neals token instrument

SINGLE LINE BLOCK. 1

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TEACHING NOTES

ON

NEAL’S SINGLE LINE

BALL TOKEN BLOCK

INSTRUMENT

SIGNAL & TELECOMMUNICATION TRAINING CENTRE, BYCULLA, MUMBAI

( I S O 9001-2000 CERTIFIED )


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CONTENTS PAGE NO.

1. INTRODUCTION 03

2. VARIOUS PARTS OF NEALE’S INSTRUMENT AND THEIR USES. 06

3. POLARITY OF BALL TOKEN B/INSTRUMENTS 11

4. CIRCUITRY EXPLANATIONS 11

5. MODIFICATIONS IN R.E. AREA 13

6. TESTING OF BLOCK INSTRUMENTS 14

7. FAULT FINDING 16

8. BLOCK EARTH 17

9. TOKEN BALANCING 18

10.CIRCUMSTANCES WHERE B/INSTT. KEPT SUSPENDED 19

11.DO’S AND DON’TS, MAINTENANCE 20

12.MAINTENANCE SCHEDULE FOR NEALS B/INSTT. 21

13.TROUBLE SHOOTING 23


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LESSON: ONE

SINGLE LINE TOKEN BLOCK INSTRUMENT

A. INTRODUCTION:

Block instrument is used for controlling the trains in between two stations. The object of

providing block instruments is to prevent more than one train in the block section at a

time, and when the block section is clear it should be possible to admit one train in to the

section from either of the two ends, thus guaranteeing absolute Safety in the running of

trains at all time, maintaining space interval between two trains. To achieve this two

block instruments are inter connected electrically and provided one at each end of the

block section. Authority to proceed in to block section is a token in single line section.

Thus block instrument is called TOKEN BLOCK INSTRUMENT.

This instrument is designed to have conscious co-operation of the two Stationmasters at

either end of the block section for electrically releasing a Token from any one of them.

Mechanism & system are provided in such a way to ensure that only one token can be

released at a time from either of the instrument connected electrically. This block

instrument is used in single line section where number of trains is less.

B. ESSENTIAL OF ABSOLUTE BLOCK SYSTEM (GR 8.01):

(1). Where trains are worked on the Absolute Block System:

a) No train shall be allowed to leave a block station unless Line Clear has been

received from the block station in advance. And

b) On double lines such line clear shall not be given unless the line is clear, not only

up to the first stop signal at the block station at which such line clear is given, but

also for an adequate distance beyond it:

c) On single lines such line clear shall not be given unless the line is clear of trains

running in the same direction, not only up to the first stop signal at the block

station at which such line clear is given, but also for an adequate distance beyond

it, and is clear of trains running in the direction towards the block station to which

such line clear is given.

(2). Unless otherwise directed by approved special instructions, the adequate distance

referred to in clauses (b) & (c) of sub-rule (1) shall not be less than:

a) 400 meters in case of two-aspect lower quadrant signaling or two-aspect colour

light signaling, and

b) 180 meters in case of multiple-aspect signaling or modified lower quadrant

signaling.


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C. GENERAL REQUIREMENT OF BLOCK INSTRUMENTS:

1) CONSTRUCTION & TYPE: All block instruments must be robust type

construction and of a type approved by the Commissioner of safety.

2) LIGHTENING PROTECTOR: All instruments must be provided with an

efficient lightening protector.

3) PREVENTION OF IRREGULAR OPERATION: There must not be any

opening giving access to the interior of the instrument, through which it is

possible to operate the mechanism by any irregular means.

4) LOCKING & SEALING FACILITIES: Both locking & sealing facilities must

be provided on the instruments.

5) ISOLATION OF TELEPHONE CIRCUIT: Telephone or telegraph

instruments must be provided in conjunction with block instruments. It is

desirable that the condenser or other means provided for isolating the telephone

circuit from the instrument circuit is located within the instrument.

6) PREVENTION OF UNAUTHORISED OPERATION: A lock or other device

should preferably be provided to enable the station master to prevent unauthorized

manipulation of the instrument during his absence. SM’s key prevents the

unauthorized operation.

D. SPECIAL REQUIREMENTS (FEATURES) OF SINGLE LINE TOKEN

INSTRUMENTS:

GENERAL: This block Instrument is of robust construction and of a type approved by

the Commissioner of Railway Safety to with-stand rough handling by non technical staff,

not only at the Block Stations, but also at out laying siding controlled by the token of the

block Section.

a) OPERATION BEFORE GIVING LINE CLEAR: The instrument is so

designed that the SM has to go through definite moving operations on the

instrument in addition to the working of bell, key or plunger.

(1) Before he can give Line clear to the S.M. at the other end of the section to

release a token and

(2) Before he can obtain a token, even with the permission of the S.M. at the other

end of the section (SEM para 207).

b) FIXED INDICATIONS: The instrument receiving Line clear show a definite

fixed indication that a token has presumably been extracted and similarly the

instrument giving Line clear also shows a definite fixed indication that permission

has been given for the extraction of token. Such indications are locked

immediately a token is extracted and so remain until the token is replaced in one

of the instruments (SEM Para 208).

c) EXTRACTION OF TOKENS: Both Instruments must be restored to normal

before a further operation of extracting a token can be carried out. It should not be

possible to restore the instruments to normal without the co-operation of the S.M.

of the other end. (SEM Para 210).


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d) INTERLOCKING LAST STOP SIGNAL: Provision shall be made for

interlocking the L.S.S. with the “line clear Indication” of the block instruments.

(SEM Para 213)

e) CURRENT INDICATOR: An indicator, operated by incoming and outgoing

line currents must be provided (SEM Para 209).

f) OPERATION OF LINE CLEAR RECEIVING AND GIVING

MECHANISM: It must not be possible for the mechanism which permits a line

clear to be received and that which permits a line clear to be given to be in

operation at the same time. (SEM Para 211)

g) DESIGN OF INSTRUMENTS:

(a) The instruments must be so designed that a token of one block section can not

be placed in the instrument of an adjacent section.

