Page 476 - IRSEM_Main Book

20.1.4 Establishing Direction of Traffic for Automatic Stop Signals on Single Line

(a) A Control shall be provided to establish direction of traffic and to ensure that
conflicting signals can not be taken off and a suitable indicator provided to
indicate the direction established. It shall not be possible to change the
direction unless the entire line between two crossing stations and the overlap
in the direction to be established are Clear. The mechanism of the control
shall, in addition, be suitably approach locked.

(b) Automatic Stop Signals shall operate in the direction of traffic established.
Those Automatic Stop Signals which are against the direction of traffic must
exhibit 'ON' position.

20.1.5 Train Detection (Track Circuits/Axle Counter) for Automatic Signalling

(a) The line shall be provided with track circuits or Axle Counters over its entire
length and may be divided into a series of Automatic Signalling Track Sections.
The Track Circuit for the overlap must be separated from the Track Circuits
for the remaining portion of each signalling section. In case of Axle Counters,
track section may be extended from foot of the next signal in advance up to
an adequate distance beyond it.

(b) DC Track circuits are not to be provided in block section, in future working
due to maintenance issues.

(c) Track circuits/Axle Counter shall also be provided on all passenger running
lines as well as other reception lines between passenger lines including their
connections to the main lines at all stations on the Automatic Section including
stations at either end of the section. There shall be no dead section between
the Track Circuits/Track sections of the station and the Track Circuits/Track
sections of the Automatic Section.

(d) The design of the Axle Counters between two adjacent stations, shall be such
that, individual track sections in each direction shall have resetting facility
from dispatching end station master in case of failure of equipment, with co-
operation of receiving end station master for verification of last vehicle.

(e) Redundancy may be provided in Track circuits/Axle Counters in the Automatic
Section to improve availability.

(f) Media diversity shall preferably be provided for Axle Counters.

(g) Track indicator for Automatic Signalling on Single Line: An indicator shall be
provided at each station to indicate whether the block section is occupied or
clear.

20.1.6 Markers

(a) 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.

(b) 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.

Chapter 20: Automatic Block Signalling Page 422 of 535