Page 180 - IRSEM_Main Book

(c) Stop Signals which are next in advance of trailing points operated from
the same cabin, when taken off, lock such point in either position unless
route locking is provided or the distance between the Points and the
signal is such that the locking interferes with traffic movement.

7.6.4 Train Detection - Track Circuiting/Axle Counters

(a) Where continuous track circuiting/Axle Counters are provided, the
occupation by a vehicle of any track circuited/Axle Counter section shall
control the signals leading to the same line and shall also lock the Points
on the route.

(b) At stations where points and signals are operated through Relay
Interlocking/Electronic Interlocking, track circuiting/Axle Counters shall be
provided, for entire station section for all lines, where direct reception is
provided.

(c) In case of Cabins with mechanically operated signals & points, all
passenger lines or where light engine crossing and shunt movements are
frequent or where stop Signals are at a considerable distance from the
Cabin, or where the view of the Operator is likely to be obstructed, the
provision of track circuits or Axle Counters is essential.

7.6.5 Clearance at Junction Point

(a) Where it is difficult under normal conditions of visibility for an Operator to
estimate clearance, track circuiting/Axle counter shall be provided in
order to define the *fouling points of junctions, loops, siding connections,
crossings etc.

(b) Where the movement of trains over the Points is not visible to the
Operator operating the Points - Occupation of the track between Stop
Signal reading over the Points up to the fouling mark ahead of such
Points shall be electrically indicated at the place of operation.

Note (i) *Fouling means the marks at which the infringement of two fixed Standard
Dimensions fouling block occurs, where two lines cross or join one another. (GR).

It shall be placed at a location, where centre to centre distance is less than 4265 mm
for existing works and 5300 mm for new works/Alteration to existing works.
(Reference: SOD for BG Track – Chapter-II-item-1).
(ii) Whenever the term Track circuit is used, it shall automatically cover the use of
axle counter or any other approved means of train detection.

7.6.6 Slot controls on signals

(a) Where a signal is controlled through slots, it shall not be possible to take
'off' a signal unless all the controls have been exercised by the
controlling agencies. But it shall be possible for any one of the controlling
agencies to replace the signal to 'ON' position by withdrawal of the
control.

(b) Slot circuits shall be so designed, that a slot once given is effective for
only one train and a fresh slot has to be given for a subsequent train.

Chapter 7: Essentials of Signalling Page 149 of 535