(b) The token for each section must be engraved with code initials of the stations

at both ends of the block section and with a serial number (SEM Para 212).

TYPES OF NEALE’S TOKEN INSTRUMENTS:

(i) Block Instrument Single Line, Neale’s Ball Token, Type ‘A’(SA 20701) fig.1

(ii) Block Instrument, single Line, Neale’s Tablet Token, Type ‘B’(SA 21701)

(not used in C.Rly.).Fig. 15.


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LESSON: TWO

NEALE’S BALL TOKEN BLOCK INSTRUMENTS:

A. PARTS:

1. BELL UNIT: This is used to communicate the prescribed bell code to the Station

at the other end. The bell is of single stroke type. It works in the local circuit in

series with one of the two locks coils viz. ’TCF’ or ‘TGT’ through the contact of

the polarized relay, which operates with line current. Its coil resistance is 28

Ohms & minimum-working current is 80 mA.

2. POLARISED RELAY: This is a three-position relay, which works on the line

current. The movement of the contact spring depends on the polarity of the line

current. It has a resistance of 77 ohms and has a pick up value of 15 to 18mA and

rated current of 25mA.

3. NEEDLE INDICATOR (GALVO): This an electromagnet coil of 150 ohms

and requires a working current of 15 to 25 mA. A Needle is attached to the front

of an axle, which moves between two permanent magnets situated inside. The

needle is free to move either side depending on the direction of current. It is used

to detect the presence of incoming & out going current. An anti-clock wise

deflection of needle always indicates the operating handle is in one of the two

turned positions namely TCF or TGT. The clock wise deflection indicates that the

operating handle is in the vertical (line closed) position except when a token is

inserted in to the instrument with the operating handle in either TCF or TGT

positions & plunger is pressed.

4. FORCE DROP ARRANGEMENT: It is a mechanical arrangements adopted to

ensure that the lock controlled by an electro magnet becomes effective (i.e.

equipments get locked) after the de-energisation of the lock coil.

NEED: any lock control/operated by an electro magnet gets released whenever

the lock coil is energized and the lock becomes effective (equipments get locked)

once the lock coil is de-energized.

But if due to residual magnetism or mechanical friction, the armature of the

electro magnet remains stuck up in energized position even after the supply to the

coil is cut off, the lock will become permanently free and will not effective for

future operation, which is unsafe. So to prevent this unsafe condition, force drop

arrangement is provided.

In Neale’s Block Instruments, force drop arrangement for TCF/TGT lock is very

important from safety point of view. It is achieved through the bent lever and

projection made on lock replacer disc.

TCF&TGT LOCKS WITH FORCED DROP ARRAGNEMENT: These two

locks are identical and their coils are wound to a total resistance of 28 ohms and

require an operating current of 160 mA at a minimum working voltage of 4.5V.

The units with the armature and rocker arm in position are not interchangeable

between the two. The rocker arm is fixed to the base of the lock coil assembly,

the armature, which is free to move, carries a lock on a spindle at one end. The


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pawl (TCF/TGT) normally rests on the cam projection of the lock replacer disc,

thus mechanically ensuring the locking of the operating handle through the

locking of rack.

The pawl (TGT/TCF) drops only when the operating handle is pulled out of the

slot. When the lock coil is energized and the operating handle is pulled out, the

armature is attracted fully and lifts the locks from the locking notch in the rack.

This permits the operating handle to be turned either to ‘TGT’ or ‘TCF’ position

depending on whether TGT coil or TCF coil is energized. The TCF coil energizes

for three operations i.e.

I) For turning the operating handle from line Closed to TCF.

II) For turning the operating handle from TCF to Line closed.

III) For turning the operating handle from TGT to Line closed.

The TGT coil energizes only once for turning the operating handle from Line

closed to TGT position. The lock replacer disc has four projections A/B/C/D on

its periphery (Fig.2). The three projections A/B//C are of the same size all these

projections ensure forced dropping of the locks.

The fourth projection ‘D’ is deeper than the other three projections and forces

the TGT lock pawl down even when the operating handle is in pulled position.

When the operating handle is turned about one third from Line closed position

towards TGT, the projection engages with the lever of the TGT lock. This

coincides with the momentary interruption of the line current by inter-stoke

interrupter (jerking contacts) with the momentary interruption current. TGT coil

is de-energized and the TGT lock pawl is forced down by this projection on the

rack and thus lock pawl engages in the check lock position. Lock pawl is again

released only when the line circuit is completed by the jerking contacts when

the operating handle is turned a little further and the other station is continuing

to keep the tappet rod pressed thus prolonging the last beat.

5.INTER STROKE INTERRUPTOR (JERKING CONTACTS): Two contact

pieces with a gap between the two are provided on a bakelite mounting on the

spring clutch shaft. In the line closed position of the operating handle, the line

circuit is made through by two springs resting on the bottom contact piece. When

the operating handle is turned, the clutch shaft is also rotated by a rod connected

to the pinion on the operating handle. Due to operation of the operating /bottom

handle, the contact spring moves over from the bottom contact piece to the top

piece causing a momentary break in the line circuit. This will cause a deflection

in the needle indicators. The deflection indicates to the S..M. at the current

sending end that the operating handle is being turned at the other station.

6. CONTACT ARRANGEMENT: This consists of four finger springs mounted on a

insulated lever below the commutator. The lever moves in an arc through a

connecting rod which moves whenever the plunger is pressed. This will result in

the spring making contact with the segments mounted on the commutator.

As seen from the back of the instrument, battery terminals are connected to the

first and third finger springs and earth to the second spring and line through

Galvanometer to the fourth spring, the commutator in line closed position of

operating handle puts through springs 1.2 & 3,4 when the plunger is pressed.


