Indian Railway Signalling concepts and basics.pdf

It is about basic concepts of Indian Railway signalling

1. CHAPTER -1
INTRODUCTION TO RAILWAY SIGNALLING
SUBJECT IRISET-SECUNDERABAD 2

2. VARIOUS TRANSPORT SYSTEM

3. Permanent way
S.V. Rao
4

4. Railway signalling
•Railway Signal-apparatus used to provide non-
verbal, safe and precise information to driver
•Aspect-How signal appears ( Red, Yellow& Green )
•Indication-Information provided by aspect
•ON aspect-Most restrictive aspect ( RED for Stop Sig)
•OFF aspect-Other than ON aspect ( Yellow / Double
Yellow/ Green )
SUBJECT IRISET-SECUNDERABAD 5

5. ROAD SIGNAL Railway signal
SUBJECT IRISET-SECUNDERABAD 6

6. Two Aspect Lower Quadrant Signalling
ON Aspect: 0
0
to 5
0
Indication-Stop Dead
OFF Aspect: 45
0
to 60
0
Indication-Proceed
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I. Stop Signal

7. Stop DeadProceed and be prepared to
stop at the next Stop Signal
Proceed
40
0
to 45
0 85
0
to 90
0
8
0
0
to 5
0
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Upper Quadrant Semaphore Signalling
I.Stop Signal

8. Multiple Aspect Colour Light Signals
I. Stop Signal (Three aspect)
9
ProceedCautionStop
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9. 1002.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Multiple Aspect Colour Light Signals
Stop Signal (Four aspect)

10. Need for Signaling in Railways:
•Signalling in railways has evolved for the following:
•Running trains safely by securing it`s intended path.
•Handle more trains effectively.
•Unambiguous & Timely Communication to Loco
Pilot for regulating speed of train
•The Train Loco Pilot is very much dependent on the
aspect of the signal for controlling the speed of train
SUBJECT IRISET-SECUNDERABAD 11

11. Railway Signalling conveys the following
•Timely information to Loco Pilot for regulating
speed of his train.
•Information is conveyed by a signal showing various
aspects.
. Many signals are interlinked for giving advance
information.
•A signal ensures
•Physical clearance of intended path.
•Securing various points in the path.
•Closure of Level crossing gates.
•No other train is moving in this path.
SUBJECT IRISET-SECUNDERABAD 12

12. Axle with wheels
S.V. Rao
13

13. Wheel Flange
G.V Rao-ITD2
14

14. Point
G.V. Rao
15
Stock Rail, Tongue rail ( Switch rails )
STOCK RAIL

15. Points & Cross over
16

16. Individual Point
17
1676 MM

17. Point Clamp
18

18. Hand Operated Point

19. POINTS : A Mechanism provided on the track to facilitate
diversion of trains from one route to another.
(Our Engines do not have steering wheel as available in motor
cars)
Trailing Point
Facing Point
Facing Point & Trailing Point
Crossing

20. Point reverse
Sig yellow with route

21. Point normal
Sig yellow without route

22. Point.A Pt.B
X Y
ZPt.C
Pt. A for train X
Pt. B for train Y
Pt. C for train Z
Pt. B for train Z
T
F
F
T
EXAMPLE

23. Points & Signals
S.V. Rao
24

24. 25
TURNOUTS
FACING POINT
TRAILING POINT
SE4-CAVACH VER-1.0 IRISET-SECUNDERABAD

25. Station yard ( Points )
S.V. Rao
26

26. Signalling concepts
CONTROL OVER MOVEMENT OF TRAINS
Time Interval Method and
Space Interval Method
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27. •Trainscannotbesteeredawayasinthecaseofother
transports.
•Theyarerequiredtofollowoneanotherinthesame
directiononthelengthoftrack.
•Anothersetofdiversiontrackisrequiredtobeprovided
eitherforovertakingvehiclesmovinginthesamedirection
orforcrossingthevehiclesfromtheoppositedirection.
Control over movement of trains
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28. Time Interval Method-
•Different types of trains like, Express/Mail, passenger,
high-speed freight and low speed freight shunting
trains are running etc.
•The speed of all the trains are not same
•The terrain of the country is not same everywhere
•The brake power, hauling capacity, load of train is not
same for all trains; and
•The stopping places of all trains are not the same
Control over movement of trains
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29. Space Interval Method
•Inthismethodof"Controlovermovement",thelength
oftrackisdividedintosectionscalled"Blocks".
•Theentryofatrainintothe‘block’iscontrolledinsuch
awaythatonlywhenitisfree,atraincanbeallowed
toenterit.
•Thismeansthatbetweentwoconsecutivetrains,there
isadefinitespaceinterval.
Control over movement of trains
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30. •Thespaceintervalsystemusestheblockworkingwherein
theentryoftrainontotheblocksectionisjointly
controlledbytheentryandexistpointsoftheblock
section.
•Thedriverisauthorizedtoproceedintoasectionbythe
signalcontrollingtheentrytothesection.
•ThemainpurposeofRailwaySignallingSystemsisto
maintainasafedistancebetweentrainsonthesametrack.
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31. Fixed Signals: GR 3.03 to 3.51
Hand Signals: GR 3.52 to 3.58
Detonating Signals:
GR 3.59 to 3.64
Flare Signals: GR 3.65 to 3.67
SIGNALS
32T
N
A
R
D
U
A
Q
L
O
W
E
R
M
E
V
O
M
E
N
T
I N
N
I
T
N
E
M
M
O
V
E
T
A
N
U
A
D
R
Q
REP
P
U
RH
UQ
LQ
RHLH
LQ
UQ
LH 02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

32. 3302.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
TYPES OF SIGNALSNote: CLS - Colour Light Signal
Signals
Visual Audible
Voice WhistleDetonatorsFlare Signal Fixed Signal
SubsidiaryRunning
Multiple Aspect
Colour Light Signal
Movable
Flag Signal
Shunt
Signal
Calling On
Signal

33. 34
STOP:
PROCEED:
Hand Signals
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34. Hand Signals
35
Move slowly for
coupling
Move towards the
person signalling
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35. Flare Signals
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36. Detonating Signals
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37. Banner Flag
38
•Abannerflagisatemporaryfixeddangersignal,
consistingofaredclothsupportedateachendona
postandstretchedacrossthelinetowhichitrefers.
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38. Block Instruments
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39. Block Instruments
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40. CHAPTER -2
INTRODUCTION TO RULES,
MANUALS AND SPECIFICATIONS
SUBJECT IRISET-SECUNDERABAD 41

41. General and Subsidiary Rules (G&SR)
•The General Rules for Open Lines of the Railways
1976 have been framed under Section 198 of the
Railways Act 1989 by the Government of India.
•GR is common for all zonal Railways
•GR is issued by Railway Board
•The Subsidiary Rules ( SR ) and the Special
Instructions of the Zonal Railways are issued by the
Principle Chief Operations Manager, the Authorized
Officer, on the authority of GR 1.02 (5).
SUBJECT IRISET-SECUNDERABAD 42

42. Signal Engineering Manual (IRSEM)
•Signal Engineering Manual deals with items of general
nature, organization of Signal and Telecommunication
department, duties and responsibilities of Officers
and staff at various levels and general requirements
for installation of signaling equipments etc
•IRSEM Issued by Railway Board
SUBJECT IRISET-SECUNDERABAD 43

43. Telecom Manual
•This manual provides detailed guidelines for setting
up and maintaining the telecommunication
systems. This manual also gives an overview about
Organization of the Signal and Telecommunication
Department both at Headquarters and at Division.
•This manual is issued by Railway Board,
SUBJECT IRISET-SECUNDERABAD 44

44. A.C Traction Manual
The "A. C. Traction Manual" contains installation,
maintenance and operation of 25 kV/AC 50 Hz
single phase traction installations, electric
locomotives and electrical multiple units and other
connected matters including railway electrification.
•This manual is issued by Railway Board.
SUBJECT IRISET-SECUNDERABAD 45

45. Permanent way Manual
•The manual contains uniform procedures and
practices to be followed on Indian Railways by
Engineering department
•This manual is issued by Railway Board.
Block Manual
•This manual contains instructions in detail
regarding block working pertaining to that railway
•This manual is issued by Principle Chief Operations
Manager ( PCOM )
SUBJECT IRISET-SECUNDERABAD 46

46. Accident Manual
•This manual contains all the rules regarding the
class and description of accidents, accident
Enquiries and procedures for reporting accidents.
•This manual is issued by Principle Chief Operations
Manager
Schedule of Dimensions (SOD)
•The Schedule of Dimensions is meant to safeguard
the interests of both the rail users as well as the
railways and must be rigidly followed by the
railways
•This manual is issued by Railway Board.
SUBJECT IRISET-SECUNDERABAD 47

47. Indian Railway Standard Specifications
•Specifications for materials used for signalling
purposes have been drawn out by the Director
General, Research, Designs and Standards
Organisation (DG/RDSO), Ministry of Railways,
Lucknow and are titled as "Indian Railway Standard
Specifications
SUBJECT IRISET-SECUNDERABAD 48

