Detail about Token less Block Instrument

1. 1
S&T workshop/PTJ presents the Manual for Tokenless Block Instrument Mark II
with ‘Q’ relays. Tokenless Block Instrument with ‘Q’ Relays have been found to provide
more reliable and failure free service and this Manual is aimed that understanding
principles of this instrument and its working concept more clearly.
We from S&T Workshop/PTJ look forward to your valuable suggestions and
comments that may further improve this instrument. The comments/suggestions may be
directly sent to the address mentioned below.
“Chief Workshop Manager,
S&T Workshops/S.Rly/Podanur
Coimbatore Dist – 641 023.
FAX: 0422-2413036 & 2413266
E-Mail: cwmptj@sa.railnet.gov.in
HOME PAGE: www.irsignal.com
We suggest that a careful study of the Manual may be undertaken before installation of
the instrument to obtain failure free and reliable service from the Block instrument.
Chief Workshop Manager,
S&T Workshop / Podanur.
FOREWARD

2. 2
CONTENTS __________________________________________
1. INTRODUCTION. 3
2. SYSTEM OF WORKING. 3
3. BRIEF DESCRIPTION OF PUSH BUTTONS AND INDICATIONS Etc. 4
4. BRIEF FUNCTIONAL DESCRIPTION OF RELAYS. 6
5. POWER SUPPLY ARRANGEMENT. 14
6. GUIDE LINES FOR THE INSTALLATION AND MAINTENANCE. 15
7. TECHNICAL KNOWHOW. 16
8. TROUBLE SHOOTING METHODS 17
9. SEQUENCE CHART FOR RELAY WORKING 18
10. INSTRUMENT CIRCUIT DIAGRAM (DRAWING No. TLB 00101) 23

3. 3
1. INTRODUCTION
Tokenless block instruments confirming to Indian Railway Standard Specifications No: S 32/66
are being manufactured at S&T Workshop, PODANUR, S.Railway as per circuit diagram
No.TLB 00101. These Insts are installed on single line sections in all over Indian Railways.
This increases the Line capacity without changing the basic requirements of absolute block
working by
1. eliminating tangible authority
2. minimizing operating time and
3. incorporating non co-operative feature
However, for canceling a line clear – either normal or push back- active cooperation of both end
operators is essential. This instrument does not have any mechanical moving parts and the
safety in train working is achieved by Relay interlocking. Hence it is also named as Relay
automatic block instrument. These instruments are generally worked with metallic return.
2. SYSTEM OF WORKING
Three stepped DC polar pulse is employed in this instrument to achieve cent percent immunity
to all types of contact faults/interference in its line circuit. All functionary codes begin with
negative pulse while for bell, a single positive is used.
2.1 FUNCTIONAL CODES
Bell +
Train coming from - + -
Train going to - - +
Train on line - - -
Line Closed - + +
2.2 Clearing of Last Stop Signal is the only authority for the driver to enter along with his
train into block section which is controlled by this inst. It is possible to clear the LSS only
after setting this instrument to “Train going to” condition this signal is also replaced to
“on” Automatically by the entry of the train into the block section
.
2.3 The actuation of FVT with the instrument in TGT condition sets the
Instruments at both the ends to “Train on line” condition with an intermittent audible
warning at the train receiving inst. and re-clearance of LSS is not at all possible with the
instrument in TGT-TOL condition.
2.4 Arrival of a train is notified with a continuous audible warning at the train receiving end.

