INTRODUCTION TO SIGNALLING

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INTRODUCTION TO SIGNALLING Station
signaling- Consists of
Signals,
Points,
Track circuits Purpose
1. For safe running of Trains i.e.,
to ensure safe running of
trains. 2. To facilitate to
deal no. of trains
by providing crossing precedence.
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• For a train to come into station, stop at
  station and start from station requires some
  demarcation which is a signal. Basically for
  safe control of train movements a signal is
  required in the station section.
• If no signal is available for the driver he will
  not be knowing where he has to control the train
  and may collide with other train which is already
  stopped or the train coming in the opposite
  direction.
• Controlling the train movements in a station
  manually is unsafe, time consuming and dealing
  number of trains at a time is not possible.

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• Points are meant for diverge a train from one
  line to other line thereby dealing number of
  trains in a station depend upon number of lines.
  Hence points are required in a station.
• If no points are there in a station one train can
  only be dealt at a time. This directly affects
  the density of train traffic.
• The maintenance of the points is so important
  that any gap gt5mm in between Stock rail and
  switch rail causes derailment of train.

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• Track circuits are required in a station for
• If no track circuits are there in a station,
  signal can be taken off even when there is a
  train in the station.
• Track circuit parameters vary as per the weather
  conditions. The adjustment shall so carefully
  done and observed that the track circuit shall
  not be clear when it is in occupied condition.
• If the track circuit is provided on the point
  Zone it locks the point and avoid the operation
  of point during the train movement over it.
  Otherwise the train gets derailed. Any mal
  adjustment of track circuit causes operation of
  point during train movement.

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• b) Block signaling
• Consists of Two block instruments for one
  section (between two
  stations) which are
  interlocked.
• Purpose 1. Ensures safe running of
  trains between two stations.
• 2. To increase section capacity.

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• Block instruments are required to control
  in/out movement of trains between two station.
• If no Block instruments are provided the train
  movement have to be controlled manually in which
  human error may cause sending of two trains in
  one block section.
• By providing block instruments one train only can
  be sent in to block section.

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• Developments in station signaling.
• Mechanical Signaling
• Key locked operation
• Single wire operation
• Double wire operation
• Rod operation.
• Electrical Signaling
• Colour light signaling Electromechanical
• Colour light signaling with Panel Interlocking
• Electronic Interlocking (SSI)

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• Developments in Block Signaling
• One train only system
• Absolute Block system
• Token Block instruments.
• Token less Block Signaling
• Block Proving Axle counters
• Automatic Block signaling system.