Page 168 - IRSEM_Main Book

(e) Advanced Starter Signal: Unless approved under special instructions, an
Advanced Starter Signal shall be placed outside all connections on the
line to which it applies;

It shall be located at a distance of not less than 120 meters from the
outermost points in the case of Single Line section. This distance shall be
reckoned from the starter in case of Double Line Section.

(f) Gate Stop Signal: shall be located at not less than 180 meter (in MACLS
territory) in rear of the gate, which it is protecting. Gate Signal shall be
provided with a marker consisting of a yellow coloured disc with letter 'G’
in black.

(g) Intermediate Block Stop (IBS) signal: Is the Home signal provided at an
Intermediate Block post on a Double Line or Single Line. IB Signal shall be
provided with a marker consisting of a white coloured disc with letter ‘IB’ in
black.

Note: IB Signal shall be located in such a way, to split the block section into near
halves, subject to other criteria & guidelines in force.

(h) Automatic Block Signals: They shall be normally located with a spacing
of one km from each other, subject to other criteria and headway required.
Automatic Signal shall be provided with a marker consisting of a white
coloured disc with letter 'A' in black.

7.1.15 Aspects-Sequence

(a) When a Signal is displaying the 'Stop' aspect, the signal next in rear shall
not display a less restrictive aspect than 'Caution'.

(b) Every Multiple Aspect Signal, whether automatic, semi-automatic, or
manually operated which, is required to display 'caution' aspect to a train
shall normally be placed at an adequate distance from the next signal in
advance. This adequate distance shall not be less than 1 kilometre.
Where the adequate distance cannot be provided and the 'caution' aspect
is being displayed, the next signal in rear shall display the
'attention'/'caution' aspect.

(c) If necessary, the 'Attention'/'Caution' aspect shall be repeated back on
successive signals in rear, until the adequate distance is obtained.

(d) In all cases the signal next in rear of a Signal protecting diverging lines shall
display 'Attention'/'Caution' aspect in the 'OFF' position, when the points are
set for any line other than the line over which the higher speed is permitted.
When this signal cannot be placed sufficiently in rear of the 'STOP' signal
protecting the Points to permit the Loco pilot of an approaching train to
reduce to the permitted speed, the 'Attention'/'Caution' aspect shall be
repeated back on successive signals in rear, until the required adequate
distance is obtained.

Chapter 7: Essentials of Signalling Page 137 of 535