4. 4
3 .BRIEF DESCRIPTION OF PUSH BUTTONS, INDICATIONS ETC
3.1 PUSH BUTTON/THUMB SWITCHES.
Push button switches are provided for manual operation of this instrument by the Station Master.
The switches used and their functions are furnished below.
3.1.1. “BELL CODE” BUTTON: CODE – BCB, COLOUR – BLACK
The function of this button is to draw the attention of the other end Station Master. It is also
used for performing all manual operations. Its contacts are repeated by a relay – BCBR. When
pressed alone, it closes the bell circuit and if pressed along with TGB, the instrument can
transmit TCF code and receive TGT code. When pressed along with LCB, it can transmit and
receive line closed code. With inst. In TGT condition if pressed along with cancellation button,
it initiates cancellation operation by advancing the counter number by one higher number and
put back the LSS to “ON” if cleared already.
3.1.2 “TRAIN GOING TO’ BUTTON: CODE – TGB, COLOUR - GREEN
The function of this button is to set an Instrument to TGT condition button to be pressed along
with the BCB to set the instrument to Train going to condition i.e. used to transmit TCF code
and to receive TGT code. Its contacts are repeated by a relay-TGBR. If pressed alone, it closes
ASTR relay circuit and if pressed during the transmission of TOL code, it stops TOL code
transmission temporarily to facilitate to call the other end station master.
3.1.3 “LINE CLOSED” BUTTON: CODE – LCB, COLOUR WHITE
The function of this button is to set an Instrument to Line Closed condition but to be pressed
along with BCB i.e. used to transmit and receive line closed code. If pressed alone it has no
effect. Its contacts are repeated by a relay - LCBR.
3.1.4. “SHUNT KEY” BUTTON: CODE-SHK, COLOUR-BLUE
The function of this button is to extract shunting key which in turn controls a relay-SHKR -for
performing shunting beyond Starter signal. Extraction of this key is possible only in line closed
or TGT-TOL condition by pressing this button and this makes the instrument inoperative from
further functions.
3.1.5. “SLIP/CATCH SIDING KEY” BUTTON: CODE: SCK, COLOUR- BLUE
The function of this button is to extract Slip/Catch siding point control key – which in turn
controls a relay-SCKR. Extraction of this key is possible in all position other than line closed
condition by pressing this button and makes the instrument inoperative from other functions.
3.1.6 “CANCEL” BUTTON: CODE-CANCEL, COLOUR-RED
The Function of this button is to cancel the Line Clear already established in an Inst. through a
controlling relay-CAR. It is required to be pressed along with BCB only for this purpose. While
doing so, it makes the cancellation counter to advance by one higher number and puts back the
LSS to ON, if cleared already. Two types of cancellations are available- Normal cancellation
and push back cancellation. The normal cancellation is effective after 120 secs where as push
back cancellation is effective immediately.

5. 5
3.1.7 SM’S KEY & SWITCH: CODE-SMK, COLOUR-GREEN
This switch is used to prevent unauthorized operation of the Inst. The SM’s switch is having
N&R positions and provided with a key locking facility. The key can be extracted only in R
position. Once the switch is turned to “R”, the manual operation of the instrument is ineffective.
i.e. initiation of Line closed or TCF code or bell beat is not possible, but it is still possible to
receive TCF or line closed code or transmit and receive TOL code or transmit answer back TGT
or Line closed code or receive bell beat. Thus the non-cooperative feature is not destroyed by
locking this instrument.
3.2 PANEL INDICATIONS - all LEDs
These indications are provided for the guidance of the operator.
3.2.1 LINE CLOSED – (2 YELLOW/WHITE)
This indication will be normally lit when the Inst has not been set to TCF or TGT i.e. the Block
section is closed. It starts flashing during code progress.
3.2.2. TRAIN COMING FROM – (2 GREEN)
This indication will lit only if the Instrument is in TCF condition and starts flashing during the
progress of other codes.
3.2.3. TRAIN GOING TO – ( 2 GREEN)
This indication will lit only if the Instrument is in ‘TGT’ condition and starts flashing during the
progress of other codes. Among these three any one will lit based on the Inst. Condition
3.2.4 TRAIN ON LINE – (2 RED)
This indications will lit automatically on occupation of the Block section provided the Inst.is in
TGT or in TCF condition. Once lit, it will remain in that position till the Inst is set to line closed
condition. In TGT, this indication appears as soon as the train entered into the block section and
in TCF; it appears only on receipt of 2nd
TOL pulse.
3.2.5 L.S. Signal (1 RED & 1 GREEN)
These indications are provided to notify the Aspect of the Last Stop Signal to the Operator.
When lit, ‘RED’ means that the last stop signal is ON and ‘GREEN’ means that the signal is
OFF.
3.2.6. SNR - 1 YELLOW / WHITE.
This is normally lit and proves that the signals and their control slides/ levers/ knobs pertaining
to that block section are in normal position.
3.2.7. “FREE” – (2 GREEN).
This indication is provided to notify the operator that the prescribed time interval of 2.0 minutes
on cancellation of Line Clear has lapsed and cancellation operation can be commenced. It
appears only in TGT condition and not in TOL condition.
3.3 COUNTER
It is a non re-settable six digit counter, used for the purpose of registering all cancellation
operations carried out in this instrument. For each cancellation the counter advances by one
higher number immediately.