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When the operating handle is turned to TCF or TGT, Springs 1,4&2,3 are put

thorough by commutators thus reversing polarity of applied voltage.(fig.3).

7. SAFETY CATCH (Fig.4): This is a small steel piece in a hook form resting on a

small projection on the spring clutch shaft. This catch plays a very important role

in preventing the declutching of the commutator shaft when the operating handle

is being turned from Line closed position to TGT or TCF position and in the

turned position of the handle the projection moves away from the safety catch and

this permits the de-clutching of the commuator shaft when the token is inserted

and the plunger is pressed.

If the safety catch is not provided or if it is not functioning properly and if the

cummutator shaft is not free due to jamming or for any other reason then the

spring clutch shaft would declutch and turn over with the operating handle, when

the operating handle is being turned from Line closed to TCF position, for

granting permission to approach, there by leaving to commutator normal. As

there is no change in commutator the operator at the dispatching end can turn his

handle to TCF position only and cannot go to TGT position. This results in block

failure. If, however, the commutator shaft sticks in the instrument receiving

“Line clear” then the handle would have been turned to “TGT” thereby obtaining

a token but having the commutator in normal position. It would create an unsafe

condition as under.

After departure of the train, the train receiving station can turn the handle to “Line

Closed” since the commutator is normal at the train sending station. Also at the

train sending station, the operating Handle can be turned to “Line closed” with the

co-operation of the train receiving station. Under these conditions both the

instruments would be in line closed position with a train in the Block Section.

Hence maintenance staff/Inspectors should take special care regarding the

proper functioning of the Safety catch.

8 S.M’s LOCK: S.M. lock is a mechanical locking provided on a block

instrument, to prevent an unauthorized operation of the block instrument in the

absence of the Station Master. SM’s key when out will mechanically lock the

operating/ bottom handle and Top Handle, thus preventing them from

manipulation. Operating/Bottom handle can be locked in any of the three

positions. SM lock up key when out will also disconnect the line battery and thus

unauthorized bell codes cannot be sent to the other station. However incoming

bell codes are not affected.

9. TOKEN RACES OF A BALL TOKEN INSTRUMENT: There are four races

and a token dropped into the instrument, can get into any of the four races at

random. Thus, it is not possible to know in advance the serial number of the token

that will come out next.

10 TOKEN INDICATOR (Fig.5) : This is a mechanical indicator gives an indication

to the operating staff whether any token is present in the bottom handle or not. It

works on the principle of gravity drop. An “S: shaped swinging lever is pivoted on

the token selector plate. The top end carries a flag indicator painted red & green and

mounted in a such a manner as to be seen through a glass opening in the front of the


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instrument. Its bottom is rounded off & presses against a token in the token drum

& displays a green indication. If there is no token, the lever revolves under its

own weight & the rounded end enters in to the empty space in the token delivery

drum locking the same and prevents the bottom handle being turned to TGT when

there is no token in the Instrument and changing the indication to red. This

however does not prevent bottom handle from being turned to TCF position.

11. SUPER IMPOSED TELEPHONE: A telephone is superimposed on the line

wire by means of an induction coil and a condenser. The condenser isolates the

telephone circuit from the Block Instrument Circuit. The Telephone is lying on

the bracket which disconnects the Telephone circuit from other circuit.

12. TOP HANDLE (TOKEN RECEIVING DRUM): It is a cylindrical cast iron

drum with recess to take one token. The recess opens at the top through an

aperture in the drum housing normally covered by a hinged metal cap. In this

position the arrow marked on turning handle faces vertically upwards. A token is

inserted into the instrument by placing it in this recess by lifting the hinged cap

and then turning the handle anticlockwise (by handle provided on the front)

through approximately 190 degree. The recess is provided with a small fixture

called the “Spigot”. The shape of the Spigot corresponds to the hole

configuration on the token used in the block section. The purpose of this Spigot is

to prevent insertion of a wrong class of token to clear the section. Two spring

operated lock pawls are located one each at approximately 85 & 170 degrees with

in the drum housing. These lock pawls normally press against the surface of the

drum and do not therefore, interfere with its movement if it is turned with a token

of correct dimension in its recess. Should the drum be turned in the anti clock

wise direction with its recess partially or completely empty, the first lock pawl at

85 degree from the vertical position gets into the token recess and checks its

further rotation. Should the first lock pawl fails to detect the correct token in the

recess, the second lock pawl will check rotation beyond 170 degree. The token so

consigned is led through chute (which has no bottom) whose sides are carved

sufficiently inwards to guide the token. The token enters the recess directly in the

line closed position of the Bottom Handle, But in the other positions of the

handle it rests on the token receiving jaw. The chute ensures that foreign objects

(such as , bolts or nuts) inserted into the token receiver will not run down into

recess but will fall right through to the bottom of the instrument. The top handle

is provided with a lock, to lock it in the turned position between 75 to 85 degree,

by removing the SM’s key. This arrangements prevents the insertion of the token

in the absence of the Station Master on duty.

13.BOTTOM HANDLE – OPERATING HANDLE – BLOCK HANDLE WITH

TOKEN DELIVERY DRUM: The bottom handle is situated at the front middle

bottom of the Instrument. The tappet rod is threaded through the centre of the

handle. The handle has three positions which gives the condition of the block

Section as indicated below (Fig. No.6).

(a)The handle with its arrow pointing vertically upwards indicates Line Closed.

This is normal position.

(b)The handle with its arrow points to the right, indicates that Line clear for a

train, has been given. This is called the “Train coming from (TCF) position.


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(c)The handle with its arrow pointed to the left, indicates that Line clear has

been obtained and a token extracted. This position is called ”Train Going

To”(TGT).

