Page 477 - IRSEM_Main Book

(c) Such a Signal interlocked with a level-crossing shall be provided with a 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.

(d) 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.

(i) Such a 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.

(ii) When a Semi-Automatic Stop signal is required to protect a level crossing
gate as also points, the signal may be provided with an illuminated 'AG'
marker in addition to the illuminated 'A' marker.

(e) The illuminated markers of a Semi-Automatic Stop Signal shall preferably be
repeated at the place of operation of the Signal along with the aspects of the
Signal.

20.1.7 Restrictions in Graded Sections

(a) Automatic Signalling shall not be provided on sections with heavy and
continuous falling gradients steeper than 1 in 80 unless the brake power of
trains on the section is adequate to enable the trains being stopped at each
of the Automatic Stop Signal.

(b) The suitability of Automatic Signalling on heavy and continuous rising
gradients shall be decided in consultation with the concerned Departments
duly taking into account the ability of a train to start after it has been stopped
at an Automatic Stop Signal.

(c) Points and Crossings in Automatic Block Sections: Emergency Crossovers
and Siding Points shall be secured and approach locked and detected by
Signals reading over the Points.

Section 2: Installation of Automatic Signalling

20.2.1 The installation and wiring shall be carried out as per approved plan and Circuit
Diagrams.

The circuits and equipment shall be so installed as to cause minimum failures
while ensuring maximum safety.

20.2.2 Circuit Features for Auto Signals

(a) The aspects of an automatic signal shall be controlled by the main signal in
advance through lamp proving relays/object controller, in addition to the
controlling relays.

(b) All fail-safe circuits shall work on continuously energized principle such that
any open circuit in wiring, relay contacts, etc. or loss of power supplies shall
not cause an unsafe condition.

Chapter 20: Automatic Block Signalling Page 423 of 535