notes on diado block instrument

CAMTECH/99/S/DAIDO/1.0 1

SINGLE LINE, HANDLE TYPE TOKEN LESS BLOCK INSTRUMENT

(FM CODED)

1. INTRODUCTION

This Hand book covers the general requirements of, Single line, Handle type Token less Block Instrument for use in RE & Non-RE sections.

A pair of Block Instruments is connected electrically through overhead or cable to control the movement of trains on single line Block Section in either direction.

The Instrument is designed to work on Frequency Modulation (Carrier frequency 1800 Hz or 2700 Hz and modulating frequency 65 Hz and 85 Hz).

1.1 Advantages over Token Block Instrument :

1. Less operating time. 2. No Token exchange.3. Less physical strain.4. Problems like token missing, token balancing,

census of token, recoupment of lost token or damaged token etc. are not encountered.

5. Avoidable detention is minimized.6. Increase section capacity

S/ Line Tokenless B/Instrument December’ 1999


7. Maintaining normal polarity/Reverse Polarity of Block instrument is not required.



2. SYSTEM COMPOSITION

The Block instrument is compact & robust in construction and fit to stand for rough handling. It is easy to maintain. Removal/ replacement of any part or sub-assembly does not disturb the adjoining parts/ sub-assemblies.

The following components are provided within the Block Instrument:


TCF

LINE

PB2 PB1

Train On Line Indicator

COUNTER 2

Time Release

Bell

NS1 S2

TGT

Block Handle

GalvoBlock phone

21

SM SH


2.1 Block Handle :

A mechanically operated rotary type handle, called Block Handle is located in the front on the lower part of the Block instrument. Different contact positions of the handle are shown in figure given below:

S/ Line Tokenless B/Instrument December’ 1999FORCE DROP LOCKING ARRANGEMENT(DEVELOPED VIEW)

YIXI

YXN

B

A

VARIOUS POSITION OF BLOCK HANDLE

FORCED DROP PROJECTION

FORCED DROP PROJECTION

LOCK PAWL

L A B X X 1 N Y Y1 D R

L R

D


2.1.1 The handle is free to be turned between X and Y, R and D and also between L and B. Movement of the handle to Train Coming From, Train Going To and back to Normal position from Train Coming From and Train Going To is controlled by an electric lock and this lock is required to be energized at Y position for turning handle to Train Coming From and at D or B position for turning from Train Coming From or Train Going To to Normal. For turning to Train Going To, the lock is initially energised at X position but gets forced dropped before X and is actuated at X position for further movement to Train Going To. The locking effective at X is termed as check locking and is provided to ensure the conscious cooperation of the operator at the other end. This locking is however not effective while turning the handle from Train Going To normal even though the lock is forced dropped. It is because of the beveled edge of the concerned notch on which the lock just slides over and does not cause an obstruction to the movement of the handle.

The block handle assembly consists of 24 sets of spring contacts (circuit controller), actuated during the course of handle of operation.

2.1.2 Need for Forced Drop Arrangement



When the lock gets energised then the handle is free to move from Normal to Train Coming From/Train Going To position depending upon the code that is received. Due to residual magnetism there is a possibility of lock armature to stick up, then the operator can normalise the block handle from Train Coming From/Train Going To. To avoid such type of irregular movement there is a need to lock the handle in respective position. The projection on the locking bracket ensure the forced drop of the lock coil so that the operator can not normalise the block handle, once it is turned to Train Coming From/Train Going To, with out cooperation of other operator.

2.2 Galvo

Indicates incoming and outgoing DC current. The resistance of the coil is 18.2 ohms, working current is 110 mA and working voltage is 2 volt.

2.3 Time release Indication

It is an electromagnetic indicator to indicate the maturity of Time Element Relay during cancellation of a line clear. The coil resistance is 200 ohms.



Normally it shows white indication with words LOCKED and when operated it shows green indication with words FREE.

2.4 TOL Indicator

It is an electromagnetic indicator(magnetic latch type). It operates on entry of train in to block section at either of station.

When the Block section is clear, it displays white indication and when the train enters into the Block Section on a line clear it changes to Red indication with writing “Train On Line” and it holds magnetically. The indicator again changes to white when block handle is turned from any position to line closed.

2.5 Switch S1 with counter

Switch Sl is a two position switch. when operated to reverse it initiates the cancellation of line clear. The counter is used to register cancellation operation.

2.6 Switch S2 with counter

Switch S2 is a two position switch. when operated to reverse it is used for normalising the



instrument during a push-back operation of a train to the starting station.

Push Back operation is performed immediately after reversing S2. The counter is used to register Push Back operation.

2.7. Push Button PB1

It transmits DC current for exchanging bell codes.

When PB1 is pressed alone it transmit

1. DC (-ve) on Line 1 for Bell.2. DC (+ve) on L1 for TOL acknowledgment.3. The same button, when pressed along with

PB2, is used for sending of operational code.

2.8 Push Button PB2

It is used in conjection with PB1 to transmit operational codes to permit the operation of block handle at other station. The code sent is frequency modulated code along with a DC (+ve) code.

PB2 is pressed always along with PB1 to pickup PBPR, which in turn sends ;

i) Frequency modulated code by switching on the Transmitter.



ii) DC (+ve) on L1.

2.9 Single Stroke Bell

It is mounted on the top of the instrument and is used for exchanging bell code signals i.e. It provides to receive bell code. The bell coil is wound to a resistance of 310 ohms and requires about 70 mA for operation.

It sounds when BLR or NR picks up and used for exchanging Bell Code.

2.10 Buzzer

Two electronic buzzers (BZ1 & BZ2) are provided in side the Block instrument.

BZ1 - It is a dual tone buzzer & sounds at both stations when the train enters into the block section and stops after acknowledgment by the pressing PB1 at the train receiving station.

BZ2 - It Sounds at the Receiving station on train arrival on proper reception signals and sequence. It stops by normalizing the Home Signal SM’s slide/lever.

2.11 SM’s Key



To avoid unauthorised operation in the absence of SM.

When this key is taken out the block instrument becomes inoperative for all functions except for:

i) Reception of Bell Code.ii) Reception or transmission of TOL Code.

2.12 Shunting Key

This key is used as a shunting authority to shunt in any direction beyond Last stop signal up to first stop signal of the station. It is normally kept inserted in the Block instrument. It can be taken out only when the block handle is in Line Closed or Train Going To position, and when taken out, the Block handle is locked mechanically in last position. The insertion and extraction of key can be done only when SM’s key is inserted and turned ON.

