRR) if any, has been dropped .
• Track circuits in the entire route up to Berthing track have picked up behind
the train.

02-09-2022 S12 British Interlocking Version 1.0

 ASR /ALSR CIRCUIT

(ii) On cancellation,
(a) without any time delay if approach track is provided and clear.
(b) with time delay if approach track is occupied / Not existing
(Dead approach).

(iii) When ever due to any Back locking track circuit failures, the route is locked
(ASR not picked) to cancel the locked route operate calling on Signal initiation
for the same route,there by calling on ASR drops.

02-09-2022 S12 British Interlocking Version 1.0

 ASR /ALSR CIRCUIT

• Immediately calling on Signal is put back to ON and calling on cancellation is

initiated (CO-CAR up).

• Calling on NJPR picks up after 240 seconds time delay which picks up the
Main signal ASR.

• This way the route is released with out S&T Person’s intervention.

02-09-2022 S12 British Interlocking Version 1.0

 S30 ASR CIRCUIT

02-09-2022 S12 British Interlocking Version 1.0

 S30 ASR CIRCUIT

02-09-2022 S12 British Interlocking Version 1.0

 Combined ASR FOR S3&S4

• Every signal will have one ASR. But a signal with Calling ON signal,
and/or a shunt signal below it can have a common ASR.
• Similarly starter signals leading to same route can also have a
common ASR.
• This is purely for economical reasons and the circuits becomes smaller
and no. of relays & wiring can be reduced considerably in major yards.

02-09-2022 S12 British Interlocking Version 1.0

 Combined ASR FOR S3&S4

02-09-2022 S12 British Interlocking Version 1.0

 Overlap Stick Relay Circuits - OVSR & OVJSLR
• OVSR is normally energized and drops whenever the signal is taken ‘OFF’
leading towards that overlap. OVSR UP is proved in the NWLR/RWLR circuit.

3/4 3
B24 ASR OVSR N24
18
NWLR
4
OVSR
18
RWLR

02-09-2022 S12 British Interlocking Version 1.0

 HR Circuit

• The ‘Caution’ aspect of a signal is controlled by HR Circuit.

• At ‘HR’ relay stage, all the conditions to be satisfied for
clearing a signal is proved.

02-09-2022 S12 British Interlocking Version 1.0

 HR Relay

At HR stage all the conditions are to be satisfied for clearing a signal

 Concerned to its own signal i.e.
 RR is up (in case of Home signal)
 NRR concerned to the particular route is proved in its route (path)
 UCR is up-All points in the route, overlap and isolation are set and locked i.e.
Concerned NWKRs, RWKRs are in up condition etc.
 No Route cancellation is initiated i.e. JSLR down.
 ASR is down. Conflicting signals are at ‘ON’ by proving the front contact of
ASRs or back contacts UCRs of conflicting signals.
 One signal - one train feature (TSR up)
02-09-2022 S12 British Interlocking Version 1.0
 HR Relay

At HR stage all the conditions are to be satisfied for clearing a signal

 Crank handles are ‘in’, i.e. proved by CHLRs up and CHFRs down.
 Route Release Relays have de-energized after the last train movement i.e
UYR1, UYR2 etc., are down.
 Interlocked LCs if any in the Route and overlap are locked and closed against
Road traffic (LXPR up) and held locked till the passage of that train .
 All Back lock & and controlling tracks are clear i.e. TPRs concerned are up.
 If any Sectional route release relays TRSR↓ is proved in that particular route.

02-09-2022 S12 British Interlocking Version 1.0

 HR Relay

At HR stage all the conditions are to be satisfied for clearing a signal

 Signal ahead is not blank
 GECR up or
 RECR/HECR/DECR UP
 For Main Line :- Route Indicator lamps are not lit in case of Junction type
Indicator (UHRs / UGRs and UECR down)
 For loop lines:- Route Indicator lamps are lit (UGR or UHR and UECR up)

02-09-2022 S12 British Interlocking Version 1.0

 HR Relay

At HR stage all the conditions are to be satisfied for clearing a signal

 Sidings in the route & overlap are kept normal and held (siding KLPR/NPR up).
 Cross protection is provided for the signal control relay
 by the Front contact of ASR or
 Back contact of UCR.
 Double cutting is provided by UCR up & ASR down.