48. •Some of the specifications are listed below
•RDSO/SPN/ 153 /2011 for LED Signals
•IRS-S-63 /2007 PVC Signalling Cables
•IS-266 for ACID
•IS 1069 for Distilled water
SUBJECT IRISET-SECUNDERABAD 49

49. •CCRS -CHIEF COMMISSIONER OF RAILWAY SAFETY, CRS
(under approved special instructions) means an
Inspector appointed to exercise any functions under
the Act, and includes a Commissioner of Railway Safety
•Authorized officer (special instructions) means
instructions issued from time to time by the
authorisedofficer in respect to particular cases or
special circumstances.
SUBJECT IRISET-SECUNDERABAD 50

50. IRISET 51MSDAC –Comparative Study Ver 1.0

51. CHAPTER -3
DEFINITIONS ( GR 1.02 )
SUBJECT IRISET-SECUNDERABAD 52

52. Definitions
53
Adequate Distance:
–means the distance sufficient to ensure safety.
Signal 1 Signal 2
For taking off Signal 1, portion shown beyond Signal 2
must also be clear. This portion is the Adequate
Distance.
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53. •INTERLOCKING-means an arrangement of signals,
points and other appliances, operated from a panel or
lever frame, so interconnected by mechanical locking
or electrical locking or both that their operation must
take place in proper sequence to ensure safety
•MULTIPLE ASPECT SIGNALLING-means a Signalling
arrangement in which signals display at any one time
any one of the three or more aspects and in which the
aspect of every signal is pre-warned by the aspect of
the previous signal or signals.
SUBJECT IRISET-SECUNDERABAD 54

54. S1 Basics of Indian Railway Signalling Ver.1.0
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Mechanical Interlocking

55. SUBJECT IRISET-SECUNDERABAD 56
RELAY INTERLOCKING

56. RELAY INTERLOCKING
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57. SUBJECT IRISET-SECUNDERABAD 58
ELECTRONIC INTERLOCKING

58. ASPECT & INDICATIONS OF MACLS
SUBJECT IRISET-SECUNDERABAD 59
ASPECT STOP CAUTION PROCEED
INDICATION STOP DEAD Proceed & be
prepared to stop
at next signal
PROCEED

59. BlockSection
Meansthatportionoftherunninglinebetweentwoblock
stationsontowhichnorunningtrainmayenteruntilLineClear
hasbeenreceivedfromtheblockstationattheotherendof
theblockstation.
Blocksection=LSS(RearStn)toFSS(AdvanceStn)+
Adequatedistance
Station
1
Station
2
Block Section
Home Signal
Adv. Starter
Block
Overlap
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60. 61
AtaclassBstationprovidedwithmanuallyoperatedMA
signals,whichisincluded-
(a)Onadoubleline-
i)Betweentheoutermostfacingpointsandthelast
StopSignalofthestationineitherdirection,or
ii)BetweentheBSLBwhereprovidedandtheLast
StopSignalofthestationineitherdirection,or
(b)Onasingleline-
i)BetweentheShuntingLimitBoardsorAdv.Strs(if
any),or
ii)Betweentheoutermostfacingpoints,ifthereare
noShuntingLimitBoardsorAdvStrs.
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Station section

61. Station Section (shown in green)
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62. StationLimits-meanstheportionofarailwaywhichis
underthecontrolofaStationMasterandissituated
betweentheoutermostsignalsofthestationorasmaybe
specifiedbyspecialinstructions.
Example:
TheStationLimitsarereckonedbetweentheDistantand
thelaststopsignalineachdirectiononsingledistant
territory
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63. BlockBack:
–MeanstodispatchamessagefromaBlockStation
intimatingtotheblockstationimmediatelyinrear
onadoublelineortothenextblockstationon
eithersideonasingleline,thattheblocksectionis
obstructedoristobeobstructed.
Station 2 Blocks
Back this line
Station 1 Station 2
Station 1 blocks
back this line
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64. Block Forward:
•MeanstodispatchamessagefromaBlockStationona
doublelineintimatingtotheblockstationimmediately
inadvancethefactthattheblocksectioninadvanceis
obstructedoristobeobstructed.
Station 1 Block
Forward this line
Station 2 blocks
Forward this line
Station 1
Station 2
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65. InRearofaSignal:meanstheterritoryoverwhichan
approachingtrainhastopassbeforereachingthesignal
location.
InAdvanceofaSignal:Atermusedindefininga
territorybeyondasignalasseenfromtheapproaching
train
In rear of signalIn advance of signal
Direction of train
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66. LineCapacity-meansthemaximumnumberoftrains
thatcanberunonanygivensectionduringacalendar
dayof24hours.
RunningTrain-meansatrainwhichhasstartedunderan
authoritytoproceedandhasnotcompleteditsjourney.
Day-meansfromsunrisetosunset.
Night-meansfromsunsettosunrise.
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67. FOULING MARK -means
the mark at which
the infringement of
fixed Standard
Dimensions occurs,
where two lines cross
or join one another.
SUBJECT IRISET-SECUNDERABAD 68
FM

68. Classification of Stations
Block Stations : Class A,
Class B,
Class C.
Non-block Stations: Class D
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69. ApprovedSpecialInstructions-meanspecial
instructionsapprovedoforprescribedbythe
CommissionerofRailwaySafety.
AuthoritytoProceedmeans-theauthoritygivento
thedriverofarunningtrainunderthesystemof
workingtoentertheBlockSectionwithhistrain.
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70. Fixed Signal
Definition:GR1.01(22)
Asignaloffixedlocationindicatingacondition
affectingthemovementofatrainandincludesfixed
lightforusebydayandfixedlightforusebynight.
MACLS–MultipleAspectColourlightsignalling
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71. TRACK CIRCUIT -means an electrical circuit
provided to detect the presence of a vehicle on a
portion of track, the rails of the track forming part
of the circuit.
SUBJECT IRISET-SECUNDERABAD 72

72. Track Circuit
Track relay
Battery
Track feed Battery
Charger
TL JB TL JB
RT
Glued joints Glued joints

73. IRISET 74MSDAC –Comparative Study Ver 1.0

74. CHAPTER -4
FIXED SIGNALS , ASPECTS &
INDICATIONS
SUBJECT IRISET-SECUNDERABAD 75

75. MACLS
Main
signals
Subsidiary
signals
Misc
signals
SE4-CAVACH VER-1.0 IRISET-SECUNDERABAD 76

76. Main
signals
Reception
signals
Distant
signals
Home
signal
Dispatch
signals
Starter &
LSS
SE4-CAVACH VER-1.0 IRISET-SECUNDERABAD 77

77. •Same aspect by Day and Night.
•Luminous signals. Do not depend on reflected light
for visibility.
•Electrical operation hence fast response
•No mechanical transmission; no moving parts; no
drooping of signals; no restriction on range of
operation.
78
MACLS -Advantages
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78. •Ahead signal aspects pre-warned by rear signals
•Long range of operation
•Better visibility of Main signals
•Maximum four aspects possible
•RG aspect at drivers eye level
•Less maintenance due to wear & tear less
SUBJECT IRISET-SECUNDERABAD 79

79. Multiple Aspect Colour Light Signals
I. Stop Signal (Three aspect)
80
ProceedCautionStop
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80. 81ASPECT & INDICATION OF MULTIPLE ASPECT COLOUR LIGHT SIGNAL
ASPECT STOP CAUTION PROCEED
INDICATION STOP DEAD PROCEED & BE
PREPARED TO STOP AT
THE NEXT STOP SIGNAL
PROCEED 18.11.2020 S1 Basics of Indian Railway Signalling Ver.1.1
Multiple Aspect Colour Light Signals
Stop Signal (Three aspect)

81. 8202.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Multiple Aspect Colour Light Signals
Stop Signal (Four aspect)

82. ASPECT STOP CAUTION PROCEED
INDICATION STOP
DEAD
PROCEED & BE PREPARED TO
STOP AT THE NEXT STOP SIGNAL
PROCEED
ASPECT & INDICATION OF MACLS
SE4-CAVACH VER-1.0 83IRISET-SECUNDERABAD

83. 8402.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Multiple Aspect Colour Light Signals
Stop Signal (Four aspect)

84. ASPECT STOP CAUTION ATTENTION PROCEED
INDICATION STOP DEAD PROCEED & BE PREPARED
TO STOP AT THE NEXT
STOP SIGNAL
Proceed &be prepared to
pass next stop signal at
restricted speed
PROCEED
ASPECT & INDICATION OF MULTIPLE FOUR ASPECT COLOUR LIGHT SIGNAL
SE4-CAVACH VER-1.0 85IRISET-SECUNDERABAD

85. 02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0 86Yellow
P P P
Yellow
Yellow
Green
Multiple Aspect Colour Light Signals
Distant Signal
ASPECT Caution Attention Proceed
INDICATION
Proceed & be
prepared to stop at
next Stop Signal
Proceed & be prepared to pass next
Stop Signal at such speed as
prescribed by special instruction
Proceed

86. Multiple Aspect Colour Light PermessiveSignal
P P P
SE4-CAVACH VER-1.0 IRISET-SECUNDERABAD 87

87. Symbols used to show Signals
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88. IRISET 89MSDAC –Comparative Study Ver 1.0