2.13 Transmitter

It transmits a frequency modulated output (1800 or 2700 with 65 or 85 Hz) when the DC feed is connected to it by different selections. The modulated frequency is selected by the transmitter by an external loop completed through the



relevant selection according to the condition of the block instrument.

2.14 Receiver

This receives the frequency modulated signals transmitted from the other end and gives DC output for energising either CR1 or CR2 depending on the modulating frequency of the code received. The receiver is switched on when the DC feed is connected through the relevant selections.

2.15 The block instruments are designed to work either on 1800 Hz or 2700 Hz carrier frequencies. The modulating frequencies are 85 Hz and 65 Hz and these are common for all the instruments.

The codes used in the Block Instrument are

2.15.1 1800 Hz or 2700 Hz modulated by 85 Hz with DC positive : To permit operation of block handle from line closed to Train Coming From, Train Coming From to line closed and Train Going To to line closed.

2.15.2 1800 Hz or 2700 Hz modulated by 65 Hz with DC positive : To permit operation of block handle from line closed to Train Going To.



2.15.3 1800 Hz or 2700 Hz modulated by 65 Hz : To set the other end’s Block instrument to “Train On Line”.

2.15.4 DC negative : For exchanging bell code signals.

NOTE :

DC positive refers to line battery positive connected to line 1 and negative to line 2.

DC negative refers to line battery negative connected to line 1 and positive to line 2.

3. RELAYS NOMENCLATURES

3.1 BLR

It is a biased Relay and picks up when (+ve) on L2 and (-ve) on L1 is received from the line and the single stroke Bell sounds through the pickup contacts of BLR.

3.2 NR

It is also a biased Relay and pickup when (+ve) on L1 and (-ve) on L2 is received from the line, Single stroke Bell sounds and lock magnet energised through its pickup contact.



3.3 PBPR

Picks up when PB1 & PB2 are pressed simultaneously or only PB1 with TOLR pickup condition during TOL code transmission. It connects DC (+ve) on L1 and (-ve) on L2 and transmitter to the local Battery.

3.4 CR1 : Coding Relay

3.5 CR2 : Coding Relay

3.6 TRSR : Train sending Relay

3.7 1R

It proves the normal condition of reception signal’s and Last stop signal’s levers and SM’s slide.

3.8 1TPR

This is a repeater of FVT Track Relay (ASTR).

3.9 TOLR : Train on line relay

3.10 2R

Picks up after the complete arrival of the train with proper sequence.



3.11 3R : Cancellation Relay

When S1 is turned for normal cancellation, after a specified time (120 sec.) delay it picks up and the ‘FREE’ indicator energised through its pick up.

3.12 TEPR

Once S1 is turned for normal cancellation the electronic timer relay gives output of 24 v after a specified time delay (120 sec.) which in turns picks up the TEPR.

3.13 Timer Relay

It is an electronic Type Relay used for pickup of TEPR relay after 120 sec. time delay in case of normal cancellation.

3.14 TELR

Telephone Relay of resistance 70 ohms, picks up when switch of hand micro telephone is pressed and in turns it connects the telephone on line and also disconnect the TX & RX from the frequency line.

3.15 External Relays :

3.15.1 ASR : Advance Starter Relay



3.15.2 HSR : Home Signal Control relay.

3.15.3 TAR : Train Arrival Relay

3.15.4 SNR : Signal Normal Relay

4. POWER SUPPLY

Three sets of batteries are required :

4.1. Line Battery

Line battery is normally of dry cells. The voltage is varying from 24 V depending on the length of the block section in order to get a working current of 100 mA on line. This battery is connected on line whenever the DC is required to be sent either foe exchanging the bell signals or as a part of the operational code.

4.2. Local Battery

Local battery is of 24 Volt and is used for giving the supply to the transmitter and receiver and also operating relays, indicators, local magnets etc. of the instruments. Since the current drain on the battery is high, secondary cells are generally used.

4.3 Location/External Battery



It is used for external circuits to repeat the external conditions to the instruments according to the requirements of the circuits. Picking up of PBPR, connects +ve to L1 & -ve to L2 and also switches on the DC feed for the transmitter. Since the block handle is in normal position, the loop circuit is connected for the modulated output is connected to the line.

5. SPECIAL FEATURES

5.1 Special features of Daido Tokenless Block Instrument are given below:

5.1.1 To ensure that the relays “NR” and “BLR” are not picked up simultaneously back contact of NR relay is proved in BLR circuit. Similarly in the PBPR circuit back contact of CR1 and CR2 relays have been provided to ensure that PBPR relay will not be energized. While receiving modulated frequencies.

5.1.2 Front contact of PBPR Relay has been proved in the DC feed circuit of transmitter, whereas back contact has been proved to the receiver circuit to guard against receiving its own F.M. output modulated frequency transmitted similarly, back contact of CR2 and CR2 relays have been proved in the DC feed circuit for transmitted to ensure



that no code except the code of bell signals can be generated unless the code relays are de-energised.

5.1.3 Since TOL code has to be transmitted automatically as soon as a train occupies FVT, Front contact of PBPR Relay is not proved in DC feed circuit to the transmitter but the same is taken in TOLR Front contact NR Relay back contact with the block handle at L position.

5.1.4 Similarly for the receiver to be in readiness. To receive the TOL code, the DC feed circuit is taken via 2R Relay back contact with the block handle “R” position.

5.1.5 Pressed contact of the PB2 button in the DC feed circuit of the transmitter, proves the positive action taken to energise PBPR Relay for transmitting modulated frequency along with DC.

5.1.6 Block handle contacts (BX) and (DY) are included in the DC feed circuit to the receiver so that the DC feed to the receiver is switched on only. When the Block handle operation is initiated. Thus minimising battery consumption.

5.1.7 SM’s key contact has not been provided in the DC feed circuit of Transmitter for transmitting and receiving of automatic TOL code to ensure that the TOL indicator will display, immediately the



block sections occupied irrespective of the position of the SM’s key.

5.1.8 To ensure that the relay CR1 and CR2 are not be energised one at a time, back contact of CR1 relay is proved to energise CR2 relay and similarly back contact of CR2 relay is proved to energise CR1 relay.