6. 6
4. BRIEF FUNCTIONAL DESCRIPTION OF RELAYS
35 Nos. of relays are housed in this Inst. relay cabinet. Besides these relays, four timer units-
consists of condensers, resistors etc. and one 120 sec. electronic timer are also housed in it for
effecting the required time delays on certain relays as required by the circuitry.
The relays employed in this instrument and their numbers, types etc. are furnished below:
No. TYPE DESCRIPTION CONTACTS TOTAL
i). QN1 NEUTRAL LINE RELAY 8F/8B 28
ii QLI LATCH RELAY 8F/6B 4
iii QB3 BIASED LINE RELAY 4F/2B 3
iv ET ELECTRONIC TIMER --- 1
v -- CONDENSER UNIT --- 4
These relays and their circuits are grouped based on their functions and the power supply used.
The power sources required for this Inst. working are i) Location battery ii) Line battery and iii)
Local battery. Accordingly the circuit is divided and respectively named as External circuit,
Line circuit and Local circuit. For Telephone, separate power source is used
4.1 EXTERNAL CIRCUIT RELAYS
This circuit is used to ensure and achieve the highest safety in train working. Hence monitoring
of the Field conditions such as, i) Normal position of Reception and Dispatch Signals and their
controls, ii) Entry / occupation of Block section by a train and iii) Clearing of Block section by
a train through the Inst. are incorporated in this circuit by using field / external source. In case
of panel interlocked / RRI stations, field / external battery can be dispensed and selection
battery supply can be used for this circuit.
The relays used in this circuit are i) SNR ii) ASTR iii) TAR
4.1.1. SNR – SIGNAL NORMAL RELAY TYPE: QN1 – 8F/8B
This relay proves the normal position of all the signals and their control levers/knobs pertaining
to that block section. It picks up by pressing BCB along with TGB/LGB buttons or
automatically on receipt of all 2nd
functional pulse except on TOL code and drops at the end of
3rd
pulse. However, if the Inst. is set to TGT, it drops only on releasing LSS control. Picking up
of this relay indirectly proves that shunt key and slip siding /catch siding keys are IN position.
Normal position of first vehicle and Last vehicle tracks etc. are also proved in this relay circuit.
For all functions except TOL and Bell transmission this relay working is a must. Though feed
to this relay from the external circuit is available, it does not picks up due to No drain circuit
feature. However, SNR indication is available.
4.1.2. TAR – TRAIN ARRAIVAL RELAY. TYPE: QLI - 8F/6B
It is a magnetic latch relay and used for registering the arrival of a train on line clear. It picks up
through the external selection battery while receiving a train on signals with instrument in TCF-
TOL / TGT-TOL condition and de-latches to normal through local battery once the instrument
assumes to line closed position, i.e. only on receipt of line closed code

7. 7
4.1.3. ASTR - ADVANCED STARTER TRACK RELAY. TYPE: QN1- 8F/8B
It is a repeater for the First vehicle Track relay and can be pick up whenever the TGB is pressed
and sticks once TGT is established. It drops once FVT is actuated. Dropping of this relay in
TGT position initiates transmission of automatic TOL code along with TOL code along with
TOL indication. It also picks up and sticks while initiating push back cancellation. Non
energisation of this relay will not permit the Inst. to change to TGT even on receipt of Answer
back TGT code.
4.2 LINE CIRCUIT RELAYS - TYPE: QB3 – 4F/2B
This circuit is used to electrically interconnect two Inst. The relays used in this circuit are
biased line relays – named as CRR and TCKR and can operate only if its coil terminal R1 is
+ve. The relay CRR of one Inst. is connected in series with the relay TCKR if the other Inst. by
means of over head lines or cables. Picking up & dropping of CRR and TCKR at their respective
ends initiates another relay LR in the respective Inst. which in turn activates the code
progressing relays – 1CR, 2CR, and 3CR. These relays are fed from Line Battery and require
60 ma. Line current.
4.2.1 CRR – CODE RECEIVING RELAY
It is used for sensing the polarity of the line current received at the code receiving Inst. As this
relay picks up only with a particular polarity of current. Two such relays are connected parallel
with diodes in series in such a way that only one pick up at a time.
The relay which picks up for positive polarity is named as CRR-N and the other which picks up
for the negative polarity is named as CRR-R (these relays are fed from other station) The use of
diodes in these relay circuits prevents sharing of line current by both these relays initially.
4.2.2. TCKR – TRANSMISSION CODE CHECKING RELAY.
It is used for sensing the working of the interconnected instrument at the other end of the Block
section. The same Inst. Line Battery is fed to this relay. This relay comes in to the line circuit
only for the functional codes and not during Bell beat.
4.3 LOCAL CIRCUIT RELAYS
This circuit is the heart of this Inst. and divided into number of sub sections based on their
functions. These relays are named according to their functions.
4.3.1 CTR – CODE TRANSMISSION RELAY. TYPE : QN1- 8F/8B
This relay by its state of energisation or de-energisation decides respectively whether the
instrument is in transmitting or receiving mode. Pick up of this relay proves that all the required
conditions for transmission of a code are available i.e.
i. All reception and dispatch signals and their control levers/ slides/ knobs
pertaining to an Instrument is normal.
ii. No shunting is being carried out in the face of a train and
iii. SM is keeping the required buttons i.e. BCB along with TGB or LCB in the pressed
conditions with the SM switch is in normal.
iv. The conditions are favorable for answering back.