The token delivery drum forms an extension of the operating handle and is a

heavy cast iron cylinder with a suitable recess in it to house one token. From this,

the token is delivered when it comes out of the opening in the front when handle

is turned to the TGT position. A toothed section (Pinion) is mounted on

hexagonal extension at the end of the drum which works a rack below it every

time the block handle is turned. A rod connecting this sector to the spring clutch

shaft and the token selector causes both these to rotate along with the handle. The

movement of the rack, when the handle is turned is prevented normally by two

locking pawls engaging with notches cut in the rack as shown (fig.2). The

movement of the handle from any particular position (Line Closed, TCF or TGT)

is possible only when the proper locking pawl has been released from the notch in

the rack which can happen only through the co-operation of the distant station.

14. TOKEN POUCHED AND HOOPS: The token extracted from block instrument,

to hand over it to the driver to enter into the block section with his train, is

protected by token pouch. The pouch is attached to the Line clear hoop/stick.

This prevents the token from damage while handing over or receiving the token

by a driver of a through running train. The pouch/hoops/Line clear stick are

periodically checked and damaged pouches/hoops/Line clear sticks are not

allowed to be used.

15.LAST STOP SIGNAL CONTROL:

a) MECHANICAL : A separate ‘E’ type lock is attached on the TGT side of the

instrument to have a mechanical control over L.S.S. A small extension piece is

screwed on to the rack on the TGT side. In the normal and TCF positions of the

operating handle, the plunger of this lock will get obstructed by the extension

piece of the rack due to which the key of the same can not be taken out . In the

TGT position of the operating handle only the rack comes out of the lock

enabling it to be locked by taking out the key. This key is utilized to take off the

LSS either by inserting it in the mechanical lock on the LSS lever or utilizing it to

release the SM’s control Instrument. Once this key is taken out of the lock, the

lock plunger will foul the rack and the operating handle cannot be turned from the

TGT position unless and until the L.S.S. control key is brought back, put back

into the lock and turned. (The details are given in figure 11).

b) ELECTRICAL: A metallic extension piece attached to the lock replacer disc

which is called TGT stud, bridges two contact springs when the block handle is

tuned to TGT position. The L.S.S. Reverser feed is taken through this contact,

ensuring that the L..S.S. can be taken off only when the block handle is turned to

TGT position.

On single line sections where Token block Instruments are provided, the

following controls must on the L.S.S.

(I) One slot, one train.

(II) Provision for automatic replacement of L.S.S. with the passage of train.


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16. CLASS OF BALL TOKENS: The tokens used in Neales Ball token Instruments

are hollow round steel balls. They have a through groove cut on a diametric axis

which have one of the following configuration.

(A)Round hole. (B)Rectangular hole. (C)Triangular hole

(D)Four sides hole. (E)Five sides hole.

Different hole configurations are provided to distinguish the tokens belonging to

block Instruments of different block sections. It ensure that a token belonging to

instrument of one block section can not be inserted into an instrument belonging to an

adjacent block section thus preventing wrong normalization of Block.

The different hole configurations viz. Classes A,B,C,D,&E are as shown in the figure(7)

B. Polarity In a pair of instruments used for a block section, one instrument is wired for normal

polarity and the other for reverse polarity(Fig.8)

In normal polarity instrument, the positive of the Battery is connected to the line, when

the tappet rod is pressed in the “Line Closed” position of the bottom operating handle.

Further a positive polarity on the line is required to turn the operating handle to TGT

position.

In reverse polarity instrument, the Negative of the battery is connected to line when the

tappet rod is pressed in the “Line Closed” position. A negative polarity on the line is

required to turn the operating handle to TGT position.

The reasons for providing a pair of different polarity instruments is to prevent the

possibility of obtaining two tokens simultaneously one at each end of the section in the

event of the block line coming in contact with another conductor of favorable polarity.

A normal polarity block instrument can be converted into reverse polarity or vice-versa if

necessary by reversing the connections of (1) Galvo (2) polarized relay and (3) line

battery and altering the terminal designations.

The Block Instrument has a capacity of 36 tokens. Normally 32 or less tokens only are

used in a pair of instruments.

C. CIRCUITRY EXPLANATION:

Working of the block instruments: (To dispatch a train from station A to station B)

‘A’&’B’ are two adjoining Stations (fig 8) provided with normal and reverse polarity

Instruments respectively connected by overhead line wire with earth or Metallic return.

SM at ‘A’ has to dispatch a train to ‘B’. ‘A’ asks ’B’ for “Line clear” on telephone and

then by sending the authorized bell code signals and prolongs the last beat. The

prolonged beat energizes the TCF lock coil at ‘B’ and lock pawl clears the rack for

moving the block handle from line closed to TCF position. On seeing the needle

deflection A releases the plunger.

The Ckt. is shown in fig.9

Needle indicator at ‘A’ & ‘B’ deflects to the right . The tongue of the polarized Relay at

‘B’ deflects to ‘R’ completing a local series circuit of block bell and TCF lock coil. When


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the handle is being turned at ‘B’, there will be a jerk in the indicator needle, both at ‘A’

and ‘B’ due to jerking contacts momentarily breaking and again making. The block

handle having been turned at station ‘B’ to TCF position the commutator is reversed at

that station.

Plunger at ‘B’ is pressed will now send a +ve current on line. ‘B’ now sends authorized

bell code signals to ‘A’ and prolongs the last beat. ‘A’ having a steady deflection of the

top of the needle to the left turns his block handle from Line closed’ to ‘TGT” position

and obtains a token.

The Ckt is shown in fig.10.