5.1.9 Cross protection to the lock Magnet is given through the CR1 and CR2 back contacts.



5.1.10 “Transmitter” and “Receiver” are connected to line through the back contact of TELR relay is ensure that during conversation on telephone, no code is transmitted or received by the transmitter and receiver respectively at either end. Similarly the telephone set is connected to the lines through the front contact of TELR Relay and TELR Relay feed is taken through the back contact of CR1 and CR2 relays to ensure that during Transmission and reception of Code the telephone is disconnected the back contact of TOLR is included in the TELR PICK UP circuit to ensure that the telephone circuit is disconnected the moment TOLR picks up to transmit TOL Code.

5.1.11 TOLR relay is made slow to release since its energising circuit is through the front contact of TRSR released stick circuit as through the back contact of TRSR relay.

5.2 POSITION OF RELAYS IN RELAY RACK

T E P R C R 1 C R 2P B P R B L R N RT O L R T R S R I T P RI R 2 R 3 R



5.3 DIFFERENT COLOUR CODE FOR INTERNAL WIRING

COLOUR DESCRIPTION

RED - Local Source (+)BLUE - Local Source (-)BLACK - Block Line CircuitBROWN - Relays circuit for Reverser ControlYELLOW - Transmitter and Receiver circuitGREEN - Relays and Lock magnet circuitWHITE - Other circuit

6. CIRCUIT DESCRIPTIONS

6.1 NORMAL POSITION :

Normally, the Block handle is in center upright position, i.e. ‘Line Closed’ position. The SM Key is IN, shunting (SH) key is IN, cancellation switch (S1) and push back switch (S2) are in normal position. The TOL and time release indicator are white and the Galvo indicator indicates zero current position. In this case, all the relays except for ITPR and 1R are dropping away, with no current flowing in the block line and the concerned signals and levers are in normal position (Fig. 1).


10TPPR 5 15 1+ 2- 55 45 10TPPR


6.2 When a train is leaving A Station to B Station.

6.2.1 Turning the SM key to ON position at Station A completes a circuit. Push Button PB1 is pressed to give CALL ATTENTION Bell code signal to B station. A DC (-ve) current flows to B station in Line 1, to pick up the BLR at B station as per fig. 2 and fig. 3.


1R

N1 24VB1 24V

N N N

FIGURE 1

1 2

N1 24VB1 24 V

1TPR

2 1

BTPR 10NBPR 3 4 10 10LCC 1+ 2- 56 46

6 16

1 2

35 25

36 26

2 12 67 68 CHI SM PPB1 NR PBPR

N2 3 13 1 R2 2 PB1 PB2 PBPR L1 (-)

L2 (+)

OUTGOING CIRCUIT AT A

20 OHM/2W2

4 UF/160V

FIGURE 2

B2

2 3

6A 5A 6D 2/5D

3


Now with the BLR picking up, a current flows to ring the BELL as per fig. 4.


61 62 48 58 555858

2A 1A 1 2

N24V

B24V 224V24V

LOCAL CIRCUIT AT B

BELL

FIGURE 4

BLR

21

31

BLR

4 UF/160V

1 2 35 25

36 26PBPR PB2 PB1 2- 1+ D2 26 PB1 NR PBPR

L2

L1

INCOMMING CIRCUIT AT B

BH-1264/7B 8B 3 2 6A 5A 6D 2/5D

FIGURE 3

3

4


6.2.2 Upon receipt of a call attention at B station, SM inserts & turns SM key to IN. SM presses to acknowledge call attention signal from Stn. A. The circuit is same as described in Fig. 4 above.

6.2.3 Verbal communication for grant of Line Clear takes place between SM of Stn. A and Stn. B over block telephone.

6.2.4 Push Button PB1 and PB2 are pressed simultaneously at Stn. A to send the IS LINE CLEAR code. PBPR relay picks up as per fig. 5.

6.2.5 With the PBPR picking up at A the NR picks up at B station through the line circuit as per fig. 6 & 8.


PBPR

21

B24V 61 62 SM CR1 PB1 PB2 CR2 1R NR N24V

7D 8D 2B 1B 8B 4/7B

OUTGOING CIRCUIT AT ‘A’

36 26

B2 2 12 67 68 CH1 PBPR 35 25

N2 3 13 1 R2 2 PPBPR

20 OHM/2W 1D 2/5D

L2

L1

FIGURE 6

FIGURE 5

LOCAL CIRCUIT AT ‘A’



B 24 V 61 62 48 SM 1R PBPR PB2 TOLR CR1

4A 3A 4/7 D 3D 6A 2/5A 5D 6D 5D 6D

TO ISOLATION TRANSFORMERLINE SIDE

3 4

5

6 1 27

158

N

131

21TX

34

37

FIGURE 7

N243

R3 / 470 ohm 2 watt

-2 +1 D1 18 8 PBPR 35 25

PBPR 36 26

8B 4/7 BNR

XYLBRD

BY-126

6D 2/5 D

FIGURE 8

L1

L2


6.2.6 An FM code is generated due to picking up of PBPR at ‘A’, which connects power to TX as per circuit in Fig. 7. The modulating frequency F1(85 Hz) is selected over terminal TX-5 & TX-6 & modulated current flows to terminals 34, 37 to the line side isolation transformer ( in this case the input circuit to RX of same station is isolated by PBPR back contacts.

6.2.7 CR1 picks up at Stn. B on receipt of modulated current as per fig. 9.


B24 V 61 62 48 SM 1R PBPR TOLR 41 42

4A 3A 4/7 D 8D 5D 6D

TO ISOLATE TRANSFORMER (LINE SIDE)

3 4

7

1 25

15831

21TX

PBPR CR2

TELR

BXDY

7A 8A

5B 6B

CR1

CR2 1+

FIGURE 9

N24


6.2.8 On getting the Bell & Galvo deflection at Stn. B, SM turns the block handle as far as Y point, Lock magnet picks up to releases the Block Handle, which can be turned to right position (Train Coming From position), as per fig. 11.

S/ Line Tokenless B/Instrument December’ 19992/5A 6A

31

N 24V

R1

BXDY

48

58

61 62S1 N1 S2 N1 TEPR TRSRT CR1

21

CR1

B 24V SM

5D 6D 4/7B 8B 1A 8/5AR2

M4/7B 3B

NR 2 1

FIGURE 11

61 62 48 58 NR

4A 3A 1 2

N24V

B 24V

LOCAL CIRCUIT AT ‘B’

31

21

BELL

FIGURE 10


6.2.9 While the block handle is being turned from one to another position, the circuit controller contact (XY-RD-LB) of the handle in line circuit, in series with the relay NR is opened between the Y&D points.