8. 8
This relay circuit is having five branches – Two for manual initiations of codes – TCF/LC. Two
for answer back initiation of codes – TGT/LC and one for initiation of automatic TOL code.
Once picks ups it retains up during the transmission of a code with the help of its time delay
arrangement. Its front contacts connect the line battery to the line while the instrument
transmitting and its back contacts connect CRR to the line while the instrument is receiving. The
time delay circuit checks the duration of the ON and OFF period of a pulse. Due to any reason
either at the transmitting or receiving end if the coding circuit functions irregularly
resulting prolonged duration of ON/OFF period, this relay de-energizes and reinitiates the
same code after a predetermined time provided that the code initiation is manual.
4.3.2 CTPR – REPEATER OF CTR. TYPE: QN1- 8F/8B
It is used as a repeater relay for CTR but picks up only during the ON period of 2nd
pulse and
held in up position for a specified period even after CTR relay drops for receiving answer back
code. This relay is specially introduced to
i. Ensure that the answer back TGT code is received within the pre determined time-
decided by CTR after transmission TCF code and
ii. Ensure that transmission of TOL code can not be stopped before setting the TCF Inst. to
TOL position.
A time delay circuit is used to keep this relay in the energized position during the inst. change
over period (i.e. from transmit to receive). If the other instrument while answering back does not
respond within the pre determined time, this relay releases and initiates code transmission afresh
provided transmission is manually initiated. The front contact of this relay along with BCBR up
in CRR circuit and in TOLAR de-latch coil circuit respectively ensures the above said
conditions. Its back contact in TGBR, SHKR and CRR circuits ensures that setting of both
instruments to TGT at a time by any means is made impossible.
4.3.3 PTR AND NTR – POSITIVE AND NEGATIVE TRANSMITTING RELAYS TYPE: QN1- 8F/8B
These relays are used respectively to connect positive / negative of the line battery on line at the
transmitting instrument. Only one relay can pick up at a time and this depends on the conditions
of the coding relays 1CR, 2CR, 3CR and the Inst. position deciding relays TCFR and TGTR
provided the relay CTR is in energized conditions. Once TCKR is picked up the relay
PTR/NTR sticks through its front contact to ensure the presence of a pulse on line till the line
circuit is opened either by the receiving instrument or by the transmitting instrument itself by
dropping of the relay CTR. The 2nd
case takes place only if the receiving Inst. fails to open the
line circuit at the end of a pulse.
4.3.4 RCKR – RECEPTION CODE CHECKING RELAY. TYPE: QN1- 8F/8B
The function of this relay is to terminate a pulse that is received by opening the line circuit at the
receiving end. It is also used to pick up the relay CTR for answering back code transmission.
Picking up and dropping of this relay respectively opens and closes the line circuit. The
different position of code progressing relays-1CR, 2CR and 3CR closes this relay circuit. This
relay has got two release time lag circuits one with 220 mfd condenser and the other with 470
mfd condenser. The first one is effective during the first and second pulse. Off periods and the

9. 9
second one along with the first one (added together) is effective at the end of third pulse to
enable CTR to pick up for answer back code transmission as well as to prolong the TOL buzzer
at the end of TOL 3rd
pulse in TCF Inst. As the code progressing relays 1CR, 2CR and 3CR are
working in both the Insts. during transmission and reception of a code and the RCKR relay
circuit manly depends on these relays positions this relay RCKR also picks up once at the code
transmitting end i.e. on completion of 3rd
pulse.
4.3.5 RDR – RECEPTION DELIVERY RELAY. TYPE: QN1- 8F/8B
This relay is used to register and store the first negative pulse of a code that is received. Once
picks up it remains in that position till the relay 3CR drops. Its front contact is proved in all
code registering relays circuits – TCFR, TGTR and LCCPR. Proving of CTPR relay up contact
in this relay RCKR circuit ensure the timely reception of answer back line closed code.
4.3.6. LR – LINE RELAY. TYPE: QN1- 8F/8B
This is the first relay to pick up after picking of CRR or TCKR. It works both in transmitting
and receiving Insts. Picking up and dropping of this relay at respective Insts. During each pulse
activates the code progressing relays in the respective Insts. The feeding circuits of this relay
consists of two branches one with TCKR and PTR/NTR contacts –effective while transmitting
and other with CRR(N) and LPR front contact – effective while receiving. Its back contact used
in CTR time delay circuit helps to reset CTR in case the “ON” period of a pulse is prolonged or
termination of a pulse is delayed at the receiving end.
4.3.7. LPR – REPEATER OF LR. TYPE: QN1- 8F/8B
This relay is a repeater for LR relay but with a difference of remaining up even during the
release period of LR by means of a time delay circuit and drops only at the end of 3rd
pulse.
This relay operates both in transmitting Inst. and receiving Inst. At the transmitting Inst. it is
used to monitor the duration of “OFF” period of a pulse. If the appearance of the next pulse on
line or the duration of the “OFF” period of a pulse is prolonged beyond the pre determined time
due to any reason, this relay releases and resets CTR even if the code progress is in half way. At
the receiving Inst. its back contact closes the bell circuit whereas the front contact in CRR
circuit ensures latching of that Inst, for onward reception of 2nd and 3rd incoming pulse, i.e.
disturbance of BCB button after 1st pulse will have no effect. As this relay is also used to reset
all the code progressing relays-lCR. 2CR. and 3CR. a zenar diode is provided across its
condenser to have a constant time delay irrespective of local voltage variations.
4.3.8. 1 CR, 2CR AND 3CR-.-CODE PROGRESSING RELAYS: TYPE: QNI- 8F/8B.
These relays are named as- code progressing relays and common for both transmitting and
receiving Insts. These relays pick up and drop in a predetermined manner to progress the coding
m both Insts. and energisation or de-energisation of these relays mark the various stages of
coding in an Instrument. Among these relays ICR is having two branches of circuit (similar to
LR) -one with TCKR and the other with RDR respectively effective during transmission and
reception of a code. A zenar diode is provided across the condenser of 3CR relay to have a
constant time delay irrespective of the voltage variations as it is used to reset the relays like
RDR. RCKR etc.