02-09-2022 S12 British Interlocking Version 1.0

 S30 HR Circuit
CH2 CH2 CH3 CH3 S30 S30 S30 S30ACO 22 SH10 SH23
B24 LPR FR LPR FR UYR1 UYR2 JSLR CAR LXPR ASPR2 ASPR1

19 12 11 19 12
RWKPR1 NWKPR1 RWKPR1 RWKPR1 NWKPR

20 12 11 20
RWKPR1 RWKPR1 NWKPR1 RWKPR1
A

20B 30 S30 S30 S30 S30 S1A CH1 CH1

TPR TPR ASPR2 ASR TSR UCR ASPR1 FR LR

19 27 27 27 UL 15KL 15 12A S27 12 S30-ULT 20

RWKPR1 OVSR OVSPR1 OVSPR2 TPR NWKR KLPR TPPR RECR NWKPR2 RPR NWKPR1

S27 12 S30-ULAT
HECR RWKPR1 NRPR S30
HR

20 19 19 28 28 28 UM S28 S30-UMT 12 12B 11 11B 26-28T S30 20 19 S30 S30 S30 S30 22 S30
NWKPR1 TPPR NWKPR1 OVSR OVSPR1 OVSPR2 TPR RECR NRPR NWKPR2 TPPR NWKPR2 TPPR TPR GNR1 NWKPR1 NWKPR1 UGR UECPR UCR UCR LXPR1 ASPR1 N24

S28
HECR 20 S30 S30
RWKPR1 UGR UECPR
S28
19 18 26 26OV 26OV 20A DECR
NWKPR2 RWKPR1 OVSR SPR1 SPR2 TPPR 19
RWKPR1

18A/B 18A/B 18A 18B

TRSR2 TRSR1 TPPR TPPR1 13 13B 11A S30-CLAT 11 S28 S30 S30
RWKPR2 TPR TPR NRPR RWKPR2 DR HR UECPR

20 18A/B CL 13A S26 13 S30-CLT S28 S28

RWKPR1 TRSR TPR TPPR RECR NWKPR2 NRPR DECPR DECPR

S26
HECR

B7/09 B8/09

02-09-2022 S12 British Interlocking Version 1.0

 S30 HR Circuit

02-09-2022 S12 British Interlocking Version 1.0

 Calling-ON signal
• A Calling-on signal is a subsidiary signal which has no independent aspect in the
‘on’ position and shall be-
(a) a short square ended semaphore arm or
(b) a miniature colour light provided with a ‘C’ marker.

• A Calling-on signal, where provided, shall be fixed below a Stop signal governing
the approach of a train. Under approved special instructions, a Calling-on signal
may be provided below any other Stop signal except the last Stop signal.

• A Calling-on signal, when taken ‘off’, calls on the Loco Pilot of a train to draw ahead
with caution, after the train has been brought to a stop even though the Stop signal
above it is at ‘on’ and indicates to the Loco Pilot that he should be prepared to stop
short of any obstruction.

• A Calling-on signal shall show no light in the ‘on’ position.