89. CHAPTER -5
DESIGNATION OF SIGNALS
SUBJECT IRISET-SECUNDERABAD 90

90. Fixed Signals
Multiple Aspect Colour Light
Signals
91

91. Signals at Stations
Multiple Aspect Signals:
Reception Signals:
•Distant
•Inner distant
•Home ( FSS )
Dispatch Signals:
•Starter
•Intermediate Starter
•Advanced Starter ( LSS )
GR3.07(6)covers
theprovisionof2
DistantSignals.
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92. Multiple Aspect Colour Light Signals
I. Stop Signal (Three aspect)
93
ProceedCautionStop

93. Multiple Aspect Colour Light Signals
94
I. Stop Signal (Four aspect)

94. Multiple Aspect Colour Light Signals
II.Distant Signal
P P P
95

95. Calling On signals
96
‘C’ Marker
Driver to obey
Calling On Signal

96. Position Light Type shunt signal
97
ON ASPECT OFF ASPECT

97. Flare Signals
98

98. Advance Starter or SLB or BSLB
•AtclassBsinglelinestations:
•ASorSLBrequiredifobstructingoflineoutsideHomeistobe
permitted.
•DistancebetweenASorSLBandopposingFSSshallnotbeless
than400m(for2aspect)or180m(forMA)
•AtclassBdoublelinestations:
•BSLBonlyforMA
•Onlywheretherearenopointsoroutermostpointsat
approachingendaretrailing
•Locatednotlessthan180minadvanceofHomeandprotects
outermosttrailingpoints,ifany
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99. 10002.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0BLOCK
SECTION
LIMIT BOARD
SHUNTING
LIMIT BOARD
Block Section Limit Board and Shunting Limit Board

100. IRISET 101MSDAC –Comparative Study Ver 1.0

101. CHAPTER -6
SUBSIDIARY SIGNALS, INDICATORS &
MARKERS
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102. Calling –ON Signal
103
Subsidiary Signals
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103. Subsidiary signal ( Shunt sig )
SUBJECT IRISET-SECUNDERABAD 104

104. Subsidiary Signals
105
•Signals which control movement of trains within the
Station Section are :-
–Shunt signals
–Calling-on Signals
And are called as Subsidiary Signals
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105. Special features of Subsidiary signals
106
•Thesesignalsauthorizemovementatslowspeeds
only.
•Movementiswithinthestationarea.
•Unlikerunningsignals,theymayauthorizemovement
ontooccupiedlines.
•Visibilityofsignalsisnotcritical.
•Pre-warningisnotrequired.
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106. Shunt Signal (GR3.14)
107
•Usedforshuntingwithinthestationyard,Movementis
authorizedatsuchslowspeedastobeabletostopshortof
anyobstruction
•GR5.13(3):Thespeedduringshuntingoperationsshall
notexceed15kmphunlessotherwiseauthorizedbyspecial
instructions
•Canbeonapostbyitselforbelowastopsignal(except
theFirstStopSignal)
•Morethanoneshuntsignalmaybeplacedonthesame
post
•Whentakenoff,itauthorizesthedrivertodrawahead
eventhoughtheStopsignalaboveitmaybeOn
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107. Subsidiary signal ( Shunt Sig )
SUBJECT IRISET-SECUNDERABAD 108

108. 109
Shunt signal when taken 'OFF' authorises the driver to
draw ahead with caution even though the stop signal, if
any, above it is at 'ON' position,
The shunt signal shall be
•Position Light Shunt Signals.
When a Shunt Signal is placed below a Stop Signal, it shall
show no light in the "ON“ position.
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SHUNT SIGNALS (GR 3.14)

109. Shunt below starterIndependent shunt signal
SUBJECT IRISET-SECUNDERABAD 110

110. Calling On signal
111
•Have no independent existence
•Provided below Stop Signal governing approach of
train expect Last Stop Signal
•C-Marker should be provided
•Train can be received on occupied line
•Train movement with in station section only
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111. Calling On signal in CLS
112
‘C’ Marker
Driver to obey
Calling On
Signal
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112. SUBJECT IRISET-SECUNDERABAD 113
Calling –ON signal below starter signal

113. Indicators and Markers
114
IndicatorsandMarkersareprovidedoncertain
signalsorpointstoprovideextrainformation
totheDrivers.
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114. Indicators and Markers on MACLS
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115. Markers on Colour Light Signal Posts
116
R
C
P
A
IB
A
Auto Signal
Semi
Auto Signal
Permissive
Signal
Intermediate
Block Signal
Calling-On
Signal
Repeating
Signal
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116. Markers on Colour Light Signal Posts
117
A G AAG
Gate Signal in
Auto Territory
Gate Signal in Semi Auto
Territory when interlocked
with Points also
G
Gate Signal
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A AAG

117. Gate Stop Signal
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118. 11902.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Distant Signal

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Calling-ON Signal

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Automatic Signal

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Semi Automatic Stop Signal
A

122. 12318.11.2020 S1 Basics of Indian Railway Signalling Ver.1.1
Gate stop Signal in Automatic Territory
A

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Gate Stop Signal in Automatic Territory
AA
A
AG

124. 125
Pointsarecorrectlyset,
lockedLCgateisclosed
properlyandsignalis
workingasAutomatic
Signal
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Gate Stop Signal in Automatic Territory
A

125. 126
LCgateisdefectivebut
pointsarecorrectlyset,
lockedandsignalis
workingasGatestop
Signal
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Gate Stop Signal in Automatic Territory
AG

126. Point Indicator
127
Theyshowawhite
target(duringday)ora
whitelight(during
night)in both
directionswhenpoints
aresetforstraight&
notargetorgreenlight
whensetforturnout.SET FOR
STRAIGHT
SET FOR
TURNOUT
TARGET TYPE POINT INDICATOR
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Pointindicatorsareappliancesfittedtopointsto
indicatethepositioninwhichthepointsareset.

127. 128
Trap Indicators
Trapindicatorsare
appliancesfittedto
Trappointsto
indicatetheposition
inwhichtheyareset.
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128. Trap Indicators
129TRAP OPEN
OR
DERAIL ON
TRAP CLOSED
OR
DERAIL OFF
TARGET TYPE TRAP INDICATOR
Theyshowared
target(duringday)or
aredlight(during
night)inboth
directionswhentrap
pointsareopen&
notargetorgreen
lightwhentrappoints
areclosed.
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129. Route Indicators
130
Acommonsignalwithroute
indicatorisprovidedinlieuof
separatesignalsonabracketed
postoragantry.
A Route indicator may be of :
◦Stencil type
◦multi-lamp type
◦junction type
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130. 18.11.2020 S1 Basics of Indian Railway Signalling Ver.1.1 131
DIRECTIONAL TYPE
ROUTE INDICATOR
MULTI LAMP TYPE
ROUTE INDICATOR
STENCIL TYPE
ROUTE INDICATOR
[For any speed ] [Speed up to 15 kmph][Speed up to 15 kmph]
Route Indicators

131. 13202.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0BLOCK
SECTION
LIMIT BOARD
SHUNTING
LIMIT BOARD
Block Section Limit Board and Shunting Limit Board

132. 13302.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Goodswarning Board
Passenger warning Board

133. 13402.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0T
P
10
10
S
Caution
Indicator
Termination
Indicator
Speed
Indicator
'S' Marker
Board
Various Indicators used by permanent way Department

134. 135 02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

135. 136 02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

136. 137 02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

137. IRISET 138MSDAC –Comparative Study Ver 1.0

138. CHAPTER -7
OVERLAPS ( SIG &
BLOCK OVERLAPS)
SUBJECT IRISET-SECUNDERABAD 139

139. Adequate distance
140
•GR1.02(2),AdequateDistancemeansthedistance
sufficienttoensuresafety.
•Thisisthelengthoftrackinadvanceofasignal
whichmustbekeptclearbeforethesignalnextin
rearcanbetakenoff.
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140. Adequate distance (contd.)
141
Conditions for taking off Stop Signals -
GR3.40:TheHomesignalshallnotbetakenoffunless,
Onadoublelinethelineisclearforanadequate
distancebeyondthestarter,or
Onasingleline,lineisclearforanadequatedistance
beyondthetrailingpoints.
(exceptataterminalstationorunlessthetrainhasbeen
broughttoastopinrearofit)
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141. GR3.42:TheLSSorIBSshallnotbetakenOFFforatrain
unlessLineClearhasbeenobtainedfromtheblockstation
inadvance.
GR8.01(1)(b)&(c):SuchLineClearshallnotbegiven
unlessthelineisclearnotonlyuptotheFSSbutalsoforan
adequatedistancebeyondit.
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142. 14302.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0BLOCK SECTION
BLOCK OVERLAP
ACTUAL ROUTE OF LSS OF STN 'A'
STN 'A'
RUNNING LINE
STN 'B'
LSS OF STN 'B'
LSS OF
STN 'A'
FIRST STOP
SIGNAL OF STN 'B'
PORTION OF TRACK TO BE KEPT CLEAR BEFORE
"LINE CLEAR IS GIVEN BY STN 'B' TO STN 'A'
P
DISTANT
SIGNAL