The tongue of the polarized relay at ‘A’ is attracted towards ‘N’ completing local circuit

for the block bell and TGT lock coil in series. There is one bell beat at ’A’ and the TGT

coil being energized and armature is attracted. TGT lock pawl is lifted when block

handle at “A” is pulled for operation, and the handle is free to be turned to TGT position

While the block handle is being turned to TGT position, if the train receiving station

releases the plunger, the block handle at the dispatching station gets locked in the check

lock position and can not be fully turned to TGT position. So continuous co-operation by

pressing plunger is given by the train receiving station to turn when the handle to full

TGT position at ‘A’ and a Token is delivered.

In this condition of the block handle, either the LSS control key can be extracted (fig.11)

or the LSS electrical control contact is made. In the case of mechanical control, the key

extracted from the block Instrument is used either in the SM’s control apparatus or in the

signal lever controlling the LSS. Once the train clears the LSS, the signal is put back to

ON position. Train entering section code is sent to the stations in advance. The LSS

control key is inserted into the block instrument at ’A’.

Driver on arrival at ’B” hands over the token to SM. S.M. at B calls attention of SM at

‘A’ and on being acknowledged inserts the token into his Instrument. And gives bell

signals for ‘train out of Section’. This changes his commutator to Normal “B” prolongs

the last beat and SM at ‘A’ observing the indicator needle deflection turns the handle

from TGT to ‘Line closed’ position. This changes his commutator also to normal.

The Ckt. shown in fig. 12 .

‘A’ now acknowledges the “train out of Section” signal prolonging the last beat,

Commutator at ‘A’ having been changed to normal, the prolonged beat energizes the TCF

coil at ‘B’ enabling him to turn his block handle from TCF to ‘Line closed’ position

both instruments are now in ‘Line closed position.”

CANCELLING OF LINE CLEAR: After obtaining line clear and extracting a

token, if SM at ‘A” does not dispatch a train for any reason, he can cancel the “Line

clear”. ‘A’ informs ‘B” about his intention of not dispatching the train and inserts the

token into his Instrument. ‘A’ sends bell signals to ‘B’ for cancelling line clear,

prolonging the last beat. The insertion of token and plunging changes his commutator.

The polarized relay at ‘B’ is energized to release the TCF lock which enables him to

turn his block handle to line closed from TCF position. The station B acknowledges the

cancelling signal prolonging the last beat. This enables A to turn the block handle from

TGT to Line Closed position.

NOTE : Station having token should turn the block handle to normal at last.


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D. Modification in RE area:

Additional requirements in 25 KV 50 Hz electrified areas :-

Any circuit in the vicinity of 25 KV AC electrified section is likely to be influenced by

electrostatic and electromagnetic induction. These induced voltages may cause

undesirable and unsafe conditions on signal and Telecommunication equipment. So

protective measures are adopted to minimize unsafe condition due to induced voltage.

When these instruments are to be used in 25 KV AC electrified areas, a filter circuit in

conjunction with a Train wire and Block Bell Equipment is used and the circuit is

modified as shown in fig. 13. X & Y relays are introduced to prevent the operation of

the polarized relay by the condenser of the filter unit discharging through it after

plunger is released. X being slow to release puts through the shunt resistance of 5,000

ohms across the condenser when plunger is released thereby discharging the condenser

through the resistance and protecting the polarized relay.

FSS PROVING CIRCUIT:

As per GR 8.03(2-B) at a class B station on single line , the line shall not be considered

cleared and line clear shall not be given unless.

All necessary signals had been put back to ON behind the said train.

To fulfill this requirements a GPR relay (receiving signal normal proving relay is used.

Front contact of this relay is proved in the energisation circuit of TCF coil.

GPR in energized condition proves that first stoop signal is at ON position.(as shown in

fig. No. 8).


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LESSON: THREE

TESTING OF INSTRUMENTS:

Test to be conducted after installation and before commissioning the instrument. Check

that the correct polarities are connected to the instrument at both ends. This can be

checked as follows.

(a) With the commutator in normal position when the plunger is pressed, the feed

on the line must be positive and earth negative for a N P instrument. To

check this connect the volt meter positive lead on line terminal and negative

to the earth terminal. The volt meter should give a forward deflection for the

correct connection when plunger is pressed. Similarly for R.P .instrument

check that the feed on Line is negative and earth +ve.

(b) With incoming positive polarity on line, in a N P Instrument polarized relay

should deflect towards left/(TGT side) & with (-)ve incoming polarity on line

a R. P Instrument the polarized Relay should deflect towards left (TGT side).

(c) Where earth return is used, check the earth resistance If it is more than 10

ohms suitable measures should be taken to reduce this.

(d) Check that all mechanical parts are free to move without undue friction and

that there is no jamming of moving parts.

(e) Connect the two block Instrument in the block section. Do not energize any

of the lock coils, try to forcibly turn the operating handle to “Train going to”

and “Train coming from “ positions. It shall not be possible to turn the

handle, of either of the instrument either to TGT or TCF positions. This

ensures that the TGT & TCF locks are properly functioning.

(f) Energize momentarily the TGT lock coil of either instrument as in the normal

operation. Turn the operating handle slowly towards TGT, when the lock

pawls is out of notch in the rack, de-energize the lock coil and turn the handle.

Ensure that the lock and pawl engages the check lock notch in the rack, and

the handle can not be turned further, till the lock coil is re-energized.

(g) Energize momentarily the TCF lock coil of either of the instruments. Turn the

block handle to TCF. There is no check lock in the TCF side.

(h) With the bottom/operating handle in TGT position and without energizing the

TCF lock, try to force the block/operating /bottom handle to line closed

position. It shall not be possible to do so unless the coil is energized. Repeat

the test with the handle in the TCF position.

(i) Extract tokens in the normal sequence of operation and restore the instrument

to the line closed position.

(j) Extract a token and replace it in the same Instrument as is done in the case of

canceling “Line clear” and see that the commutator changes when the token is

plunged in. Repeat the above operations ten to twelve times.


.