02-09-2022 S12 British Interlocking Version 1.0
 Calling-ON signal

Placing and working.—

a) 'Calling-on Signal shall be placed below a Stop Signal governing the approach of a
train. Under approved special instructions, a Calling-on Signal may be provided
below any other Stop Signal except the ,last Stop Signal.
b) The Calling-on Signal shall not be capable of being worked at the same time as the
Stop Signal above or shunt Signal below it, if any.
c) It is desirable to provide track circuits at a suitable distance and a time delay
circuit to ensure that the Calling-on Signal is taken ' OFF ' only after the train has
been brought to a stop.
d) A Calling-on Signal shall detect all the Points in the route, which the main signal
above it detects excluding overlap in double line section. On Single line section
under approved special instructions, a Calling-on signal placed below the first Stop
Signal may not detect points in the overlap.
e) At stations where Station Master controls the reception and dispatch of trains,
such control shall be extended to Calling-on Signals also.
02-09-2022 S12 British Interlocking Version 1.0
 S30A COHR CIRCUIT

02-09-2022 S12 British Interlocking Version 1.0

 SIGNAL LAMP CIRCUIT

a) Based on the condition of signal control relays pick up status (HR,DR), concern
signal aspect Lamp/LED is going to lit at out door with 110 AC supply.
b) Signal Lamp circuits in relay room are designed for lighting the signal Lamp as well
as for checking the Lamp status at out door.
c) Whenever the lamp fuses, then the signal becomes blank and there is a chance
that the driver may miss the blank signal and it may be overshoot. To avoid these
conditions, Cascading method is used.
d) Cascading Method: if a lamp fuses, then the signal can be restored to a more
restrictive aspect. When signal displaying OFF aspect, if OFF aspect lamp fuses
then the signal should restored to next restricted OFF aspect (if Available) or to
ON aspect (if next restricted OFF aspect not available or incase of next restricted
OFF aspect lamp fused) .
e) In RE area, Signal lamp circuits designed with cutting in arrangement.

02-09-2022 S12 British Interlocking Version 1.0

 SIGNAL LAMP CIRCUIT
S1 RELAY ROOM S1/1A LOCATION
B24 HR
S1

S1 HPR
N24 HR

S1 S1
DR HPR
S1
DPR
S1
DR

S1 S1 S1
BX110 HR DR DPR
S1

S1 S1 DG
S1 S1
NX110 HR DR DR DPR
S1
DECR
S1 S1
DECR HPR
S1
S1 S1 HG
S1 HR HPR
DECR S1
HECR
S1
HR S1
RG
S1 S1
DECR HECR

S1
HR S1
RECR
S1 S1
DECR HECR

02-09-2022 S12 British Interlocking Version 1.0

 Button stuck up Relay -NNCR
• NNCR is a normally energized relay.
• When any button is pressed for more than the required time, the relay NNCR
drops to give an audible warning with indication.
• The buzzer can be muted but the indication continues to glow till the fault is
rectified.
• The NNCR relay is provided with a condenser to hold the relay in energized
condition for a specific time period. Even if any button is pressed, the NNCR
will not drop immediately. But if the button is pressed for more time or stuck
up, then NNCR will drop and activates Buzzer cum indication circuit.

02-09-2022 S12 British Interlocking Version 1.0

 Button stuck up Relay -NNCR

02-09-2022 S12 British Interlocking Version 1.0

 Button stuck up Failure Buzzer & Indication Circuit
B24 BUTTON STUCK
NNCR ACK N24
P
(NO) R1
ACKNR R2
NN
ACKNR

NN
ACKNR BUTTON STUCK N24
BUZZER

BUTTON STUCK

K(R)

02-09-2022 S12 British Interlocking Version 1.0

 Point Indication Failure Relay - WXJR

• WXJR is a normally energized relay.

• When any point indication is not available, WXJR will drop and gives buzzer &
indication. Buzzer is muted but indication persists.
• Relay WXJR is made slow to release to prevent if from dropping during
operation of point from N-R (or) R-N. Only after a specified period, still point
indication is not available, then WXJR will drop.

02-09-2022 S12 British Interlocking Version 1.0

 Point Indication Failure Buzzer & Indication Circuit

B24 WX
WXJR ACK WX N24
P
(NO) R1
ACKNR R2
WX
ACKNR

WX
ACKNR WX N24

BUZZER

WX

K(R)

02-09-2022 S12 British Interlocking Version 1.0

 Signal Lamp Failure Indication Relay - GXJR

• The relay GXJR is a normally energized relay.