10. 10
The following table shows the various conditions of the code progressing relays along with LR
and LPR during code progressing periods.
-----------------------------------------------------------------------------------------------------------------
1st pulse 2nd pulse 3rd pulse
ON OFF ON OFF ON OFF
1 CR UP UP UP UP DOWN* DOWN
2 CR DOWN UP UP DOWN DOWN DOWN
3 CR DOWN DOWN UP UP UP DOWN**
LR UP DOWN UP DOWN UP DOWN
LPR UP UP UP UP UP DOWN**
-----------------------------------------------------------------------------------------------------------------
Note: i. * During the ON period of third pulse though, the feed is cut off. the relay lCR is held
in the energised position for a specified time. Due to this time delay, the latch coil of the
relay-TCFR/TGTR and other relays- LCCPR/ASR/TOLTR gets energized.
ii. ** 3CR & LPR relays will not drop immediately at the end of 3rd pulse even though
there is no feed due to time delay arrangements.
4.3.9. P2R, N2R – SECOND POSITIVE & SECOND NEGATIVE PULSE
REGISTERING RELAYS. TYPE :QNI 340 OHMS.
These relays are used to register and store the second pulse of a code that is being received.
Once picked up. it drops only after the reception of 3rd pulse, i.e. on dropping of lCR relay. The
relay N2R is used to register the 2nd negative pulse whereas the relay P2R is used to register the
2nd positive pulse. Front contact of these relays is used respectively in TGTR and TCFR latch
coil circuit. Further, picking up and dropping of N2R relay in a TCF Inst, causes TOLAR to de-
latch to displays TOL indication long with an intermittent buzzer in that Inst, picking up of P2R
relay closes SHKR circuit which in turn closes the other related relays circuits to set an Inst, to
TCF condition.
4.3.10. TOLAR - TOL ACKNOWLEDGEMENT RELAY: TYPE: QLI -8F/6B.
It is a magnetic latch relay having two different functions.
I . To initiate automatic transmission of TOL code and to stop the same on receipt of its
Acknowledgement.
Ii . To display TOL indication on receipt of TOL code.
The former is effective in TGT Inst, whereas the latter is effective in TCF Inst. It picks up only
on receipt of 2nd TCF / TGT pulse and de-latches on receipt of 2nd TOL pulse in TCF Inst, and
on receipt of TOL acknowledgement in TGT Inst. In case, if an Inst, does not change to TCF/
TGT on receipt of the respective codes, it assumes to its normal position automatically at the
end of the 3rd pulse. Introduction of its front contact in CTR circuit initiates transmission of
answer back TGT code. Its from contact in TOLTR circuit initiates transmission of TOL code.