143. GR9.01(c)(i):Theautomaticsignalshallnotassume
offaspectunlessthelineisclearnotonlyuptothenext
Stopsignalinadvancebutalsoforanadequatedistance
beyondit
AStopSignalshallnotdisplayOffaspectunlesstheline
isclearnotonlyuptothenextstopsignalbutalsoan
adequatedistancebeyondit.
Adequate distance (contd.)
14418.11.2020 S1 Basics of Indian Railway Signalling Ver.1.1

144. OVERLAP
OVERLAP-means the length of track in advance of a stop
signal (S2), which must be kept clear, either for clearing
the stop signal next in rear (S1)or for the purpose of
granting permission to approach.
S1
Route of signal S1
S2
Overlap of S1

145. SUBJECT IRISET-SECUNDERABAD 1461.4 km
OBSTRUCTION
S.O = 180 mts
(a) SIGNAL OVERLAP IN 2-ASPECT
(b) SIGNAL OVERLAP IN M.A.S.
S.O = 120 mts
OBSTRUCTION
OBSTRUCTION
B.O = 180 mts
(d) BLOCK OVERLAP IN M.A.S.
(c) BLOCK OVERLAP IN 2-ASPECT
B.O = 400 mts
OBSTRUCTION
1 km
BA
1 km
PASSENGER
WARNING BOARD
FIRST STOP
SIGNAL
DISTANT
SIGNAL
FIRST STOP
SIGNAL
GOODS WARNING
BOARD
P 1.4 km
OBSTRUCTION
S.O = 180 mts
(a) SIGNAL OVERLAP IN 2-ASPECT
(b) SIGNAL OVERLAP IN M.A.S.
S.O = 120 mts
OBSTRUCTION
OBSTRUCTION
B.O = 180 mts
(d) BLOCK OVERLAP IN M.A.S.
(c) BLOCK OVERLAP IN 2-ASPECT
B.O = 400 mts
OBSTRUCTION
1 km
BA
1 km
PASSENGER
WARNING BOARD
FIRST STOP
SIGNAL
DISTANT
SIGNAL
FIRST STOP
SIGNAL
GOODS WARNING
BOARD
P

146. 147
Type of signal
SignalsMACLS Automatic signaling
on double line
Automatic
signaling
on single
line
Signal
overlap
120 Mtrs.
120 Mtrs. 120 Mtrs.
Block
overlap
180 Mtrs. --- -----
Overlaps
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147. Sand hump
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148. IRISET 149MSDAC –Comparative Study Ver 1.0

149. 150
CHAPTER -8 & 9
Braking Distance, Sighting Distance &
Visibility of Signals
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150. Braking Distance
151
•Thedistancetravelledbyatrainafteritsbrakesare
appliedisknownastheBrakingDistance.
•Whennormalorservicebrakesareapplied(shutting
offpowerandgradualapplicationofbrakes),thedistance
travellediscalledServiceBrakingDistance(SBD).
•Whenemergentbrakesareapplied(shuttingoffpower
andfullapplicationofbrakes),thedistancetravelledis
calledEmergencyBrakingDistance(EBD).
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151. Braking Distance
152
•Brakingdistanceisafunctionofspeed,brakepower,
gradient,conditionandtypeofrollingstock,condition
ofrails,curvature,windspeedetc.
•Sincethesefactorsaredifficulttoassess,trialsare
conductedbyRDSOtodeterminetheEBDsofdifferent
typesoftrains,locomotivesetc.atvariousspeedsand
resultsarepublishedandcirculatedperiodically.
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152. Sighting Distance
153
•Sightingdistance-isthedistanceoverwhichthemost
restrictiveaspectofasignalisvisiblefromthe
locomotivecab.
•Everysignalmustbesolocatedastoprovidethe
minimumSDnecessaryforit.
•Aftersightingasignal,thedriverreactstoitandthen
appliesbrakes(ifrequired).
•ReactionDistance(RD)-isthedistancetravelledbythe
trainduringthistime.Therefore,SDshouldbeequalto
ormorethanRD+EBD.
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153. Sighting Distance for FSS
154
•For 2 aspect signals, since there is no pre-warning,
SD = RD + EBD
•For multi aspect signals, since there is pre-warning,
SD=RDonly(becauseEBDisavailablebetween
thesightedsignalandthenextsignalwherethetrainmay
havetostop).
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154. Visibility of Signals
MULTIPLE ASPECT SIGNALS
•Distant Signal 400 Metres
•Inner Distant Signal200 Metres (where provided)
•All Stop Signals200 Metres
•Subsidiary signals -Visibility is not a criteria
Ifitisnotpossibletoensure200Metres(7to8
seconds)continuousvisibilityofanystopsignalwhile
approachingit,asuitablespeedrestrictionshallbe
imposed.
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155. IRISET 156MSDAC –Comparative Study Ver 1.0

156. CHAPTER –10 & 11
Isolation & Simultaneous Reception
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157. ISOLATION
•ISOLATION-meansanarrangement,securedby
thesettingofpointsorotherapprovedmeans,to
protectthelinesoisolatedfromthedangerof
obstructionfromotherconnectedlineorlines.

158. Isolation: Requirements
159
GR 4.11 Limits of speeds while running through stations
(1)Notrainshallrunthroughaninterlockedstationata
speedexceeding50kmph...unlessthelineonwhich
thetrainistorunhasbeenisolatedfromallother
linesbythesettingofpointsandinterlockingissuch
astomaintainthisconditionduringthepassageof
thetrain.
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159. Isolation required
•A line on which train movements at speeds higher
than 50 kmphare permitted should be isolated
from all connected lines.
•Passenger lines should be isolated from all
connected goods lines and sidings, whatever the
speed may be.
SUBJECT IRISET-SECUNDERABAD 160

160. •The isolation of goods reception lines from sidings
is considered desirable.
•It is not necessary to isolate one goods reception
line from another goods or one passenger line from
another passenger line when dealing with speeds
of 50 kmphand less.
SUBJECT IRISET-SECUNDERABAD 161

161. 162
-Meansofisolation
Isolationmaybeaccomplishedby-
–(a) connection to another line or long siding;
–(b) the provision of short dead end siding; or
–(c) the provision of trap
–( d ) Slip siding
–( e) Catch siding
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162. Siding, Dead End, Single Derailing Switch
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163. When point is in normalthen cross
movement is not possible
When point is in normal ORin
reveres position then cross
movement is always possible
from line I to line II
Line I
Line II
Line II
Line I
Hence line I and line II canbe isolated
Hence line I and line II cannotbe isolated
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

164. Derailing Switch, Dead End, Sand Hump
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165. SLIP SIDING & CATCH SIDING
•For all gauges the maximum gradient permitted within
the station yardis 1:1200 .
•If steeper gradients are available in close proximity of
station yard then special type siding are provided.
•"SLIP SIDING" has to be provided, where the gradient
steeper than 1:100& falling away from the station.
•SLIP SIDINGprotects block section,
•Prevents un authorisedentry of vehicles into the next
block section.

166. •“CATCH SIDING” provided where the gradient steeper than
1:80 & falling towards the station.
•CATCH SIDINGprotects station section.
•Prevents un authorisedentry of vehicles into station &Trap
uncontrolled vehicles coming from the block section
•"Slip siding" and `catch siding' points must be interlocked
with the block instruments,
•Normally point of such sidings should set for siding &
should not be used for shunting or stabling purposes.
SUBJECT IRISET-SECUNDERABAD 167

167. Slip Siding
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168. Catch Siding
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169. Simultaneous Reception -GR 3.47
170
Takingoffsignalsformorethanonetrainatatime-
Whentwoormoretrainsareapproaching
simultaneouslyfromanydirection,thesignalsforone
trainonlyshallbetakenoff,othernecessarysignals
beingkeptaton,untilthetrainforwhichthesignals
havebeentakenoffhascometoastandatthestation
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170. Simultaneous Reception
171
GR5.16Shuntingduringreceptionoftrains-When
signalshavebeentakenoffforanincomingtrainon
toalinewhichisnotisolated,noshuntingmovement
shallbecarriedouttowardspointsoverwhichthe
incomingtrainistopass.
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171. Simultaneous Reception
17202.06.2020
S1 Basics of Indian Railway Signalling Ver.1.0
Line 1
Line 2 (Main Line)
Line 3
UNIVERSAL

172. POINT NORMAL
POINT NORMAL
POINT REVERSE
POINT REVERSE
Overlap
Overlap
If Over shoots
SIMULTANEOUS RECEPTION IS POSSIBLE

173. POINT NORMAL
POINT NORMAL
POINT NORMAL
POINT REVERSE
Overlap
Overlap
If Over shoots
SIMULTANEOUS RECEPTION IS NOT POSSIBLE

174. 175 02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Sand Hump

175. 176 02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Sand Hump

176. SIMULTANEOUS RECEPTION & DISPATCH
•Taking OFF reception signal and dispatch signal for
different trains at the same time is called
simultaneous dispatch of trains.
•For simultaneous reception and dispatch of trains,
isolation and separate overlap for each movement is
ensured.