• When all the signals in the yard are displaying any one of the aspects, then
GXJR will remain up.
• If any signal becomes blank, then GXJR will drop giving Buzzer and visual
indication. Buzzer can be muted, but indication will remain, till the fault is
rectified and GXJR is energized.
• Relay GXJR is made slow to release to prevent it from dropping during the
change over period of aspects.

02-09-2022 S12 British Interlocking Version 1.0

 Signal Lamp Failure Indication Relay - GXJR

02-09-2022 S12 British Interlocking Version 1.0

 Signal Lamp Failure Buzzer & Indication Circuit
B24 STN. STN.
GXJR GX ACK STN.GX N24
P
(NO) R1
ACKNR R2
STN.GX
ACKNR

STN.GX
ACKNR STN.GX
BUZZER

STN. N24
GXK(R)

02-09-2022 S12 British Interlocking Version 1.0

 CRANK HANDLE INTERLOCKING CIRCUITS (CHLR/CHRR)

• Where point motors operate points, crank handles are provided to

facilitate operation of points mechanically (manually) in case of point
failure.

• The manual operation of point, after a signal is cleared, may endanger

the train operation. Therefore, it is necessary that crank-handle be
interlocked with signals suitably.

• CH1 group covers point No 13 & 18; CH2 covers 11, 20 and CH3
covers 12, 19 points.

02-09-2022 S12 British Interlocking Version 1.0

 Crank Handle Free Relay –CHFR

• When the concerned signals are at ON (NRRs down), there by CH1FR will be energized
through NRR back contacts. Then crank handle free indication will be in lit condition in the
‘CH’ box and gives indication to SM on the panel also. (CH1 can be extracted if need arises).
• Whenever any of the signals concerned is taken OFF, the NRR concerned Picks up and
causes to drop CH1FR. There by Crank handle free indication extinguishes and SM
understands that CH1 can be not be extracted unless the signal is normalized.

02-09-2022 S12 British Interlocking Version 1.0

 Crank Handle IN Proving Relay – CH1CR/CHLR

• In the EKT, while the key is inserted and being turned to RH side contact No.1,
2 and 3, 5 will be made and CH1CR will be picked up.

• Once the turning is over and the key is left, contact Nos.1&2, 3& 4 will be
made and CH1CR held in picked up condition through stick path.

• SM will ack by pressing CH1 and GSRBN buttons causing to pick up CHLR in the
relay room and SM gets crank handle IN indication on the panel.

• CHLR front contact is proved in UCR & HR circuits.

02-09-2022 S12 British Interlocking Version 1.0

 Crank Handle IN Proving Relay – CH1CR/CHLR

• When S1 signal is taken OFF for main line S1 DMT NRR pick up there by S1 ASR
drops and causes to drop CH1FR.

• At that moment if SM tries for extraction of crank handle by pressing CH1 and
GSBN buttons CH1RR does not pick up, there by CH1LR does not drop as feed
extended to CH1LR through CH1RR back, CH1CR Front contacts and held
through stick path.

• As CH1LR not dropped, Lock coil in EKT does not energized , thereby crank
handle key cannot be extracted. At the same time, the signals taken off remain
in the same condition.

02-09-2022 S12 British Interlocking Version 1.0

 Crank Handle IN Proving Relay – CH1CR/CHLR

30-CLT 30-CLAT S30A-CLT 26 S1-CLT S1-CLAT S1-DMT S1A-CLT S1A-DMT S3 S4

B24V NRR NRR NRR NRR NRR NRR NRR NRR NRR NRR NRR
A

SH10-CLT SH10-DMT SH21-CLT SH21-DMT SH23 CH1

NRR NRR NRR NRR NRR NR GSBNR CH1 N24V
A
RR
CH1 CH1 R1 R2
NR RR

GS
RBNR

02-09-2022 S12 British Interlocking Version 1.0

 Crank Handle IN Proving Relay – CH1CR/CHLR
SEALED

CH1 CH1 CH1 CH2 CH3 CH

RR LR NR GSBNR CH1FR CH1 JSLR JSLR NJPR N24V

JSLR
CH1 R1 R2 CH1
JSLR JSLR

POINT No: 13 & 18

CH1 CH1 CH
FR JSLR NJPR CH1
COUNTER
CH1 CH1 CH1 CH1
CH1 LR CR FR RR CH1EKT CH1LPR
P
L
(NO)