6.2.10 On opening of circuit controller contact in Line circuit, a resistance R3 to be added in series to line circuit with a resultant reduction in the volume of line current ( which remains substantially greater than the drop away current of NR). This cause a click on Galvo needle at both stations, making it possible for SM of button pressing station to know that the block handle has been turned. Then PB1 and PB2 at station A may be released (The same procedure is followed in operating the handle as subsequently to be described).

6.2.11 After confirming that the Galvo needle has returned to zero position (indicating that A station has stopped sending a code of signal), PB1 and PB2 are now simultaneously pressed down at B station to send a code of signal to A station (Fig. II). PBPR relay picks up as per


XYLBRD 6D 2/5 D

R3 (470 Ohm)

PBPR


fig. 5. With the PBPR picking up at A the NR picks up at B station through the line circuit as per fig. 6 & 8.

6.2.12 An FM code is generated due to picking up of PBPR at ‘A’, which connects power to TX as per circuit in Fig. 7. The modulating frequency F2(65 Hz) is selected over terminal TX-5 & TX-7 & modulated current flows to terminals 34, 37 to the line side isolation transformer

Local and outgoing circuit at ‘A’ (Fig. 12,13 & 14) local and incoming circuit at ‘B’ (Fig. 15 to 16).


LOCAL AND OUTGOING CIRCUITS AT B

B24V 61 62 SM K CR1 PB1 PB2 CR2 1R NR

PBPR

21

7D 8D 2B 1B

8B 4/7B

FIGURE 12

N24 V



B2 2 12 67 68 CH1 PBPR 35 25

3B 4/7B

20 OHM/2W 1D 2/5D

36 26N2 3 13 R2 PPBPR

L2 -

L1 +

FIGURE 13

4A 3A 4/7 D 3D 6A 2/5A 5D 6D 5D 6D

TO LINE SIDE TRANS

3 4

5

6 1 27

158

R

1 31

21TX

34

37 5 6 2R

B24 V 61 62 48 SM k 1R PBPR PB2 TOLR CR1 CR2

TELR

2/5D 6D

4 1

FIGURE 14

N24



R3

18 8 1 35 25 L1

PBPR 36 26 L2

8B 4/7 BNR

XYLBRD

BY-126

6D 2/5 D

470 OHM/2W

‘X’

FIGURE 16

31

61 62 48 58 NR

4A 3A

N24V

B 24V21

BELL

FIGURE 17

37

B 24 V 61 62 48 SM k 1R PBPR TOLR 41 42

4A 3A 4/7 D 8D 5D 6D

TO LINE SIDE I.TRANS

3 4

78

5 2

6

58

PBPR CR

TELR

BXDY

7A 8A

5B 6B

CR2

CR2 1+ 2-4 1

34

7B 8B

LOCAL AND INCOMING CIRCUITS AT `A’

N24

FIGURE 15

RX

21

31


6.2.13 On getting the Bell & Galvo deflection at Stn. B, SM turns the block handle from N point to as far as the X point. At X point TRSR picks up & releases the lock on block handle by picking up lock magnet as per fig. 17 & 18. TRSR remains UP till X/ and later on sticks through its own front contact in LX/ position of Block handle. The lock magnet is once again required to be in picked up condition to release the block handle at check lock position at X/as per fig. 18 &19.


B24

31

21

TRSR ITPR 37 38

R1 C1 1000 UF/60V

61 62 48 58 3R CR2 NR ITPR 39 40

N24

2/5 D 1D 2/5A 2A

TRSR

1+ 2-

7B 8B

FIGURE 18

LX/

XX/

31

61 62 48 58 NR

4A 3A

N24V

B 24V21

BELL

FIGURE 17


6.2.14 When Block handle is in Train Going To position, i.e., Line clear is granted, Last stop signal can be taken OFF by reversing the necessary controls like SM control on signal, Lever/ switch/ push button operation etc. Reversing of any of above control causes 1R to drop. An external relay ASR (Advance starter control relay) picks up as per fig. 20. With ASR picking up, it possible to take OFF the Last Stop signal.


B3 24V 65 66 1R 2R TRSR S1 17 18 53 43 HSR

8B 4/7 B N312V

7D 6D ASR

R3FIGURE 20

N3

48

58

S1 S2 TRSR 2R 3R CR1 9 10 1 2 NRB 24V SM 1R

N 5D 6D 4/7B 5B 6B 7A 8A 1A 2/5A

21

31

3B 4BXX

M

CR2

6A 2/5A

N24

2A 1A

FIGURE 19


6.2.15 Now the train can be sent into block section. On entry of train into block section, FVT track relay drops causing 1TPR to drop, thus releasing the stick circuit of TRSR to drop. Dropping of the TRSR causes the ASR to drop and replace the Last Stop signal to ON automatically.

6.2.16 With the 1TPR drop, the circuit of TRSR breaks , which drops with a time lag, but before its dropping, TOLR picks up as per fig. 21 through Path 1.

When TRSR drops after the time lag, TOLR sticks through Path 2. the indicator TOLK and buzzer BZ1 are actuated through a branch of a contact LB, indicating a train departure (TOL). An additional Path 3 is provided to prevent the premature dropping of TOLR during transition, when other station is transmitting TGT code & at the same time TOLR picks up. It ensures that TOLR will not drop before transmission of TOL code.A Normal contact of S2 switch is provided in the stick circuit to stop the transmission of TOL code, during a failure of its transmission or acknowledgment to silence the departure buzzer.

6.2.17 At this time the advance starter lever is restored to normal position.


B24 61 62

31

21 TRSR ITPR 13 14

CR2 NR 23 24

N24

XX’YY’

LB

2/5 D 6D 7D 8D

TOLR

1+ 2-

7B 8B

D3 BY-126LB

BZ1

2B 1B 2/5B 1B

N3R3

TOLR S2

3R48

58

TRSR NR

4B 3B

5

FIGURE 21

Path1

Path2

Path3

TOLK


6.2.18 An FM code is generated due to picking up of TOLR at ‘A’, which connects power to TX as per circuit in Fig. 22. The modulating frequency F2(65 Hz) is selected over terminal TX-5 & TX-7 & modulated current flows to terminals 34, 37 to the line side isolation transformer ( in this case the input circuit to RX of same station is isolated by TOLR back contacts.

6.2.19 CR2 picks up at Stn. B on receipt of modulated code F2. The power to RX is connected through B24-fuse (61-62)- Terminals (48-58)-2R(B)-R.