177. POINT NORMAL
POINT NORMAL
POINT NORMAL
POINT REVERSE
Overlap
SIMULTANEOUS RECEPTION & DISPATCH IS POSSIBLE

178. POINT NORMAL
POINT NORMAL
POINT NORMAL
POINT REVERSE
Overlap
SIMULTANEOUS RECEPTION & DISPATCH IS NOT POSSIBLE
No separate
Overlap

179. IRISET 180MSDAC –Comparative Study Ver 1.0

180. CHAPTER -12
SYSTEMS OF TRAIN WORKING
SUBJECT IRISET-SECUNDERABAD 181

181. Systems of Train working
182
Chapter VII of GR describes the Systems of working
Systems of Train working:
The Absolute Block System,
The Automatic Block System,
The One Train Only System.
The Following Trains System,
The Train-staff and Ticket System, and
The Pilot Guard System
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

182. The Absolute Block System
183
Essentials(GR8.01):
NotrainshallleaveaBlockStationunlessLChasbeenreceived
fromBlockStationinadvance
Ondoubleline,suchLCshallnotbegivenunless
Thewholeofthelastprecedingtrainhasarrived
complete
AllnecessarysignalshavebeenputbacktoOnbehind
thesaidtrain,andlineisclearup-toFSSplusadequate
distancebeyondit
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183. •Unless otherwise approved under "approved
special instructions" ( sanction of Commissioner of
Railway Safety) block overlap shall not be less than
180 Mtsin MACLS
SUBJECT IRISET-SECUNDERABAD 184

184. The Absolute Block System
185
Onsingleline,suchLCshallnotbegivenunless
Thewholeoflastprecedingtrainhasarrived
complete
Allnecessarysignalshavebeenputbacktoonbehind
thesaidtrain
lineisclearup-toFSSplusadequatedistanceanditis
clearoftrainsrunningtowardsthestationtowhich
LCisbeinggiven.
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185. Station A
Station BBlock section Block overlap
Block section
Block overlap
P
P
FSS of Stn B
FSS of Stn A
LSS of Stn B
LSS of StnA
Dist. of Stn B
Dist. of Stn A

186. The Automatic Block System
187
Essentialsfordoubleline(GR9.01):
Linemustbecontinuouslytrackcircuited
LinebetweenstationsisdividedintoAutomaticBlock
SignallingSections
EntryintoeachSectioniscontrolledbyMACLstopsignals
TrackCircuitscontroltheaspectofsignals
OFFaspectonlywhenlineisclearup-tonext
signalplusoverlap(120m)
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

187. The Automatic Block System
188
Essentials for single line (GR 9.03):
Line must be continuously track circuited
Direction of traffic only after LC has been obtained from
station in advance
Train to start from the station only after direction of traffic
has been established
LC shall not be granted unless line is clear up-to FSS plus
overlap
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188. The Automatic Block System
189
Essentials for single line (GR 9.03):
Line between stations is divided into Automatic Block
Signalling Sections
Entry into each Section is controlled by MACL stop signals
Track Circuits control the aspect of signals
OFF aspect only when line is clear up-to next
signal
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189. The Automatic Block System
190
Aspect Control:
Yellow when one signallingsection plus overlap is clear
Green when two signallingsections plus overlap is clear (in 3
aspect territory)
Double Yellow when two signallingsections plus overlap is
clear (in 4 aspect territory)
Green when 3 signallingsections plus overlap is clear (in 4
aspect territory)
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

190. SUBJECT IRISET-SECUNDERABAD 191S.O
G
BLOCK
2
G
BLOCK
G G
S.O S.OS.O
1 3 4
BLOCK
R GG G
Y GR G
G
Y
Y R
R GY Y
Y Y
FOR SIGNAL.1. TO ASSUME YELLOW - LINE MUST BE CLEAR FOR ONE BLOCK AND ONE OVERLAP
FOR SIGNAL.1. TO ASSUME DOUBLE YELLOW - LINE MUST BE CLEAR FOR TWO BLOCKS AND ONE OVERLAP
FOR SIGNAL.1. TO ASSUME GREEN - LINE MUST BE CLEAR FOR THREE BLOCKS AND ONE OVERLAP

191. The Automatic Block System
192
Minimum equipment of signals (GR 9.04)
Manual stop signals at stations
Home
Starter
an Automatic stop signal in rear of Home signal of the station
one or more additional auto signals in between block
stations (GR 9.05)
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192. The Automatic Block System
193
Points to remember:
Track is continuously track circuited
Signals display Off aspect normally when there are no trains
Signals are replaced automatically to on with the passage of
trains past them
Drivers are authorisedto pass automatic signals after
observing certain precautions
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193. The Automatic Block System
194
WhathappensifanAutomaticsignalisdefective:
SignalcanbeatONduetoTCfailureorsomeotherdefect
Drivershouldstopandwaitinrearofsignal
oneminuteduringDAY
TwominutesduringNIGHT
IfsignalremainsON,informGuardbywhistlecode&hand
signalandproceedatrestrictedspeed(15kmphorless)till
hereachesthenextsignal,thenbeguidedbytheaspectof
nextsignal
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

194. Modified Semi-Automatic SignallingWorking
a.Under special instructions, one of the automatic
stop signals between two stations in the
automatic block signallingterritory on Double
Line may be made as modified semi-automatic
stop signal in each direction.
SUBJECT IRISET-SECUNDERABAD 195

195. •During abnormal conditions like fog, bad weather
impairing visibility, Modified Semi-Automatic Signal
may be worked by extinguishing ‘A’ marker in the
manner prescribed under special instructions and this
section shall also ensure that the ‘A’ Marker of the
Advanced Starter Signal of the station in rear and Home
signal of the station in advance shall also be
extinguished. (Provisions as per para9.01 of GR shall be
ensured.)
SUBJECT IRISET-SECUNDERABAD 196

196. SUBJECT IRISET-SECUNDERABAD 197
MODIFIED SEMI-AUTOMATIC SIGNAL

197. Markers on Automatic signal
•Each Automatic Stop
Signal shall be
identified by its number
and provided with a
Marker consisting of a
white disc with letter ‘A’
in black.
SUBJECT IRISET-SECUNDERABAD 198

198. Marker on Semi-Automatic sig
•A Semi-Automatic Stop
Signal shall be provided
with a Marker which shall
show a white illuminated
letter ‘A’ against a black
background when the
signal works as an
Automatic Stop Signal.
SUBJECT IRISET-SECUNDERABAD 199

199. •Signal interlocked with a
level-crossing shall be
provided with an enamelled
yellow disc with letters 'G'
in black and an 'A' marker
light. The 'A' marker shall
be lit only when the gates
are closed and locked
against road traffic.
SUBJECT IRISET-SECUNDERABAD 200

200. •Auto signal interlocked
with LC Gate and point
SUBJECT IRISET-SECUNDERABAD 201

201. •Points are correctly
set, locked LC gate is
closed properly and
signal is working as
Automatic Signal
SUBJECT IRISET-SECUNDERABAD 202

202. •LC gate is defective but
points are correctly set,
locked and signal is
working as Automatic
Signal
SUBJECT IRISET-SECUNDERABAD 203

203. IRISET 204MSDAC –Comparative Study Ver 1.0

204. CHAPTER 13
CLASSIFICATION OF STATIONS –A,B & C
SUBJECT IRISET-SECUNDERABAD 205

205. Classification of stations
206
1.Stationsshall,forthepurposeoftheseRules,bedividedinto
twocategories
•Block Stations, and
•Non -Block stations.
2.BlockstationsarethoseatwhichtheDrivermustobtainan
authoritytoproceedunderthesystemofworkingtoenterthe
blocksectionwithhistrain;andundertheabsoluteBlock
Systemconsistofthreeclasses-
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

206. Classification of Stations
Station
Block Station Non Block Station
Driver must obtain an authority to
proceed enter the block section
with his train
Class A
Class B
Class C
Class D
Stopping Places between
two consecutive block
stations ( do not form
boundary of any block
station)
Any station which cannot be worked under A, B,C or D class conditions:
Special Class: (MUST HAVE THE APPROVAL OF CRS: Commissioner
Railway Safety)

207. Classification of stations
208
ClassAstations-ConditionsforgrantingLineClearata
class`A`station—
•At a class `A` station on single line or double line, the line
shall not be considered clear and Line Clear shall not be
given, unless--
(a) the whole of the last preceding train has arrived
complete ;
(b) all signals have been put back to ‘on’ behind the said
train;
(c) the line on which it is intended to receive the
incoming train is clear up to the Starter and
•
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

208. (d) all points have been correctly set and all facing
points have been locked for the admission of the
train on the said line.
( e ) where Line Clear may not be given for a train
unless the line on which it is intended to receive
the train is clear for at least 400 meters beyond the
Home signal, or uptothe Starter;
SUBJECT IRISET-SECUNDERABAD 209

209. Conditions for granting Line Clear at a class ‘B’
station.––
•At a class ‘B’ station on double line, the line shall
not be considered clear and Line Clear shall not be
given, unless -
(a) the whole of the last preceding train has arrived
complete
•All necessary signals have been put back to ‘on’
behind the said train; and
(b) the line is clear -
•(i) at stations equipped with multiple-aspect
signaling -Up to the outermost facing points or the
Block Section Limit Board (if any)
SUBJECT IRISET-SECUNDERABAD 210