B24V 1 2 3 4 5 N24V

CH1CR
R1 R2

CH1
B24 JSLR IP COM N24
CH1 CH1
CH1 JSLR CR CH1
P
TIMER
(NC)
OP 120SEC
CH1RR
ON PANEL ON CH BOX CH
CH CH1 R1 NJPR R2
B12V NJPR JSLR CH1 N12V NJPR N12V
CH
F'K' JKE
CH1
FR
CH1 N12V

F'K'
02-09-2022 S12 British Interlocking Version 1.0
 Crank Handle IN Proving Relay – CH1CR/CHLR

CH1 CH1 CH1 GS

B24V RR CR NR RBNR CH1 N24V

R1 LR R2

CH1 CH1
LPR LR CH1

R1 LPR R2

02-09-2022 S12 British Interlocking Version 1.0

 Crank Handle Indication Circuits

ON PANEL ON CH BOX

CH CH1
B12V NJPR JSLR CH1 N12V

F'K'
CH1
FR
CH1 N12V

CH1 F'K'
LR CH1
K(W)

CH1

CH1 K(W)
LR CH1
K(R)

CH1
K(R)

02-09-2022 S12 British Interlocking Version 1.0

 Interlocking of Level Crossing Gate

• SM communicates to the gateman on phone to close the gate.

• The gateman closes the gate, locks the boom and extracts key.
• The gateman inserts the in key in EKT and turns it clockwise to transmit
control.
• Thereby LXR relay energizes & sticks through its own front contact.

02-09-2022 S12 British Interlocking Version 1.0

 Interlocking of Level Crossing Gate

02-09-2022 S12 British Interlocking Version 1.0

 Interlocking of Level Crossing Gate

• Energisation of LXR relay at gate lodge energizes LXCR at relay room.

02-09-2022 S12 British Interlocking Version 1.0

 Interlocking of Level Crossing Gate

• Due to LXCR up & LXPR in drop, flasher supply 12V DC will be

connected to LC closing indication LXKE (G) and it flashes.
• There by SM comes to know that LC gate was closed by gateman.
• Then SM acknowledges by pressing ‘LXN’ and ‘GSRBN’ which
results in dropping of LX22-NRR.

02-09-2022 S12 British Interlocking Version 1.0

 Interlocking of Level Crossing Gate

02-09-2022 S12 British Interlocking Version 1.0

 Interlocking of Level Crossing Gate

02-09-2022 S12 British Interlocking Version 1.0

 Interlocking of Level Crossing Gate

• The dropping of LX22-NRR, results in dropping of LXYR.

• Due to LX22-NRR drop, LXYR also drop, LXCR already in up, and
LX22 JSLR normally dropped relay result in energisation of LXPR
relay.
• LXPR front contact proved in concerned HR/DR Ckt.

02-09-2022 S12 British Interlocking Version 1.0

 Interlocking of Level Crossing Gate

02-09-2022 S12 British Interlocking Version 1.0

 Interlocking of Level Crossing Gate

• The moment signal is cleared, the ASR concerned drops which

ensures the 22LXFR to drop.
• Thereby as long as the signal is in taken off condition, LXYR does
not pick up and thereby gateman cannot open the gate, even if SM
inadvertently transmits the LC gate control by pressing LXN and
GSBN.

02-09-2022 S12 British Interlocking Version 1.0