(k) Check the commutator does not changes unless the token gets into the races in

the case of ball token instrument and slides down the rail beyond the tablet

receiver in the case of tablet token instrument. Also ensure that the token does

not enter the recess or slides down the beyond the tablet receiver unless the

commutator changes. Repeat this ten to twelve times.

(l) Check that operating handle remain locked when the instruments are out of

phase i.e. when the token is out of any of the block instrument.

(m) With operating handle in the line closed positions when the bell plunger of the

Normal polarity instruments is pressed, check that the needle indicator at

both the stations deflects towards the right. If it does not, battery terminals

are not properly connected.

(n) Put all the 36 tokens in either block instrument and ensure that there is no

jamming of token.

(o) Remove all tokens from the instrument and ensure that the token indicator

functions properly and prevents the block handle from being turned to “Train

going to” position from “Line closed” position. It shall not prevent the handle

from going to “Train coming from” position.

(p) Turn the handle to ”TGT” positions slowly and see that the Token is not

released from the instrument before reaching the “TGT ”position.

(q) Check that even after the handle is turned to “TGT” position the token is not

delivered until the block handle is locked in the notches on the body. This test

is required to ensure that “TGT” lock is forced dropped before the delivery of

a token from the Instrument. Otherwise it would be possible to return the

handle to normal and come to “TGT” again with a second token in case of

TCF lock sticking up of lock armature due to residual magnetism or

Mechanical faults.

(r) Extract a token in the sequence of operation and check the cancellation of

“Line Clear” for its’ proper functioning.

(s) Check and ensure the full deflection of the needle indicator.

(t) Check that the safety catch is functioning properly and prevents the

declutching of the spring clutch shaft from the commutator shaft whenever the

operating Handle is turned from “Line Closed” to “TCF” or “TGT” position.


.

FAULT FINDING:

CREATE THE FOLLOWING FAULTS & CHECK RESULTS:

(a) Both the instrument in ”Line closed” position.

________________________________________________________________________

Nature of faults Whether token can be Whether token can

Obtained at to be obtained at

(Normal Polarity) (Reverse Polarity)

Station ‘A’ Station ‘B’

________________________________________________________________________ (i) Positive of foreign source

on line & negative on earth YES NO

(ii) Negative of foreign source

on line & positive earth NO YES

(b) With instrument ‘A’ in ”TGT” and at ‘B’ in “TCF” position.

(i) Positive of Foreign source NO NO ‘B’ can turn his

on line & negative on earth handle to line Closed

_______________________________________________________________________

(ii) Negative of foreign source No NO. A can turn his handle to

on line & positive on earth. line closed


.

LESSON: FOUR

BLOCK EARTH

Instructions in various manuals (Maintenance / construction)

(a) All Block earth and their connection must be examined at intervals of not less

than one month.

(b) All block earths must be tested for resistance at intervals of not more than 12

months and where the resistance exceeds 10 ohms action should be taken to

reduce the resistance. Where it is not possible to reduce the resistance of

earth within the maximum value, additional earths may be provided in parallel

(Para 944) all earths installed for protection circuits should be simultaneously

tested at least once a year.

Metallic Return wire is to be provided in electric traction area.

Metallic and earth returns:

(a) Earth wire should be as short as possible. It should be of a cross-section not

less than the size of the line wire and should not be smaller than 4mm dia. It

should be adequately secured or supported and must not have any spiral or

bend.

(b) Earth wire should be adequately protected from mechanical injury and be

efficiently connected to Earth.

(c) All connections to an earth must be well-soldered.

(d) It is desirable to have a metallic return to take care of multiple failure as

recommended in block manual.

(e) The block wire should be placed on top of the alignment so as to preclude the

possibility of foreign feed injunction in to the block line.

(f) Lightening discharger of striking voltage greater than normal working voltage

may be provided at both ends of the block line.

Measuring of block earth resistance, out going and incoming current:

1) Block earth must be tested within 12 months.

2) Earth resistance shall not be more than 10 ohms.

3) Method of finding out Resistance of Earth.

a) earth should be measured by means of whetstone bridge or G.P. O. detector or

megger or earth tester. Two iron bars with terminals fixed on them and suitable

length of wire should be used as temporary earths.

b)to test an earth two iron bars should be driven about 6 meters apart from the

earth to be tested. The bars should be used as temporary earth and driven in the


.

ground for 1 meter at a time then worked backwards and forwards so as to leave

as pace forwarding 0.2 meter. Salt water should be used to ensure that the bars

make a good connection with the earth. If salt water not available a weak

solution of Salammoniac in water may be used.

E1 Earth under test. E2 Temporary earth.

E3 Temporary earth R1 Resistance between E1& E2

R2 Resistance between E1& E3 R3 Resistance between E2 & E3.

Resistance E1 = R1+R2-R3

2

Measuring of outgoing and incoming current:

For measuring outgoing & Incoming current disconnect line wire from line terminal and

connect amp. Meter between line wire and line terminal.. Press the bell plunger of the

same instrument. Ensure that the outgoing current does not exceed the rated current of

polarized relay. This is meant to ensure that in no circumstances the polarized relay is

over energized.

Token Balancing:

(a) Maintainer must , whenever necessary transfer tokens from the instrument in

which these have accumulated to the Instrument at the other end of the Section.

Each Maintainer in charge of single line token Instrument must be provided with

a “Token Balance Book” consisting of Form No.1 S&T / TB annexure ‘G”

serially numbered. Each book before issuing must be endorsed by the issuing

inspector as under :

“Pages ______________________________to ______________ checked and

found correct”

b) Maintainers should extract an even No. of Tokens for transferring.

c) Maintainers must fill up portion ‘A’ & ‘B’ of token Balance Book form and

take the signature of

i) SM of the Station from where tokens have been extracted to verify that the

token number as mentioned were extracted from the instrument with his

permission.

ii) The receiving SM to verify that token numbers mentioned in the book have

been correctly deposited in the relevant instrument.

d) SM must have instructions to advise the Maintainer by Wire/Control message

as soon as the balance of Tokens in their token balance register falls to ‘Six”

except where token balances are in use (Para 741).

e) tokens which are deformed or have worn out under size or cracked or

damaged in any other way should be removed. Advice of removed tokens should

be given to all concerned by wire.

f) A lost token should be replaced with a Token of the next higher number in

continuation of the series in use on the Section in accordance with instructions


.