210. •At a class ‘B’ station on single line, the line shall not
be considered clear and Line Clear shall not be
given, unless –
(a) the whole of the last preceding train has arrived
complete;
(b) all necessary signals have been put back to ‘on’
behind the said train; and
•(c) the line is clear-up to the Shunting Limit Board
or Advanced Starter (if any ) at the end of the
station nearest to the expected train, or
•up to the outermost facing points if there is no
Shunting Limit Board or Advanced Starter.
SUBJECT IRISET-SECUNDERABAD 211

211. •At a class ‘C’ station on single line or double line in
multiple-aspect signalling, the line shall not be
considered clear and Line Clear shall not be given,
unless-
•(a) the whole of the last preceding train has passed
complete at least 400 meters beyond the Home
signal and is continuing its journey ; and
•(b) all signals taken ‘off’ for the preceding train
have been put back to ‘on’ behind the said train:
•Provided that on a single line, the line is also clear
of trains running in the opposite direction towards
the block hut from the block station at the other
end.
SUBJECT IRISET-SECUNDERABAD 212

212. ClassDstationsorNon-blockstationsarestopping
placeswhicharesituatedbetweentwoconsecutive
blockstations,anddonotformtheboundaryof
anyblocksection.
SUBJECT IRISET-SECUNDERABAD 213

213. Equipment of signals
214
Manually operated Multi aspect signals (GR 3.27)
Class of
Station
Minimum
Equipment
Additional
Equipment
A
B
Does not exist
Distant, Home, Starter
Distant, Home
Adv Str / SLB
C
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214. Comparison between class A & B stations
215
A’classstations
•Existonlyin2aspect
signalling.
•Now obsolete. Used only
under special circumstances.
•There is no station section.
•No shunting after LC is given.
•LC cannot be given to both
sides simultaneously.
•LC cannot be given unless
reception line is clear.
•Obstruction is protected by 2
signals
B’classstations
•Existin2aspectaswellasin
multi-aspectsignalling
•MoststationsareBclass,
moretrainscanbedealt
•Thereisadefinitestation
section
•Shuntingispossible.
•Nosuchrestriction.
•Nosuchrestriction.
•Obstructionisprotectedby
onesignal.
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215. IRISET 216MSDAC –Comparative Study Ver 1.0

216. CHAPTER -14
STANDARDS OF INTERLOCKING
SUBJECT IRISET-SECUNDERABAD 217

217. 21802.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Standards of Interlocking

218. SUBJECT IRISET-SECUNDERABAD 219
Para No: 7.8.9of IRSEM (Issue -July 2021): Table-3: Important Minimum Signalling Features
DETAILS STD I STD II STD III STD IV
Maximum
permissiblespeed
Up to 50KmphUp to 110KmphUp to 140KmphUp to 160Kmph
Isolation SeeNotes
below
Required Required Required
Point Operation,
Locking & Detection
Point MachinePoint MachinePoint MachinePoint Machine &
Direct Clamp type
with Thick web
switches
Train Detection
(Track circuit/Axle
Counters)
On all Run
through Lines
On all Running
Lines
On all Running
Lines
On all Running
Lines
MACLS
Signalling,Movemen
tauthority
MACLS MACLS MACLS MACLS,
Movement
Authority
Block Working
(Absolute/Automati
c Signaling)
Permitted
(Including
Token
Working)
Permitted
(Excluding Token)
Permitted
(ExcludingToken)
Or
4A Automatic
Signalling
Permitted
(ExcludingToken)
Or
4A Automatic
Signalling

219. SUBJECT IRISET-SECUNDERABAD 220
7Double
Distant/Automatic
Signalling
Not
Compulsory
Required
(On sections where
Trains have a
Emergency Braking
Distance of more
than 1 Km)
Required
Or
4A Automatic
Signalling
Required
Or
4A Automatic
Signalling
8Last Vehicle
verification
Not
Compulsory
Required at
stations with
centralized
operation or in high
density routes
Required Required
9Relay/Electronic
Interlocking (RI/EI)
RI/EI RI/EI RI/EI RI/EI
10Mobile Train radio
communication
(MTRC) or LTE or any
other Technology
Not
Compulsory
Desirable Desirable Required
11ATP
(ETCS/TCAS/TPWS)
with Cab Signalling
for SPAD mitigation
Not
Compulsory
Desirable Desirable Required
12Centralised Traffic
Control (CTC)
Not
Compulsory
Desirable Desirable Desirable

220. 1.Isolation: Isolation is not compulsory. Extract
from “Rules for Opening of Railway Lines –Rule
36” is given below
2. At no station at which isolation has not been
provided through running trains shall be permitted
unless the conditions laid down in the second
paragraph of the rule 4.11 of the General Rules are
complied with.
SUBJECT IRISET-SECUNDERABAD 221

221. •Extract of GR 4.11. Limits of speed while running through
stations.-
•No train shall run through an interlocked station at a speed
exceeding 50 kilometers an hour or such less speed as may be
prescribed by approved special instructions unless the line on
which the train is to run has been isolated from all other lines
by the setting of points or other approved means and
interlocking is such as to maintain this condition during the
passage of the train.
SUBJECT IRISET-SECUNDERABAD 222

222. •In every case in which trains are permitted to run
through on a non isolated line , all shunting shall
be stopped and no vehicle unattached to an engine
or not properly secured in accordance with General
Rule 5.23 may be kept standing on a connected
line which is not isolated from the through line.
SUBJECT IRISET-SECUNDERABAD 223

223. •All Passengers running Lines shall be isolated from all Goods
lines or Sidings connected thereto.
•All goods running Lines may be isolated from all sidings
connected there to.
•It is not necessary to isolate one goods receiving line from
another
SUBJECT IRISET-SECUNDERABAD 224

224. IRISET 225MSDAC –Comparative Study Ver 1.0

225. CHAPTER -15
OPERATION OF POINTS
SUBJECT IRISET-SECUNDERABAD 226

226. OPERATION OF POINTS
02.06.2020 227S1 Basics of Indian Railway Signalling Ver.1.0

227. Electrical point operation
SUBJECT IRISET-SECUNDERABAD 228

228. Point in general
1.Points, which are used to divert trains from one line to the
other, will become a source of danger unless adequate
precautions are taken, points are said to be facing when
they are approached from the toe end.
2.Even a casual study of points will indicate that for
movements in the facing direction more precautions should
be taken.
3.The points should be correctly set, i.e., the closed switch
should be housed correctly against the stock rail and the
open switch should be well clear of the corresponding stock
rail.
4.The points should be prevented from becoming unlocked
during the passage of a train.
02.06.2020 229S1 Basics of Indian Railway Signalling Ver.1.0

229. Location of point and range of operation
1.Pointsmustbesolocatedthatmovementsoverthemshall
bewithintheviewofthecabinorotherlocationfromwhich
theyareworked,unlessanapprovedalternativefordirect
visionbycabinman,e.g.,electricindication,isprovided.
2.Thedistanceatwhichpointsmaybeworkedbyroddingis
mustnotexceed320mexceptwherethestrokeatthelever
tailisnotlessthan200mminwhichcasetheabovedistance
maybeincreasedto460m
02.06.2020 230S1 Basics of Indian Railway Signalling Ver.1.0

230. 02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Speed of train over point
1.Pointsinwhichtheonlyequipmentisagaugetieplateanda
padlockforlockingtheminposition,andwhichmayormaynot
belocallyoperatedaresaidtobeun-interlocked.
2.Aspeedrestrictionof15KMPHisimposedovertheminthe
facingdirectionandof50KMPHinthetrailingdirection.
3.Unrestrictedspeedinthetrailingdirectionis,however,
permittedonthestraightroadifthepointsareinterlockedwith
signals,eventhoughlockinganddetectionarenotprovided.
231

231. Points & Signals
S.V. Rao
232

232. IRISET 233MSDAC –Comparative Study Ver 1.0

233. CHAPTER -16
INTER CABIN CONTROL
SUBJECT IRISET-SECUNDERABAD 234

234. CABIN
SUBJECT IRISET-SECUNDERABAD 235

235. LEVER FRAME
SUBJECT IRISET-SECUNDERABAD 236

236. INTERLOCKING
SUBJECT IRISET-SECUNDERABAD 237

237. Principles of Slotting:
•The term `Slotting' has come to mean in signallingparlance the
control of a signal by source or sources other than the operating
source.
•The control of signals by more than one source is much more
frequent than in the use of points.
•A slotted signal cannot be taken `OFF' unless the controls from
all remote locations have been operated, but it should be
possible for any one of the controlling agencies to replace the
signal to its most restrictive aspect.
INTER CABIN CONTROL
02.06.2020 238S1 Basics of Indian Railway Signalling Ver.1.0

238. The purpose of slotting is two fold:
•Toensurethatthepointslocatedonthelinecontrolledbythe
signalincludingtheoverlaparesetcorrectlyandfacingpoints
lockedandthelineisclear,beforethesignalistakenoffand
•Theseconditionsaremaintaineduntilthetrainmovementis
completed.
•Inotherwords,nootherconflictingorfoulingmovementis
allowedtotakeplaceandthepointsarenotaltereduntilthe
trainmovementiscompleted.
INTER CABIN CONTROL
02.06.2020 239S1 Basics of Indian Railway Signalling Ver.1.0