2/5D 6D 1A 2/ 5A 5D 6D 5D 6D

LINE SIDE I. TRANS

3 4

5 (c)6 1 27

L43

L

31

21

TX

34

37

6D 5D 3A 4/7

B24 V 61 62 48 SM

TELR 313R TOLR 4 3

44 NR TOLR CR1 CR2

4

1

N24

FIGURE 22

58


TOLR picks up as per fig. 24. With the TOLK and BZ1 operating through the same circuit as in A station to give an indication of train departure. Local and incoming circuit at ‘B’ (Fig. 23).


37

B 24 V 61 62 48

TO LINE - SIDE I.TANS

3 47

8

5 26

58

31

21

RX

PBPR CR2

TELR

7A 8A

5B 6B

CR2

CR1

RN24 V

2R 45 46

7A 8A

7B 8B

4 1

34

FIGURE 23


6.2.20 SM of Stn. B, on getting TOL buzzer, presses push button PB1 to acknowledge the TOL code. PBPR at picks up as per fig. 5.

6.2.21 With the PBPR picking up, the NR picks up at Stn. B station through the line circuit as per fig. 6 & 8. Picking up of NR causes TOLR to drop & stop the buzzer. As the TOLK is a magnetic stick type, it maintains its TOL indication. (Refer Path 2 in fig. 21)

6.2.22 Dropping of TOLR at Stn. A, stops TOL code transmission by disconnecting power to TX. As the TOLK is a magnetic stick type, it maintains its TOL indication.



6.2.23 CR2 drops at Stn. B & stops the buzzer .


B24 61 62

61 62 42 SM CR1 PB1 PB2TOLR 19 20

PBPR1 2

1

RD

2A 1A

PBPR

21

31

B24

NR

6B 4/7B

7D 8D

FIGURE 25

B24 61 62

31

21 CR2 NR 11 12

N24

XX’YY’

RD

2/5 D 6D 7D 8D 4B 3B

TOLR

.01 UF/100 V

7B 8B

D3 BY-126

BZ1N3R3

TOLR S2

3R

48

58

TRSR NR

2B 1B 2/5B 6B

TOLR

1+ 2-

47 48

1 2

7A 8A 470 OHM/2W

R5

220 OHM/2W

FIGURE 24

N3 12

7D 6D

HSR

ASR

B3 12V 65 66 1R 2R TRSR S1 N4 35 36 54 44

XYRD

LA

2

7D 8D 4/7D 8D

R4

FIGURE 26


6.2.24 A bell code for train departure is issued from A station and a answering signal is issued from B station. After departure of train bell code is exchanged.

6.2.25 At Stn. B, Reception signals are taken OFF. As soon as any of the control pertaining to reception signal is disturbed from its Normal position, 1R drops. Where SM’s control is not provided on reception signals, 1R back contact, in HSR and ASR circuit, is looped in instrument. The HSR picks up (Fig. 26). The home operates in the same way as advance starter.



6.2.26 On arrival of train at Stn. B, AT & BT tracks operate & sense the direction of travel of train. 2R picks up (Fig. 27) & sticks over LX/-RY. With the relay 2R picking up the HSR drops away and the home signal is automatically restored to normal position. At the same time a Buzzer BZ2 sounds to announce the train arrival. The buzzer can be stopped by restoring the SM slide or Home signal controls to their Normal position as per fig. 27.


XX’ Y’

B24 61 62 48 52 7 17 TAR 15 16 21 N24

2R

TAR

R

R

4

R

OUTER 2

2R

BZ2

31

HOME SM 3 4 SLIDE

2B 1B

R

FIGURE 27


6.2.27 Stn. B verifies the e complete arrival of train & sends Train Out Of Section signal to Stn. A. who in turn replies to Stn. B by similar signal. Stn. B presses PB1 and PB2 simultaneously to transmit Line closed code (F1). PBPR picks up at ‘B’ station. ( see Fig. 5).

6.2.28 An FM code is generated due to picking up of PBPR at Stn. B, which connects power to TX as per circuit in Fig. 7. The modulating frequency F1(85 Hz) is selected over terminal TX-5 & TX-6 & modulated current flows to terminals 34, 37 to the line side isolation transformer.

6.2.29 With the PBPR picking up at Stn. B the NR picks up at Stn. A through the line circuit as per fig. 6 & 8. CR1 picks up at Stn. A on receipt of modulated current as per fig. 9.




2/5D 6D 1A 2/ 5A 5D 6D 5D 6D

TO I. TRANS

3 4

5 (c)

6 2

1

43 31

3A 4A TX

34

37

B 24 42 SM

TELR

2/5D 6D

44 NR TOLR CR1 CR2

4 1

N24

R

21

1R

2R

FIGURE 28

TO TRANS

3 4

7 1 28

31

41

RX

7B AB

24 V 61 62 48 SM 1R PBPR TOLR

TELR

4

TOLR

BXDY

4A 3A 4 2D 5D 6D 41

CR1

CR2

4258 1

5B 6B

CR2

FIGURE 29



48

58

S1 N1 S2 N2 TEPR TRSR CR1 7 8 2 NR 21 2 NR

B 24V

N 5D 6D 4/7B 5B 6B 7A 8A 1A 2/5A

21

31

5B 4/7BBDY M

CR1

6A

N24

2A 1A61 62

SM 1R

XX’YY’

TOLK220 OHM/2W

R51 247 48

FIGURE 31

FIGURE 30


With the NR and CR1 picking up Lock magnet is energised at B point of block handle as per fig. 30, making it possible to restore the handle to Line Closed position. TOLK release coil is energised to restore it Normal as per fig. 31.

6.2.30 SM at Stn. A presses PB1 and PB2 simultaneously to transmit Line closed code (F1). PBPR picks up at Stn. A as per fig. 5.

6.2.31 An FM code is generated due to picking up of PBPR at Stn. A, which connects power to TX as per circuit in Fig. 7. The modulating frequency F1(85 Hz) is selected over terminal TX-5 & TX-6 & modulated current flows to terminals 34, 37 to the line side isolation transformer.

6.2.32 With the PBPR picking up at Stn. A, NR picks up at Stn. B through the line circuit as per fig. 6 & 8. CR1 picks up at Stn. B on receipt of modulated current as per fig. 9.

With the NR and CR1 picking up Lock magnet is energised at B point of block handle as per fig. 30, making it possible to restore the handle to Line Closed position. TOLK release coil is energised to restore it Normal as per fig. 31.



The same procedure is followed when a train leaves B station from A station.



