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assemblies Importance of Loco TCAS modes and their transitions Learning about Loco Pilot actions under different scenarios

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TypeCommercial Circular
Topicreservation
CurrencyCurrency not verified

Summary

assemblies Importance of Loco TCAS modes and their transitions Learning about Loco Pilot actions under different scenarios The Loco TCAS unit shall switch to the System Failure mode in case of

Text of the circular

Train Collision Avoidance System (TCAS) 
Loco TCAS 
Basics Overview

Objectives
To understand the basic working principle of Automatic Train Protection 
acheived through TCAS system
Knowing major components of TCAS system
Knowing Loco TCAS sub-assemblies
Importance of Loco TCAS modes and their transitions
Learning about Loco Pilot actions under different scenarios

Background
Disregard  of  Railway  Signal  by  Loco Pilot can  lead  to potential  hazards
Signal  Passing At Danger (SPAD)  is  safety  concern  for  Indian  
Railways
Train    Collision    Avoidance    System  (TCAS),    an    indigenous    Automatic   
Train  Protection (ATP)  system  to  prevent  accidents  caused due to 
SPAD, 
Loss of Speed Supervision, and 
Train Collisions
by automatic  application  of  brakes  in  case of Loco  Pilot fails  to  do  so 
Inherent feature of Cab Signalling is useful during normal running as well as in 
foggy weather
TCAS system is designed to meet the safe operation of trains.

TCAS System 
BRAKE
INTERFACE UNIT
ONBOARD
COMPUTER
LP
OCIP
SIGNAL
ASPECT RELAYS
STATION
TCS
CONTROL
UNIT
SIM
OCP
Track occupancy status
Point/Switch status
STATION
RF ANTENNA
RFID TAG READER
RFID TAGS
GPS & GSM
ANTENNA
RF, GPS & GSM
ANTENNA

TCAS System 
SIGNAL
ASPECT RELAYS
STATION
TCS
CONTROL
UNIT
SIM
OCP
Track occupancy status
Point/Switch status
STATION
RF ANTENNA
RFID TAGS
GPS & GSM
ANTENNA
BRAKE
INTERFACE UNIT
ONBOARD
COMPUTER
LP
OCIP
RF, GPS & GSM
ANTENNA
Stationary TCAS in 
listening mode
Location
Track Identification No
Direction - undefined

TCAS System 
SIGNAL
ASPECT RELAYS
STATION
TCS
CONTROL
UNIT
SIM
OCP
Track occupancy status
Point/Switch status
STATION
RF ANTENNA
RFID TAG READER
RFID TAGS
GPS & GSM
ANTENNA
BRAKE
INTERFACE UNIT
ONBOARD
COMPUTER
LP
OCIP
RF, GPS & GSM
ANTENNA
Location
Track Identification No
Direction - Normal/ reverse
Speed
Train Length
Stationary TCAS registers the loco TCAS
Secured communication establishes 
between  Loco and Stationary TCAS

TCAS System 
SIGNAL
ASPECT RELAYS
STATION
TCS
CONTROL
UNIT
SIM
OCP
Track occupancy status
Point/Switch status
STATION
RF ANTENNA
RFID TAGS
GPS & GSM
ANTENNA
BRAKE
INTERFACE UNIT
ONBOARD
COMPUTER
LP
OCIP
RF, GPS & GSM
ANTENNA
Stationary TCAS sends:
Static Section Profile
Movement Authority
Signal informattion
wrt to Loco TCAS location
(every 2 sec)
Location
Track Identification No
Direction - Normal/ reverse
Speed
Train Length
(every 2 sec)

TCAS System 
SIGNAL
ASPECT RELAYS
STATION
TCS
CONTROL
UNIT
SIM
OCP
Track occupancy status
Point/Switch status
STATION
RF ANTENNA
RFID TAGS
GPS & GSM
ANTENNA
BRAKE
INTERFACE UNIT
ONBOARD
COMPUTER
LP
OCIP
Loco TCAS tries to attain 
zero speed before the 
stop signal (danger)
to prevent SPAD

TCAS – General Functionality

TCAS Features – Speed Supervision
Static speed profile
The Static Speed Profile (SSP) is a description of the fixed 
speed restrictions for a part of track sent from track side to 
train
Speed Supervision
Loop Line Speed
Section/ Line Speed
Max Train Speed
Permanent Speed Restrictions (PSR)
Speed related to loco modes
Remote Introduction of Temporary Speed Restrictions (TSR)

TCAS Features - MA
Movement Authority
The distance upto which 
the train is permitted to 
travel safely
End  of  Authority  (EOA)
Location  up  to  which  
the  train  is  permitted  to 
proceed and where 
target speed should be 
zero

TCAS Safety Features
Prevention of signal passing at danger (SPAD)
Cab Singnaling, loop line speed control
Prevention of over-speed: section speed, train speed, PSR
Protection of roll back and reverse movements
Prevention of side-collision in block section
Prevention of head-on and rear end collisions
LC gate automatic warning
SoS messages
Computation of train length
Shunt limits validation
Centralized live monitoring of train movements in NMS

Radio 
Unit
Station Antenna
SOIP
Relay Rack
STCAS
Station TCAS Equipment

•
RFID Tags provided in block
section at ~1 km and in stati

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