239. Types of Controls Slots
1. The following types of Controls/Slots are in
general use in mechanical installations:
(a)The mechanical lever lock worked by key
transmitted electrically
(b)The electric lever lock
(c)The electric signal reverser post type
2. The design, construction and maintenance of
the various types of slots are dealt with
elsewhere.
02.06.2020 240S1 Basics of Indian Railway Signalling Ver.1.0

240. 02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
INTER CABIN CONTROL
241

241. IRISET 242MSDAC –Comparative Study Ver 1.0

242. CHAPTER -17
LOCATION OF SIGNALS
SUBJECT IRISET-SECUNDERABAD 243

243. Placement of Distant Signal
•Distant Signal shall be placed at an *adequate
distance in rear of the first Stop Signal.
•*Note: Such an adequate distance shall not be less
than 1 kilometre in Single Distant Territory
•In Double Distant territories: On sections, where
Emergency Braking Distance (EBD) of more than 1.0
km is to be catered for, a second Distant signal shall
be provided. Such a Distant signal shall be placed at
an adequate distance of not less than 2 kmsin rear
of First Stop signal and Inner Distant Signal shall be
placed at a distance of not less than 1 km in rear of
First Stop signal.
SUBJECT IRISET-SECUNDERABAD 244

244. Placement of Stop Signals
•Home Signal: The Home Signal shall be placed in rear of all
connections, if any, on the line to which it refers.
•The Home Signal shall be placed at not less than *180
metres in rear of the points up to which the line may be
obstructed, after line clear has been granted to the station
in rear.
•Starter Signal: When one Starter Signal is provided for each
converging line, it shall be so placed as to protect the
adjacent running line or lines.
SUBJECT IRISET-SECUNDERABAD 245

245. •Intermediate Starter Signal: An Intermediate Starter
Signal shall be placed clear of fouling marks in rear of
the points, if any, which it protects.
•Advanced starter -It shall be located at a distance of
not less than 120 meters from the outermost points
in the case of Single Line section. This distance shall
be reckoned from the starter in case of Double Line
Section.
SUBJECT IRISET-SECUNDERABAD 246

246. •Gate Stop Signal: shall be located at not less than
180 meter (in MACLS territory) in rear of the gate,
which it is protecting. Gate Signal shall be provided
with a marker consisting of a yellow coloured disc
with letter 'G’ in black.
SUBJECT IRISET-SECUNDERABAD 247

247. DESIGNATION AND LOCATION SIGNALS
on Single line
24802.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

248. MACLS
180 + 120

249. 250
DESIGNATION AND LOCATION SIGNALS
on Double Line
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

250.  DOUBLE DISTANT TERRITORY
Normal aspect of distant signal is attention
Post of distant signal is of is painted alternate yellow & black strip
Distant signal Placed at distance of 1 Km in rear of existing distant
Goods warning board is not required.
Station B
P
FSS of Stn B
LSS of Stn B
P
Distant. Inner Distant.
1KM
1KM

251. P
FSS
LSS
Distant.
1Km
GWB
1.4Km
SINGLE DISTANT SIGNAL TERRITORY

252. • Aspects-Sequence Chart
•Aspect sequence chart of various signals shown on
SIP as per movement of train .
•For each directional ( up /Dn) signals aspect
sequence chart provided
•When a Signal is displaying the 'Stop' aspect, the
signal next in rear shall not display a less restrictive
aspect than 'Caution'.
SUBJECT IRISET-SECUNDERABAD 253

253. SUBJECT IRISET-SECUNDERABAD 254
Distant
signal
Home signal
Main Line
Starter
Loop Line
Starter
Advanced
Starter
Indication to Loco
Pilot
Yellow Red - - -
StopdeadatHome
Double
Yellow
Yellow Red - -
StopdeadatMain
lineStarter
Green Green Green - GreenRunthroughon
MainLine
Double
yellow
Yellow with
Route
indicator
- Red -
Stopdeadatloop
linestarter
Double
Yellow
Yellow with
Route
indicator
- Yellow Green
Runthroughvia
loopline
ASPECT SEQUENCE CHART

254. SUBJECT IRISET-SECUNDERABAD 255
S.No.
Distant
signal
Inner
Distant
signal
Home
signal
Main
Line
Starter
Loop Line
Starter
Advance
d Starter
Indication to
Loco Pilot
1.
Double
Yellow
YellowRed - - -
Stopdeadat
Home
2.Green
Double
Yellow
YellowRed - -
Stopdeadat
MainlineStarter
3.
GreenGreenGreenGreen - GreenRunthroughon
MainLine
4.
Double
Yellow
Double
yellow
Yellow
with Route
indicator
- Red -
Stopdeadat
looplinestarter
5.
Double
Yellow
Double
Yellow
Yellow
with Route
indicator
- YellowGreen
Runthroughvia
loopline
ASPECT SEQUENCE CHART ( DOUBLE DISTANT SIG )

255. IRISET 256MSDAC –Comparative Study Ver 1.0

256. CHAPTER -18
LEVEL CROSSING GATES
SUBJECT IRISET-SECUNDERABAD 257

257. 25802.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
Level Crossings

258. LEVEL CROSSING GATES

259. Level crossing Gate
SUBJECT IRISET-SECUNDERABAD 260

260. What and Why
261
Whenroadtrafficcrossestherailtrafficatthesame
level,theyareknownaslevelcrossings.
Atlevelcrossings,theroadisbroughtuptothelevelof
railtableandguardrailsareprovidedtoensure
clearanceforwheelflanges.
LCsbecomenecessarybecausethealternativeof
over/underbridgesisveryexpensive
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

261. 262
Alevelcrossingwillhaveanarrangementtostop
roadtrafficoneithersideoftheX-ing(exceptatD
classX-ings).
Thisarrangementcanbeswinggates,liftingbarriers
orevenachainacrosstheroad.
Itwillhavecheckrailstokeeptheflange-wayclear.
ProvisionofWarningsignsaremandatoryoneither
sideoftheLCforwarningroadusers
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

262. Norms for deciding Class of a LC
263
Classificationisdoneconsideringclassofroad,
visibilityandvolumeofroadandrailtraffic
Numberoftrainsper24hrs.multipliedbynumberof
roadvehiclesper24hrs.givestheTrainVehicleUnits
fortheLC.
CategoryI,TVUsmorethan3000,CategoryII,less
than800mvisibilitytoroadusersandTVUmorethan
2500manningshouldbedone.
TVUsover20,000Qualifiesforinterlocking.
MinTVUsshouldbe1lakhtobecomeeligiblefor
ROB/RUBoncostsharingbasis.
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

263. LC Gates are classification depends on
•Depends on nature of road
•The no. of road vehicles passing
•The no. of trains passing.
02.06.2020 264S1 Basics of Indian Railway Signalling Ver.1.0

264. LC Gates are classified
1.SPL –Class -More than 50,000 (TVU)
2. ‘A’-Class –More than 30,000 (TVU)
3. ‘B-1’ –Class –More than 25000 (at least 750
buses/day) [TVU]
4. ‘B-2’-Class-More than 20000 (TVU)
5. ‘C’ –Class –All there road user
6. ‘D’ –Class –For cattle crossing.
“Sensor will be taken once in three year, 7 days
consecutive, on an average”.
02.06.2020 265S1 Basics of Indian Railway Signalling Ver.1.0

265. 1.TVU-Train Vehicle Unit (train unit x vehicle unit)
2.Train, Motor vehicle, bullock carts & tongues –1 unit
3.Cycle rickshaw & auto rickshaw –½ unit
4.Visibility of manned gate –5M.
5.Fencing parallel to the track –15M
6.Gate lodge –6M from center of track
7.Speed Breakers –20M from center of track
8.Height gauge –8M from center of track
9.Gate post –3M from center of track
10.TVU is more than 6000 or L.C.Gatevisibility is poor –Un manned
gate is converted into Manned gate.
Additional information For L.C.Gates
02.06.2020 266S1 Basics of Indian Railway Signalling Ver.1.0

266. Classes of level crossings
267
•Special class: TVUs > 50,000
•A’ class : TVUs > 30,000 and <50,000
•B1 class : TVUs > 25,000 and <30,000
•B2 class : TVUs > 20,000 and <25,000
•C’ class (Md) : Category I > 3000 Cat II > 2500
•D’ class : Cattle crossing
(TVU’s > 20,000 Shall be Normally kept open to Road Traffic
C’ class if interlocked, shall be normally kept open to RT)
If average number of trains is less “say up to 14 in a day”, the
normal position can be changed to “Open to road traffic”
regards less of TVU’s
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

267. Sl.
No.
DETAILS
CLASSES
Other
Stipulations
Special
Class
> 50,000
‘A’
> 30,000
< 50,000
‘B1’
> 25,000
< 30,000
‘B2’
> 20,000
< 25,000
‘C’
Cat I > 3000
Cat II > 2500
1Interlocking Gates with Signals
a
If within station
limit
Should be interlocked with station signals
Should be
interlocked with
station signals
b
If outside the
station limit
Should be interlocked with gate signals
Should be
interlocked with
gate signals
Sub Urban &
Auto section all
to be
interlocked
cNormal positionOpen to road traffic
Open to road
traffic if
Inter Locked
2Telephone Communicated from the Gate lodge
a
Within or
outside station
limit
Telephone to be provided with the ASM's office with all the
manned LC Gates
02.06.2020 268S1 Basics of Indian Railway Signalling Ver.1.0
Classes of level crossings