11. 11
4.3.11 PCR - POLE CHANGING RELAY. TYPE: QNI- 8F/8B,
The function of this Relay is to initiate "Line Closed" code by changing the polarity of 2nd and
3rd
pulses as positive, for setting the instrument to the Line Closed condition. This Relay picks
up after 120 secs. during normal cancellation and immediately on push back cancellation or on
reception train.
4.3.12. ASR - ADVANCED STARTER RELAYS. TYPE: QNI -8F/8B.
The function of this relay is to monitor FVT track from the time of setting an instrument to TOT
and also to ensure positive display of TOL indication as well as transmission of auto TOL code
on occupation of FVT. Dropping of this relay on occupation of FVT displays TOL and initiates
transmission of TOL code. This Relay picks up only on receipt of 3rd TGT pulse provided
CTPR is in up and the buttons BCB & TGB kept in pressed condition. CTPR up ensures timely
reception of answer back code and BCBR up ensures CONTINUOUS pressing of these buttons.
Its front contacts is used in tie TGTR latching circuit as well as in its stick circuit. Once dropped
it will not pick up unless the Inst. receives a fresh TGT reply code which is possible only after
setting that Inst, to Line Closed condition either by canceling the line clear or on complete
arrival train.
4.3.13. TCFR - TRAIN COMING FROM RELAY. TYPE : QLI- 8F/6B.
This is a magnetic latch Relay and used to display LC/ TCF condition of the Instrument
continuously. It picks up on reception of TCF code and de latches on receipt of Line Closed
code with BCB & LCB buttons in the pressed condition and SM switch is in Normal position.
Latching of this relay ensures
i. Reception and despatch signals and their control levers / slides / knobs pertaining to that
block section are in normal,
ii. No shunting is being carried out.
iii. TCF code is received correctly and
iv. The instrument will certainly display TOL condition once the train enters in to the block
section.
4.3.14. TCFPR- REPEATER OF TCFR. TYPE: QN1- 8F/8B.
It is introduced to have additional contacts of TCFR relay.
4.3.15. TGTR- "Train Going To" Relay. Type: QL 1- 8F/6B.
It is a magnetic latch relay and used to display LC/TGT condition of the Instrument
continuously picks up after the relay ASR is picked up on successful reception of TGT code and
with BCB & TGB m pressed condition. It de-latches on receipt of "Line Closed" code with or
without pressing BCB & LCI J buttons. The former is required only during Cancellation.
Latching of this Relay ensures
i. The Inst receives TGT code as an answer back reply code within the pre- determined
time interval from the time of TCF code transmission.
ii. The FVT is clear.
iii. The operator is continuously beeping the buttons BCB and TGB in the pressed condition.
iv. The reception and despatch signals pertaining to this block instrument are normal
Including their control levers/slides/knobs etc.
v. No shunting is performed, and
vi. The Inst will positively display TOL and transmit automatic TOL code once FVT is
Occupied.

12. 12
4.3.16. TGTPR- REPEATER OF TGTR TYPE : QN1- 8F/8B.
It is introduced to have additional contacts of TGTR relay.
4.3.17. TOLTR- TOL CODE TRANSMUTING RELAY. TYPE:ON1- 8F/8B.
This relay is used to transmit automatic TOL code WITH the Inst, in TGT and the Block Section
is occupied. It also initiates an audible buzzer in TCF Inst, on receipt of TOL code. In TGT
condition, this Relay picks up when FVT is actuated and initiates automatic transmission of
TOL code and drops only if the same is acknowledged. In TCF Inst, it picks up on complete
reception of TOL code and drops at the end of TOL code. During this period the TOL buzzer
sounds Intermittently.
4.3.18. LCCPR - Line closes code proving Relay Type: QNl- 8F/8B.
This Relay is specially introduced to effect transmission of answer back Line Closed only if the
enquiry code is Line Closed and not otherwise. It picks up on receipt of line closed code,
picking up of this relay enables the relay TGTR or TCFR to de-latch and sets the Inst, to Line
Closed condition also displays LC indication. Further, it also closes CTR relay circuit along
with RCKR up to enable answer back line closed code transmission. This relay after picking up
remains in that condition till CTR drops while answering back -to complete the transmission of
line closed code or by the release of BCB and LCB buttons.
4.3.19. CAR - Cancellation Relay: Type: QN1- 8F/8B.
Relay is- used for the purpose of cancelling a line clear either before the train leaves a Station or
complete arrival of a train at a Station from where it has left. (In the former case the cancellation
takes a minimum of 120 sees.) This time delay is required to prove that the train for which LSS
is cleared has not entered into the block section with-in this time. This relay picks up by pressing
cancellation button along with BCB button with the Inst, in TGT condition or after the arrival of
a train in TGT-TOL condition. Picking up of this relay closes the 120 sees. Electronic Timer
circuit only on Normal cancellation and also causes the counter to register one higher number
and puts back the LSS to ON if cleared already.
4 3.20. ELECTRONIC TIMER: Q RELAY TYPE.
It is introduced to ensure a time delay of 120 seconds before effecting the cancellation of a Line
clear when the train has not left that Station. Its working is effective only if SNR is in up
condition with BCB & Cancel buttons in pressed position. The lapse of 120 secs, is notified by
Free indication.
4.3.21. ASCR - ADVANCED STARTER CONTROL RELAY. TYPE: QN1- 8F/8B.
Relay is used to control the aspects of Last Stop Signal. It picks up only in TGT condition and
that too on release of Advanced starter control as clearing of LSS is the only authority for a
driver to leave a Station along with his train. Cancellation of line clear before the train leaves a
station-or occupation of FVT in TGT condition causes this Relay to drop resulting LSS to
display its ON aspect. Further, it will not be possible to pick up this Relay again unless a fresh
line clear is obtained and the control on LSS is once again released which is possible only after
complete arrival of a train or cancelling the line clear.