6.3 CANCELLATION OF “LINE CLEAR” BEFORE A TRAIN ENTERS THE BLOCK SECTION :

6.3.1 When a line clear has been taken by Stn. A, i.e., Block Handle in Train Going To, & it becomes necessary to cancel the Line Clear, the cancellation switch S1 is put to reverse position at Stn. The following sequence is observed:

External relay ASR drops S1 counter increments to next higher number. All controls are to be replaced to Normal so as

to pick up 1R Timer relay times up as per fig. 32 On expiry of 120 seconds TEPR picks up TEK appears Green with wording “FREE” 3R picks up.

An advice for cancellation of Line clear is sent By SM at Stn. A to SM of Stn. B


6.3.3 An FM code is generated due to picking up of PBPR at Stn. A, which connects power to TX as per circuit in Fig. 7. The modulating frequency F1(85 Hz) is selected over terminal TX-5 & TX-6



& modulated current flows to terminals 34, 37 to the line side isolation transformer.

6.3.4 With the PBPR picking up at Stn. A, NR picks up at Stn. B through the line circuit as per fig. 6 & 8. CR1 picks up at Stn. B on receipt of modulated current as per fig. 9.

With the NR and CR1 picking up Lock magnet is energised at D point of block handle as per fig. 30, making it possible to restore the handle to Line Closed position.

6.3.5 Similarly Stn. B takes action to bring the instrument of Stn. A to Line Closed. SM at Stn. B presses PB1 and PB2 simultaneously to transmit Line closed code (F1). PBPR picks up at Stn. B as per fig. 5.

An FM code is generated due to picking up of PBPR at Stn. B, which connects power to TX as per circuit in Fig. 7. The modulating frequency F1(85 Hz) is selected over terminal TX-5 & TX-6 & modulated current flows to terminals 34, 37 to the line side isolation transformer.

6.3.6 With the PBPR picking up at Stn. B, NR picks up at Stn. A through the line circuit as per fig. 6 & 8. CR1 picks up at Stn. A on receipt of modulated current as per fig. 9.


4A 4B3R

58

B 24V

TRSR 3R

30

2A 1A61 62

1 2

S1

N24

3R LX

29

48 38

2B 1B

TEPR

1 S1 2

R1

COUNTER2A 1A 7D 8D

COM

TEK

TEPR

TIMER

INPUT OUTPUT

N2SM 1R S1

3R

2A 1A

TER1

FIGURE 32


With the NR and CR1 picking up Lock magnet is energised at B point of block handle as per fig. 30, making it possible to restore the handle to Line Closed position. When Stn A turns block handle to Line Closed, TEK changes to White.



6.4 PUSH BACK OPERATION :

When a train sent from Stn. A to Stn. B has entered the Block section, but due to unavoidable circumstances, it has to be pushed back to departure Stn. A, it is called PUSH BACK OPERATION .

6.4.1 The block handle at Stn. A and Stn. B are in left position (Train Going To) and right position (Train Coming From) respectively. TOL indicator indicates that train in to block section.

6.4.2 SM at Stn. A push back switch S2 to reverse position, actuates the counter S2 as per fig. 34. Reception signals are taken OFF. As soon as any of the control pertaining to reception signal is disturbed from its Normal position, 1R drops. HSR picks up as per fig. 26.


4/7A 8A 2/5A 1A TO I. TRANS

FIGURE 33

58

B 24V

61 62

IR PBPR PB2 TOLR CR1

4A 3A 4/7D 3D 1 6A 2/ 5A 5D 6D

3 4

5 (c)

6 2

43 SM

31

TX

34

37

TELR

4

1

N24

L

21

TOLR 3R


6.4.3 On arrival of train at Stn. B, AT & BT tracks operate & sense the direction of travel of train. 2R picks up (Fig. 27) & sticks over LX/-RY. With the relay 2R picking up the HSR drops away and the home signal is automatically restored to normal position. At the same time a Buzzer BZ2 sounds to announce the train arrival. The buzzer can be stopped by restoring the SM slide or Home signal controls to their Normal position as per fig. 27.

6.4.4 Stn. A verifies the complete arrival of train. An advice for push back operation is sent By SM at Stn. A to SM of Stn. B


6.4.6 An FM code is generated due to picking up of PBPR at Stn. A, which connects power to TX as per circuit in Fig. 7. The modulating frequency F1(85 Hz) is selected over terminal TX-5 & TX-6 & modulated current flows to terminals 34, 37 to the line side isolation transformer.

6.4.7 With the PBPR picking up at Stn. A, NR picks up at Stn. B through the line circuit as per fig. 6 & 8.



CR1 picks up at Stn. B on receipt of modulated current as per fig. 9.

With the NR and CR1 picking up Lock magnet is energised at D point of block handle as per fig. 30, making it possible to restore the handle to Line Closed position. TOL indicator changes to White during turning of handle from Train Coming From to Line Closed.

6.4.8 Similarly Stn. B takes action to bring the instrument of Stn. A to Line Closed. SM at Stn. B presses PB1 and PB2 simultaneously to transmit Line closed code (F1). PBPR picks up at Stn. B as per fig. 5.

An FM code is generated due to picking up of PBPR at Stn. B, which connects power to TX as per circuit in Fig. 7. The modulating frequency F1(85 Hz) is selected over terminal TX-5 & TX-6 & modulated current flows to terminals 34, 37 to the line side isolation transformer.

6.4.9 With the PBPR picking up at Stn. B, NR picks up at Stn. A through the line circuit as per fig. 6 & 8. CR1 picks up at Stn. A on receipt of modulated current as per fig. 9.

With the NR and CR1 picking up Lock magnet is energised at B point of block handle as per fig. 30,



making it possible to restore the handle to Line Closed position. TOL indicator changes to White during turning of handle from Train Coming From to Line Closed.


B24 61 62

1

COUNTERLX’

58

48 SM S2

N2

1 S2 2 29 30 21

31

C2R2

N24

FIGURE 34


(D) WHEN A TRAIN SHUNTING (AT ‘A’ STATION)

The Block handles are in Line Closed position at both stations ‘A’ & ‘B’, or Stn. A in Train Going To & Stn. B in Train Coming From.

A station calls ‘B’ station to obtain authorization over the telephone.

SM at Stn. A inserts SM key & turns IN. SHUNT key is taken out & handed over to the driver of a shunting train. The Block handle is locked at the time. The SM key is taken out.