268. Sl.
No.
DETAILS
CLASSES
Other
Stipulations
Special
Class
> 50,000
‘A’
> 30,000
< 50,000
‘B1’
> 25,000
< 30,000
‘B2’
> 20,000
< 25,000
‘C’
Cat I > 3000
Cat II > 2500
3Warning bell or Hooters operated by App Trains
a
Within or
outside station
limit
Should be provided
Should be
provided
4Type of Lifting Barrier
a
Within or
outside station
limit
Electrically Operated Lifting BarrierEOLB in SU
5Approach Locking
a
To be provided in Sub Urban section
Others -DA Locking -30 sec
To be provided
in SU
Others -DAL-30
sec for EOLB
02.06.2020 269S1 Basics of Indian Railway Signalling Ver.1.0
Classes of level crossings

269. Gate Signals
270
AGateStopSignalshallbefixedatanadequatedistance
fromthegate.
TheGateStopSignalshallbeprovidedwith‘G’marker
exceptwhereprohibitedunderspecialinstructions
Multipleaspect/modifiedlowerquadrantsignalling,aStop
Signalat180metresfromthegateandaDistantsignalat1
kminrearoftheStopSignalmaybeprovided.
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

270. 271
OnsectionsprovidedwithMultipleaspectsignalling,
whentheinterlockedgatesaresituatedbetween
DistantandHomesignal-
(a)TheGateSignalshallbelocatedat180metresinrear
ofthegate;
(b)TheDistantSignalshallbelocatedatnotlessthan1
kminrearoftheGateSignalandwillfunctionas
GateDistantaswell.
Interlocked Gates within Station Limits
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

271. Gate Stop
Signal
Gate Stop Signal in
Automatic Block Territory
(Letter A shall be lit only
when gates are closed
and locked against road
traffic)
Refer GR 3.17
A AG
Gate Stop Signal in semi-
automatic territory
(Letter A shall be lit only
when gates are closed
and locked & points are
correctly set and locked.
Letter AG shall be lit
when points are
correctly set and locked
but gate is open or
defective.)
G GA
27202.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

272. Level crossing located within station
limits in MA signalling
273P
(3) (2) (1)
S.O
120M1KM.B.D
B.O
180M
UP STARTERS
STARTER
UP.ADV.
UP DN
DN.DISTANT
BOARD
1.4 KM
DN.HOME
GOODS WARNING
The gate shall be interlocked with down Homes,
up starter, and up Homes
18.11.2020 S1 Basics of Indian Railway Signalling Ver.1.1

273. Level crossing located within station
limits in Double Line MACLS
274BSLB
180M
1.4 KM
P
1KM
ThegateshallbeinterlockedwithdownHomes,upstarter,
andupHomes
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

274. L.C gate is between the down Homes
and up advance starter
275P
180M
1KM 180M
P
1KM
1.4 KM
The gate should be interlocked with down Homes and up
advance starter only
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

275. 276P
(i)
STARTER
UP.ADV.
HOMES
ROUTING
HOMEDISTANT
1KM
1.4 KM
180M P
180M
1KM
L.C gate is little away from the down Homes, The gate interlocked with down
Home signal and the up advanced starter and with routing homes if required.
If the gate is just in rear of the Homes the Home may be shifted at 180m in rear of
the gate
L.C gate is between the down Home
and Down Distant
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0

276. 277
Sr. Distant Gate cum
Distance
Home Remarks
1YELLOW RED ----- Stop at Gate Signal
2GREEN YELLOW RED Stop at Home Signal
3GREEN DOUBLE
YELLOW
YELLOW / YELLOW
WITH ROUTE
Going to be received on
main line / loop line
4GREEN GREEN GREEN Train is on run through via
main line
18.11.2020 S1 Basics of Indian Railway Signalling Ver.1.1

277. IRISET 278MSDAC –Comparative Study Ver 1.0

278. CHAPTER-19
SECTION CAPACITY
SUBJECT IRISET-SECUNDERABAD 279

279. Section Capacity
•Themaximumnumberoftrainsthatcanbedealton
agivensectionofRailwayduringtheperiodof24
hours,iscalledtheSectionCapacity.
•Itisexpressedasnumberoftrainseachwayon
singleline
02.06.2020 280S1 Basics of Indian Railway Signalling Ver.1.0

280. Scott’s FORMULLA:
• 24 x 60
C = ------------x E x 1/2
T + t
Where, C = Section Capacity
T = Running Time of slowest train to pass Ruling Block
Section
t = Average Time required for Sginalling and Block
operations
E = Efficiency factor (80)
Section Capacity
02.06.2020 281S1 Basics of Indian Railway Signalling Ver.1.0

281. Section Capacity
18.11.2020 282S1 Basics of Indian Railway Signalling Ver.1.1
Tp = Running time of Passenger train
Tg = Running time of Goods train
Cg = Section capacity of Goods train

282. •Onsinglelinesectionthelinecapacitycanbe
augmentedbyimproving`T'and`t'ofScott'sformula,
aswellasthe`E'factor,Tcanbereducedby
Section Capacity
02.06.2020 283S1 Basics of Indian Railway Signalling Ver.1.0

283. –Reducing the length of block section by providing additional
crossing stations.
–Increasing speed by providing better mode of traction, tracks,
rolling stocks and signalling.
`t' may be reduced by introducing
oHigher standard of interlocking
oToken less block instruments
oPanel interlocking
oCTC and Automatic signalling
Section Capacity
02.06.2020 284S1 Basics of Indian Railway Signalling Ver.1.0

284. Section Capacity
•`E'(Efficiencyfactor)canbeimprovedbypropertime
tabling,punctuality,staffefficiency,upkeepof
equipments,
•Efficientoperation,adequatenumberoflooplines,
suitablelengthofblocksectionandIBSondouble
line,etc.
•Simplificationofrules,trainingofstaffisalsothe
factorstoimprovetheoperatingefficiency.
02.06.2020 285S1 Basics of Indian Railway Signalling Ver.1.0

285. IRISET 286MSDAC –Comparative Study Ver 1.0

286. CHAPTER -20
Principles of Signal Engineering
SUBJECT IRISET-SECUNDERABAD 287

287. Principles of Signal Engineering
•Failsafefeature
•NormalDangersystem
•ZeroSightingDistance
•Oneaspectoneindication
•Visibilityfromtheplaceofoperation
•Overlaps
•Operationfriendly
•RAMS
•Uniformityofsignals
•ContinuousvisibilitytoDriver
•IndependentBlock&Yardsignaling
•Minimumsignalsonaroute
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0 288

288. Fail Safe Design
•Safetyofpassengersandefficiencyofoperationbeing
thetwinpurposesforwhichfixedsignalsareinstalled.
•Eachandeveryapparatusandcircuitemployedina
signallingsystemshallbesodesignedthatafailure
occurringinanyofthecomponentpartsofthesystem
resultsinthesignalorsignalscontrolledbythesystem
displayingtheirmostrestrictiveaspects.
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0 289

289. RAMS
•Reliability,Availability,MaintainabilityandSafetyshallbe
importantconsiderationinthedesignofapparatus,circuits
andsystems
•Theaspectsoffixedsignalsshallbedistinctiveand
unambiguous
•Oneaspectshallhavebutonenameandoneindication,
converselyforagivenindicationthesameaspectshallbe
usedeverywhereandatalltimes.
18.11.2020 S1 Basics of Indian Railway Signalling Ver.1.1 290

290. •Theactionrequiredbyasignalindicationshallbedefinite
andcapableofeasyimplementation.
•Eachandeverysignalshallaffordthesightingdistance
required,ofit.
•Thenumberoffixedsignalsprovidedshallbetheminimum
foreachroute.
•Theoverlapsrequiredforeachsystemofaspectsshallbe
clearlyspecified.
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0 291
RAMS

291. Essentials of Interlocking
EssentialsofInterlocking:Equipmentsprovidedforthe
operationandcontrolofsignals,points,etc.,shallbeso
interlockedandarrangedastocomplywiththefollowing
essentials;
(a)Itshallnotbepossibletotake'OFF'aMainstopsignal
oraSubsidiarysignal,unlessallpointsintheroute,
includingoverlapandisolation(asapplicable),are
correctlysetandlockedandallinterlockedlevelcrossing
areclosedandlockedagainstpublicroad,andrelevant
tracksareunoccupiedbyvehiclesandclearfortheline
onwhichthetrainwilltravel.
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0 292

292. Essentials of Interlocking
(b)Aftersuchsignalhasbeentaken„OFF‟,itshallneither
bepossibletomoveanypointsnorunlocktheroute,
includingoverlapandisolation,nortoopenany
interlockedgatesuntiltheconcernedsignalis
replacedto'ON'position.
(c)Itshallnotbepossibletotake'OFF'anytwosignals
simultaneously,whichcanleadtoconflicting
movements.7.6.2RouteHolding(ApproachLocking
&BackLocking
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0 293