13. 13
Note:- It is customary to prove this relay back contact in SNR circuit with a view to ensure
dropping of this relay after every train. This prevents reappearance of SNR indication if SM puts
back the LSS to normal after clearing the same for one reason or other as this relay will not drop
and hence the circuit of SNR is not getting completed. With a vie eliminate this discrepancy
and to ensure its positive dropping this relay back contact 3 introduced in ASTR initial pick up
circuit. Hence proving of this relay back contact in circuit can be eliminated.
4.3.22. SHKR- SHUNT KEY CHECKING RELAY. TYPE: QN1- 8F/8B.
This Relay is used to prove that shunting key is not extracted from the RKT/ Instrument at the
time of taking Line Clear. Extraction of the shunting key opens this relay circuit as the KEY IN
contact is proved in it. It picks up by pressing BCB with TGB or LCB when the Inst, is in Line
Closed condition or on receipt of 2nd TCF/LC pulse. Picking up of this Relay initiates SCKR
and SNR to pick up. As this Relay is also used to achieve no drain circuit feature, more
conditions are also included in its pick up circuit. Inclusion of LCCPR and CTPR down contacts
in its initial pick up circuit ensures that these relays are assumed to their normal position at the
end of each operational code.
4.3.23. SCKR - SUP/CATCH SIDING CONTROL KEY CHECKING RELAY TYPE:
QN1- 8F/8B.
This Relay is used to prove that slip/ catch siding point control key is not extracted from the
RKT/Inst. at the time of taking line clear. As the slip/ catch siding control KEY IN contact is
proved in this relay circuit, extraction of this key opens its circuit, picking up of this relay closes
SNR circuit.
4.3.24. BCBR - BELL CODE BUTTON RELAYS. TYPE: QN1- 8F/ 8B.
This is used for repeating the BCB switch contacts and picks up whenever bell code button is
pressed if the instrument is not locked. Proving of BCBR up contact in TGTR latch coil circuit
and TCFR de-latch coil circuit ensures the continuous pressing of BCB for setting the
instrument to the respective condition.
4.3.25. TGBR - TRAIN GOING TO BUTTON RELAY. TYPE: QN1- 8F/8B.
This Relay is used for repeating the TGB switch contacts and picks up by pressing TGB button
provided the instrument is not locked. Proving of CTPR relay down contact in its initial circuit
prevents setting of an Inst, to TGT prior to dropping of this relay from the last operation, i.e.
immediately after setting the Inst, to line closed condition. Proving of TGBR up contact in
TGTR latch coil circuit ensures the continuous pressing of TGB for setting the instrument to
TGT condition.
4.3.26. LCBR - LINE CLOSED BUTTON RELAY - TYPE: QN1- 8F/8B.
This relay is used for repeating the LCB switch contacts and picks up whenever Line Closed
button is pressed provided the instrument is not locked Proving of this Relay up contact along
with BCBR up in TCFR de-latch coil circuit ensures continuous pressing of BCB and LCB
switches for setting the Inst, to Line Closed condition.

14. 14
4.4. TIME DELAY UNITS.
The condensers Resistors and diodes etc. required for obtaining the required time delay on
various relays are wired in a printed circuit board and mounted on top of the relay cabinet or
wired conveniently in four Q Relay bases- named as Unit I. Unit II. Unit III and Unit IV The
fourth one is used for fixing diodes and matching resistance for CRR relay. (250 ohms 10 watts)
Particulars of the Relays having the condensers and with units name are mentioned below.
Unit Nos. Relays
I CTR, CTPR, RCKR
II 2 CR, LR, LPR, TOLAR and SHKR
III 1 CR, 3 CR, CAR, PCR and counter
IV ASR, CRR diodes and Bell circuit resistance.
5. POWER SUPPLY ARRANGEMENT
The power supplies used for working this instrument Relays etc. are furnished below.
1. Telephone Circuit 3V Battery OR 24V
[Depending on availability at the location]
2. Local circuit 24 V. Battery
120 AH cells 13 nos. are preferable as minimum 24v. on load
Is required for its reliable working.
3. Line circuit Battery to supply minimum of 60 ma.
Line current
The battery voltage depends on Length of block section
and hence It varies from one section to other section.
4. External circuit 24 v battery
This battery is generally provided at home or adv. starter location in Mechanical signalling
Yards and in case of power signalling, selection battery itself is used.