Balancing of Tokens: Signal Maintainers (Electrical) must comply with instructions regarding balancing of

tokens laid down in Para 741 Entries in the Token Balance Book must be made legibly

In ink”.(Para-1408).

The Neale’s Token Instrument shall be considered as having failed and working of

the Block Instrument shall be suspended in the following circumstances:

1) When bell signals are received indistinctly or fail altogether.

2) If the needle of the galvanoscope fails to move, when bell signals are given or

received or shows a wrong indication viz. to the right instead of left and vice-

versa.

3) When a token is broken or damaged in any way during or after extraction.

4) If a token can not be taken out from the instrument after proper signals have been

exchanged and no token is out from either instrument of a section.

5) When a token can be taken out from the instrument without proper signals being

exchanged with the station at the other end of the section.

NOTE : This test shall be made when the operators take change of the block instrument.

6) If a Token can not be put back into instrument or jams when being put back into

the instrument.

7) If a train arrives at a station without a token referring to the block section over

which the train has passed.

8) When the Token belonging to a block section has been over carried to another

station or is lost and can not be found.

9) When there is no token in the Instrument at the station from which a trains ready

to start.

10) When there is reason to believe that there is contact between the block wire and

any other circuit (Permanent or intermittent deflection in Galvo or irregular bell

beats heard without pressing the plunger on either end.)

11) If the operating handle can not be turned to any one of the three positions with a

prolonged beat from the distant station.

12) If the operating handle can be turned to any one of the three positions without

prolonged beat from the station at the other end.

13) If the dial glass of galvanoscope is broken.

14) If the instrument or is battery counter is found unlocked.

15) When the key of the token receiver drum is lost or the lock is out of order.

16) When the key of the clamp locked on the token handed over to the proceedings

train, is returned to the station in rear by the officer in charge of the motor trolley

following that train.

17) When a private number can not be obtained from the Station Master at the other

end of the Section through the Block telephone.

18) If it is known that the Instrument is defective in any way not specified above.


.

LESSON: FIVE

DO’s and Don’ts:

a) Do not bend the contact spring specially the finger contacts, unless

absolutely necessary to obtain contact pressure.

b) Do not bend the TGT and TCF Pawl unless absolutely necessary to adjust

the force dropping action.

c) Do not allow the Block Instrument to be in the circuit, if the safety catch on

commutator shaft is either broken or not functioning properly.

d) Do not file the rack notch or lock pawls, if they are not properly engaging,

remove them and re-adjust.

e) Do not open the polarized relay; if the seal is broken for any reason, it must

be removed from the circuit.

f) Do not make the SM’s lock up contact through under any circumstances.

g) Check the tablet releaser actuating link screw is intact. If these screws are

not in the position the tablet token can be released before operating the

handle is locked in the TGT position.

LOCKING AND SEALING ARRANGMENTS:

A sealing screw is provided in the back of the instruments which can be used for sealing.

In addition to this sealing facilities locking arrangements also is provided to lock the

instrument by maintainer (SM’s lock and Maintainer’s lock

MAINTENANCE OF TOKEN INSTRUMENTS:

1. Check that ball tokens are correct size otherwise it will get jam in the races of block

Instrument.

2. The Needle Indicator ( Galvo ) must be maintained properly so that they operate and

return to normal position correctly when released. The direction of the needle must

correspond to the polarity of the current flowing through.

3. Care must be taken to see that the token indicator on the ball token instrument is free

to move . The pin must be oiled once in a fortnight with axial iron medium grade IS 1628

for the movement of the indicator.

4. Check the forced dropping arrangement of TCF & TGT lock. Care must be taken to

check that the rocker arm is free about its fulcrum pins. The edge of the lock must be

squire if not the lock must be immediately changed to avoid any possible jumping off

from the notch in the rack. Similar care must be taken to see that the lock not be forced


.

out of the notch in the check lock position and thus allowing the operating handle to be

turned to TGT position.

5. See that the polarized relay armature is free and it returns to its normal position i.e.

neutral position, when the current is not flowing. If it does not return to its normal

position it indicates that either there is some residual magnetism or there is fiction in the

bearing. Replace the polarized relay immediately.

6. All batteries must be kept clean, terminals must be free from dust and corrosion.

Battery must be kept sealed check and ensure that lightening and power protective

devices earth and earth connections are effective and good condition. Care must be taken

to see that the correct polarity is maintained at the time of battery renewal.

7. Block Instrument telephone, telephone flexible cord and condenser or other means

provided for isolating the telephone from Block instrument circuit must be in good

condition for safe working of the instrument.

8. During routine maintenance, care must be taken to see that the safety catch provided

near the spring clutch type is in position and is free to move about its fulcrum pins

without any friction.

9. (a) Check that locking pawls are correctly safe squire end.

(b) Check that the notch in the rack are correctly safe and are squire where necessary.

© Check that spigot riveting is not loosed.

(d) Check that maintainer’s key and SM’s key can not be extracted in unlock

condition.

(e) Check that if screws bolts and nuts are loosed tightened them.

MAINTENANCE SCHEDULE FOR NEALE’S ‘A’ TYPE

TOKEN BLOCK INSTRUMENT:

Sr.No. Maintenance work to be done. PERIODICITY

E S M S I C S I

1. CHECK LOCKING AND SEALING F M Q

2. CHECK THE SM’S LOCKUP KEY F M Q

WORKING

3. CHECK THE OVERHAULED DATE. - HY Y

4. CHECK THE DISTINCTIVENESS - HY Y

OF THE TONE OF THE BELL.