On completion of shunting operation, Shunt key is taken back from driver of train. SM inserts SM


4/7A 8A 2/5A 6A 1A 2ATO I. TRANS

FIGURE 35

58

B 24V

61 62

IR PBPR PB2

4A 3A 4/7D 3D

3 4

5 (c)

6 2

48 SM

31

34

37

TELR

4

1

N24

L

21

TOLR 3R 2R

TX

1 1

6A 2/3A 5D 6D 5D 6D

TOLR CR1 CR2


key & turns to IN, thereafter inserts SHUNT key and turns IN. The advice is sent to Stn. B over the telephone to that effect.

(E) TELEPHONE CIRCUIT :

While modulated current F1 to F2 is being transmitted or received, telephone circuit is isolated from power line.

While telephone is used, transmitter and receiver are isolated from line. To explain in detail telephone relay TELR is inserted in series connection with relay. CR1 (B) CR2(B) and TOLR (B) in the circuit fig. 36. Also TELR(F) is connected in series in the telephone circuit, Thus telephone circuit is isolated from signal circuit. Where modulated current is transmitted and received by TELR which is inserted between signal circuit and Transmitter/Receiver, Transmitter/Receiver is isolated form signal line which telephone is used.



7. TRANSMITTER AND RECEIVER

7.1 Operating Parameters

Transmitter

Item Rating ToleranceTransmitting frequency 1800 Hz or 2700 Hz + 2%Transmitting output 1 mW, 3 mW, 5 mW,

adjustable+10%, -5%

Output impedance 600 Ohms, 1120 Ohms adjustable

+ 2%

Modulation system Frequency modulationModulation frequency 65 Hz or 85 Hz + 1.5 HzPower consumption 1.2 watts or less at 24 V DCInput power supply 24 V DC + 20%Shift frequency 160 Hz + 15%

Receiver

Item Rating ToleranceReceiving frequency 1800 Hz or 2700 Hz +2%Level range 0 to 28 dB In step of 2

dB or lessMax. noise allowance -44 dBm + 2%Input impedance 600 ohms, 1120

ohms adjustableRelay output voltage 24V DC or above 21V min.Power consumption 8 watt or less at 24 V DCInput power supply 24V DC + 20%



Sense level for receiving less than - 29 dBmNo Sense level for receiving

More than - 38 dBm

Shift frequency 160 Hz. + 15 %

7.2 Connection Terminals & Test Blocks

7.2.1 Transmitter

Connection Terminals

It have 8 fixed terminals. Serial Nos. and connections are as below:

Terminal Nos. Connections1 & 2 Out put3 Positive DC input4 Negative DC input5 Common6 85 Hz.7 65 Hz.8 Spare

Test Blocks

Test blocks are provided at the back side of the transmitter with a cover and seating arrangements.



1. 24V DC supply2. Regulated voltage3. Modulated frequency 65 Hz & 85 Hz4. Carrier frequency 1800 Hz. or 2700 Hz.5. TX output

7.2.2 Receiver

Connection Terminals

It have 8 fixed terminals. Serial Nos. and connections are as below:

Terminals Connections1 & 2 Input3 Positive DC input4 Negative DC input5 & 6 Output for CR2 relay7 & 8 Output for CR1 relay

Test Blocks

Test blocks are provided at the back side of the receiver with a cover and seating arrangements.



1. 24V DC supply2. Regulated DC supply3. Input4. Demodulated Signal5. Input to CR16. Input to CR2

7.3 Trouble Shooting Method for Transmitter & Receiver

Sr. SYMPTOM ACTION TO BE TAKEN1. No output from

receiver.Check if the supply is OK by pressing push to make switch in transmitter and receiver. If power ON indicators are glowing with red LED it means power supply is OK. If the red LED does not glow, check the fuse. If the fuses are missing/blown, replace it.

2 Power OK, LEDs OK but relay does not pick up.

Press the PTM switch which is on the front panel and see if the level indicator green LED glows or not. If glows that means relay driving signal is OK & the problem is with



respective relay, so replace it and get the desired result.

If the level indicator Amber LED glows:

The relay driving signal is missing, check the following:

Input to the RX between 5&6 (+10V to +13V PP) between 7&8 (+1.5V to + 2.5V PP), between 9&10 or 11&12 (+21.6V to +26V PP).If the above voltage signals are not regular/proper, open the cabinet and follow the signal flow and check the voltages.

8. EARTHING

A separate earth should be provided for each block instrument.

The resistance of earth shall not exceed 10 Ohm.

The earth shall be located on lower level soft ground far from underground cable, water and gas pipes.



9. SAFETY CHECK

Ensure that double lock is provided and seal is intact.

Try to operate the instrument without cooperation i.e. without receipt of functional code, it shall not be possible to turn the block handle from Line Closed to Train Going To or Train Coming From position.

On receipt of TGT code, turn block handle from Line Closed towards Train Going to & stop midway. Disconnect Line & try to turn the handle further. It shall lock in check lock position. Ensure armature of electric lock on block handle is force dropped in check lock notch and the block handle can not be turned to Train Going to position.

With a train in Block Section, try to bring the block handle to Line closed with & without cooperation from other station, it shall not be possible to turn the block handle to line closed position. The Block handle should remain locked in last operated position.



For Last Stop Signal :

Try to take OFF the Last Stop Signal without taking line clear (“L” position of block handle), the signal should not clear.

Shunt the FVT track, the Last Stop Signal shall go back to danger automatically.

It is not possible to take OFF the Last Stop Signal again unless a fresh line clear is obtained.

SUGGESTION :

a) Removal of Filter unit & X, Y relays in RE area.

b) Disconnect the two condensers of the Block Filter unit

c) The rare gas lightning arrestor should be replaced with MOVR.



10. MAINTENANCE 10.1 Periodicity of Overhauling

A thorough periodical overhauling in Workshop is necessary and the period shall not exceed 7 years.

10.2 Maintenance

The following points are to be kept in mind while doing maintenance for reliable working of block instrument.

The 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 is about 2 Amps ( when thermal time element relay is used) & 0.6 Amp (when Electronic time element relay is used)

The upper limit of local battery on load should not exceed 29 V as it may affect the Zener diode working.



The line battery shall be capable of circulate 110 mA in Line circuit measured at code receiving station.

The line current shall be measured both at the transmitting end and the receiving end. There shall not be an appreciable variation.

Separate battery or DC-DC converter shall be provided for line circuit of each block instrument. Whenever the line battery/ DC-DC converter is changed, the line current should be checked.