15. 15
6. GUIDLINES FOR INSTALLATION & MAINTENANCE
Note:- Line Circuit with EARTH RETURN Shall not be used:
6.1. Local Battery voltage at the Instrument terminals on load should not be below 24 volts.
Secondary cells of sufficient capacity may be used as the maximum working current per
Instrument-. about 1.2 Amps.
6.2. The Local battery voltage on load should not exceed a maximum of 29 V as it may affect
the zenar diode working.
6.3. The difference between the local battery voltages of the interconnected instruments on
load should be kept to a maximum of 4 volts, i.e. between 24 V & 29 V.
6.4. The line battery shall be capable of supplying a minimum current of 60 ma on line but
not more than 70 ma.
6.5. The Line current shall be measured both at the transmitting and receiving ends. There
shall not be an appreciable variation.
6.6. Separate line battery should be provided for each instrument. Whenever the line battery -
changed the line current should be checked.
6.7. Where ever dual bank batteries are used for line circuit, the current should be measured
before and after every change over. This is to assess the level of charging required for the
discharged bane— bank.
6.8. While installing these instrument, care shall be taken to ensure that the Relay plug boards
and the Relay contact springs are not damaged, (keep the Relays parallel while
plugging/removing the Relays.)
6.9. Maintain correct polarity while connecting HOOTER leads.
6.10. HMT cord should be connected to the respective terminals to ensure that no current is
drawn from the telephone battery when the HMT button is not pressed.
6.11. Whenever the instrument fails, interchanging of Relays and units shall not be resorted to
without ascertaining the actual cause and this change may be effected only if it is warranted.
6.12. Relays and timer units shall not be left without the Relay retaining clip.
6.13. Whenever the resistance or condensers are replaced in the units correct values have to be
selected and soldered properly
6.14. Oiling of TLB switch contacts shall be avoided.
6.15. During periodical maintenance/Inspection, the charger shall be switched "OFF" and the
working of the Relays has to be observed for few operations. The terminal voltage should also
be monitored during the working in order to ensure the condition of the battery.
6.16. All Instruments should be paired with similar type only.
6.17. All the latch Relays (QLl Relays) should be in de-latched condition while commissioning
equipment.
6.18. Ensure all the removable connectors are locked perfectly in the plug board.

16. 16
INSTRUMENTS WORKING
7. TECHNICAL KNOW-HOW
In push button Tokenless Block Instrument for restoration of failures/ troubles, one should have
a minimum basic working knowledge of this Instrument and its Relays operating Sequence.
Without this, it is practically difficult to restore failures.
i. It works on DC pulses and that are controlled mainly by the Code progressing relays-
1CR, 2CR, and 3CR.
ii. The pulses can be generated either manually/ automatically.
iii. Generally, a pulse will be terminated by the pulse receiving Inst. In case the receiving
Inst, fails to do so, it will be done by the transmitting Instrument itself but after a
predetermined time interval, i.e. by the relay CTR.
iv. Picking up of TOLTR relay Initiates only negative pulse and picking up of PCR relay
initiate only positive pulse.
v. The relay TOLAR will pick up on receipt of 2nd pulse of TCF/ TGT code and NOT in
other codes.
vi. The relay PCR will pick up on complete arrival of train of on cancellation of the line clear
vii. The relay CTPR up Is a must for receiving TGT code.
viii. To set TCF condition, up position of RDR,1CR,P2R, TOLAR and CRR (R) are a must in
additions to SNR.
ix. To set TGT condition, up position of CTPR ,RDR,lCR,N2R, TOLAR, ASR and CRR (N)
Are a must in addition to SNR.
x. The timing circuit of 1CR and CTPR relays play a major in changing the INST,
condition, i.e. LC to TCF/TGT etc.
xi. The release timing characteristics of a relay mainly depends on its condenser charging
Voltage-Local battery voltage and its drop away voltage.
xii. The working of relays TCKR/CRR , is almost Identical and physical observation of these
relays working will give clear picture about the nature of failure and its place.
xiii. The relays SHKR, SCKR and SNR should be in up.
xiv. The relay TAR should be up on arrival of a train.

17. 17
8. TROUBLE SHOOTING METHODS
Failures In this Inst are due to
i. LINE FAULT.
ii. LOW VOLATGE LOCAL/LINE BATTERY
iii. INSTRUMENT CIRCUIT FAULT.
IN TRANSMITTING INSTRUMENT
i. Observe the working of TCKR relay.
Observation Place & Nature of fault
up period Duration is more. Fault is in the Receiving Inst. - RCKR not
picking or SHORT in LINE.
ii. It does not picks means, Line is OPEN.
even after- CTR picks up.
iii. After checking TCKR working ensures correct transmission of functional codes.
TCF :( - + -); TGT: (- - +); TOL: (- - -); LC: (- + +) by observing the working of relays
NTR & PTR.
IN RECEIVING INSTRUMENT
i. Observe the working of the relays CRR(N) & CRR(R)
Observation Place & Nature of Fault
Up period duration Fault is in this Instrument
is more - RCKR not picking up.
Not picking up Fault in the Transmitting Inst, or
in Line - Short / open
LOCAL BATTERY PROBLEMS
i. TOL ack. May not be effective.
ii. Delay in setting the Inst, to TGT.
iii. Answer back Line Closed Code NOT Receiving - LCCPR not sticking at the other end Inst