5. CHECK THE LEVEL OF INSTRUMENT. M HY Y

6. CHECK THE POLARITY OF THE - Q HY

INSTRUMENT


.

7. CHECK AND ENSURE THE FULL F M Q

DEFLECTIONS OF THE NEEDLE

INDICATORS

8. CHECK THE TOKEN FOR DAMAGE F M Q

9. CHECK THE TOKEN INDICATOR F M Q

IS WORKING FREELY.

10. CHECK THE FORCED DROP F M Q

ARRANGEMENT OF TCF & TGT

AND THE EDGE OF LOCK

11. CHECK THE POLARISED F M Q

RELAY FUNCTION

12. CHECK THE FUNCTIONING OF F M Q

SAFETY CATCH.

13. CHECK THE SPIGOT FOR F M Q

ITS TIGHTNESS

14. CHECK THE TOKEN RECEIVER FOR -- -- Q

CORRECT TOKEN CONFIGURATION

15. CLEAN THE RACK AND PINION F M Q

TEETH & LUBRICATE WITH

AXLE OIL MEDIUM GRADE 1628.

17. INSPECT CONTACT SURFACES F M Q

18. CHECK EARTH CONNECTIONS F M Q

19. CHECK THE TELPHONE AND F M Q

TELEPHONE CORDS

20. CHECK THE BLOCK AND F M Q

TELEPHONE BATTERIES FOR

CLEANLINESS & RECORD VOLTAGE

RECORD

21. CHECK ALL WIRINGS OF THE -- M Q

INSTRUMENTS.

22. MEASURE THE LINE CURRENT F M Q

*F - FORTHNIGHTLY. *M – MONTHLY. *Q -QUARTERLY

Periodicity of Overhauling: Single line Token (Ball & tablet) Instruments

are required to be overhauled once in 10 years.


.

LESSON: SIX

TROUBLE SHOOTING:

TROUBLE REASON REMEDY

1. No deflection in

GALVO when bell

plunger is pressed at

sending station.

. AT SENDING STATION.

1. Line battery weak or any

cell in group has become

reverse polarity.

2. Finger Spring contact

broken, jerking contact not

making

3. Wire disconnection

4. Galvo coil open /Galvo

defective

5. Earth wire broken , line fuse

may be blown up

AT RECEIVING STATION

1. Rest contact not making.

2. Jerking contact open

3. High resistance on line

4. BPR relay coil open.

1. Check battery voltage

and current.

2. Check the spring contact

assembly.

3. check wire connection.

4. Check Galvo coil

5. Check earth resistance

1 & 2. . Check rest &

jerking contact pressure .

3. Clean the jumper wire

and tight the connection.

4. Check working current

of BPR and coil resistance

2. Galvo deflects but

bell beat is not received

at receiving station.

1. Local battery may weak.

2. TCF/TGT coil open.

3. Bell coil may defective

4. Bell armature may jam.

1. Check local battery

voltage and current.

2. Check the TCF/TGT coil

resistance, voltage and

current

3. Check bell coil

resistance & bell assembly.

3. Bell beat is received

but block handle is not

turned to TCF/TGT

position.

1. SM’s key may be out

2. Block handle jammed due to

jamming token in the races

1. Check SM’s key. It

should be In.

2. Check the block and

token thoroughly

4. Bell beats is received

without pressing the bell

plunger at sending /

receiving station.

Line contact fault. Check the line by foot and

rectify it.

5. when Bell plunger

pressed galvo deflects

Earth contact fault in section. Check the block line from

sending to receiving station


.

but no response at

either of station.

and rectify it.

6.SM’s key not

extracted, when

required by SM.

1. SM lock may be defective

2. Token receiving drum is not

turned fully.

1.Check SM’s .lock position.

2. Check the movement of

receiving drum.

7. Token is not

going into block

instrument.

1. Token hole shape has

damaged.

2. Token jammed with spigot

in token receiving drum.

1. Check the shape of token

hole if damaged remove it.

2. See that token should be

free in token receiving drum

8. Token is inserted

but block is not

getting normalized.

1. Commutator shaft has not

been changed after insertion of

token and pressing the bell

plunger.

1. Check the spiral spring

condition between commutator

shaft and spring clutch shaft.

2. Check that commutator

shaft is not jammed.

9. Block handle is

not going from line

closed to TCF.

1. GNR relay may drop.

2. Normal band of circuit

controller of outer signal may

not make.

3. NTR may drop.

1.Check the power supply,

fuse and GNR.

2.Check the circuit

controller band. If required

adjust it .

3. Check the track circuit &

attend it.


.

NEALES BLOCK INSTRUMENT TROUBLE SHOOTING CHART:

No out going from X &

No incoming to X

Short L1 & L2 at test

Panel at X. check Galvo

Deflection

Short L1 & L2 at

Block counter

And Ensure Galvo

deflection.

Short L1 & L2

At instrument

Terminal

Check the outgoing

circuit from Battery

to L1&L2 &

Rectify

Check for continuity of

Incoming circuit at X

Check earth connection, if

earth return.

Break in line

Wire between

Block counter

To test panel

Break in line

Wire between

Block counter

To instrument.

Trace the incoming

Circuit, Check

Polarized Relay &

rest contact & rectify

coil.

Proceed to Y station by

Observing the Aerial line.

Short L1 & L2 at Y station

at test panel & ensure

Galvo Deflection.

Check the continuity of

incoming circuit from L1

& L2. Check earth

connections.

Trace the incoming

circuit, rest contact,

polarized relay coil &

rectify.

Inform Lineman to rectify

line fault.


.

neals token instrument

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