??Whenever old type condenser units are changed ( with 4 BA fixing screw ), ensure that the other interconnected instrument condenser unit is also changed to the same type since the values are different.

Care shall be taken to ensure that the relay jack boards and relays are clean and dust free.

During the periodical Maintenance/ Inspection, the charger shall be switched “OFF ” and the working of the relays shall be observed for few operations. The terminal voltage should be monitored during the code transmission in order to ensure the condition of the battery.

Whenever the instrument fails, interchanging of relays and units shall not be restored to, without



ascertaining the actual cause and this change may be effected only if it is warranted.

While plugging in relays/ units, excessive force should not be exerted as it may affect the jack board clips.

11. TROUBLE SHOOTING

Sr.no.

Fault Condition

Cause/ Rectification

1. Bell beats failed from Stn. ’A’ to Stn. B

1. Line battery low or disconnection at station ‘A’.

2. PB1 push button contact develops disconnection at Stn A.

3. Line is open/short circuit or offering high resistance.

4. PB1 button contact develops disconnection at Stn. B.

5. Local battery disconnection or weak at Stn. B. It shall be 24 V.

6. BLR relay not picking up at Stn. ‘B’ when PB1 pressed at Stn. A due to some fault.

7. Diode, in series with BLR/ NR punctured.

8. Relay contacts NR, BLR, PBPR offering high resistance at Stn. A & Stn. B.



9. When PB1 is pressed at Stn. A, BLR shall pick up at Stn. B. Suppose BLR is not picking up, check up the incoming line voltage at Stn. B across L1 & L2(Terminal No. 25 & 26 working voltage 24 Volt. If voltage is available and relay is not picking up, check for working current ( 110 mA.).



Sr.no.

Fault Condition


2. Failure of Lock Magnet.

Ensure the following:1. SM’s key ‘ON’ contact is making.2. Relay 1R front contact is making

(checking up the slides/ levers/ block signals ‘ON’).

3. TER cold contact in TER.4. Switch S1 & switch S2 in ‘N’.5. Back contact of relay 2R & relay 3R is

making.6. Relay TRSR front contact is making in

case of turning the block handle from ‘N’ to ‘L’ including check lock.

7. Relay TRSR back contact is making in case of turning the block handle from ‘N’ to ‘R’, ‘T’ to ‘N’, ‘L’ to ‘N’.

8. Block handle contact XX/, in case of turning block handle from ‘N’ to ‘L’.

9. Block handle contact BDY, in case of turning block handle from ‘N’ to ‘R’, ‘R’ to ‘N’, ‘L’ to ‘N’ respectively..

10. Front contact of relay NR is making.11. Front contact of relay CR2 is making

for turning the Block handle from ‘N’ to ‘L’.

12. Front contact of relay CR1 is making for turning the Block handle from ‘N’ to ‘R’, ‘R’ to ‘N’, ‘L’ to ‘N’.



13. Local battery voltage 24 Volts.14. Ensure cross protection contact viz.

CR1 & CR2 breaking during the respective operations.



Sr.no.

Fault Condition


3. Failure of relay 1R

1. Ensure voltage of location battery 24 Volt.

2. All block signals at ‘ON’ concerned levers/slides normal.

4. Failure of relay 2R

Ensurea. TAR pickup while train arrives. If

TAR is not pickup, check TAR circuit.b. TAR front contact making properly.c. Stick circuit is taken through block

handle contact LB/RD, check the block handle contacts.

4. Failure of relay 3R.

Check TER circuit, SM’s key contact, Switch S1, ‘R’ contact, TER hot contact, TEPR circuit, TER cold contact, Block handle LX contact.

5. Failure of PBPR relay.

Check the PB1 & PB2 contact of push button, 1R front contacts. When Block handle is in (RD) check up Block handle contact, TOLR front contact, check SM’s key contacts.

6. Failure of relay TRSR at train sending end ‘A’

1. Check for CR2 front contacts NR front contacts, 1 TPR front contacts.

2. Block handle contracts XX/, LX.3. Local voltage 24V(Including fuses

etc.)4. 3R back contacts.5. If stick feed is not available, check



TRSR front contacts, make before break contacts of XX//LX/.

6. Check the condenser across TRSR.



Sr.no.

Fault Condition


7. Failure of TOLR at ‘A’

A. Pickup circuit for TOLR.

i) Ensure TRSR show to release feature (condenser)-(slow to release)

ii) Ensure TRSR front contact making.iii) Ensure ITPR back contact making.iv) Ensure Block handle contacts LB

making.v) Ensure 3R back contacts making.

B. Ensure stick feed to TOLR.

i) Ensure S2 normal contacts making.ii) Ensure TOLR front contacts making.iii) NR back contacts making.iv) TRSR back contacts making.v) 3R back contacts making.

8. Failure of TOLR at Stn. ‘B’.

i) Ensure CR2 front contacts making.ii) Ensure NR back contact making.iii) Ensure block handle RD contact

making.iv) Ensure local voltage 24 Volt.

9. Failure of CR1/ CR2

Ensure at code receiving end.If CR1 & CR2 are picking up. Check at the receiver test terminals for (a) 24V DC input to receiver (b) FM input. If DC input is absent check the block handle contact



XY/LB/RD. If FM input is present checkup the level. If the level is OK, adjust the attenuator. If the level is low at the TX, check the level low/high/medium.

Sr.no.

Fault Condition


If the level is OK, check the frequency for CR1 carrier frequency 1800/2700 Hz./ Modulated frequency 85 Hz, for CR2 carrier frequency 1800/2700 Hz./ Modulated frequency 65 Hz. If the level and frequency OK check the FM input path in to RX. At the TX end check DC input, TX freq. Loop circuit for FM, which includes block handle contacts N, R & L.

10. Failure of Last Stop Signal circuit.

Check for ASR:- TRSR front contacts, S1 normal contact, LA contact of block handle, 1R back contacts.

11 Failure of Home Signal

Check for HSR circuit:- S1 normal contacts & RY/ LB contact or ( S2 reverse contacts & L of block handle for push back operation).

12 Premature TOL

Stick feed to TRSR cut off due to ITPR momentarily dropped due to unknown reason before train enters into section. Check the TPR circuit, if OK, check track circuit & block handle’s LX/ contact .



13 Normal cancellation not possible.

TRSR dropped due to momentary dropping of 1 TPR or 3R circuit. LX/

contact not making. Check S1 switch R contacts in TER circuit and 3R circuit are making properly. Check 1R front contact and SM’s key contact.


notes on diado block instrument

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