Page 475 - IRSEM_Main Book

(b) Semi-Automatic Stop Signals: A fixed signal having both manual and track
circuit controls and which is capable of being operated either as an Automatic
Stop Signal or a Manual Stop Signal, is called a Semi-Automatic Stop Signal
i.e they are capable of being operated either as Automatic Stop Signals or
as Manual Stop Signals as per need.

(i) The Semi-Automatic Stop Signal when working as an Automatic Stop
Signal shall conform to an Automatic Stop Signal in all matters relegating
to its functioning including its normal aspect.

(ii) Similarly, a Semi-Automatic Stop Signal when working as a Manual Stop
Signal shall conform to Manual Stop Signals in all matters including its
normal aspect.

A control may be provided to make a Semi-Automatic Stop Signal to work
either as an Automatic Stop Signal or as a Manual Stop Signal as required.

20.1.3 Special Requirements of Automatic Block System on Single Line

In case of single line, Line clear shall be obtained and Direction of Traffic shall
be established as per GR 9.03 (Extract given below)

GR 9.03. Essentials of the Automatic Block System on single line.

(1) Where trains on a single line are worked on the Automatic Block System,
(a) The line shall be provided with continuous track circuiting or axle counters,

(b) The direction of traffic shall be established only after Line Clear has been
obtained from the block station in advance,
(c) A train shall be started from one block station to another only after the
direction of traffic has been established,

(d) It shall not be possible to obtain Line Clear unless the line is clear, at the
block station from which Line Clear is obtained, not only up to the first Stop
signal but also for an adequate distance beyond it,
(e) The line between two adjacent block stations may, where required, be
divided into two or more automatic block signaling sections by provision of
Stop signals,

(f) After the direction of traffic has been established, movement of trains into,
through and out of each automatic block signaling section shall be controlled
by the concerned Automatic Stop signal and the said Automatic Stop signal
shall not assume ‘off’ position unless the line is clear up to the next
Automatic Stop signal:

Provided further that where the next Stop signal is a Manual Stop signal,
the line is clear for an adequate distance beyond it, and

(g) All Stop signals against the direction of traffic shall be at ‘on’.

(2) Unless otherwise directed by approved special instructions, the adequate distance
referred to in clauses (d) and (f) of sub-rule (1) shall not be less than 180 meters.

Chapter 20: Automatic Block Signalling Page 421 of 535