Page 494 - IRSEM_Main Book

(c) The route release circuit shall be so designed that it will release only
when at least two track circuits drop and pick-up in sequence.
(d) In installations provided with route setting system, sectional route release
shall be provided if number of routes are more than 100. In such cases
sub-route section already released shall permit setting up of other routes,
if interlocking otherwise permits.

(e) In case of installations provided with non-route setting system, sectional
route release shall be provided if number of routes are more than 100.
The complete route release shall be effective only after the signal
governing the route is put back to 'ON' and corresponding route
switch/push button has been operated to normalize the route. However,
where sequence proving relays are provided to prove the authorized
passage of a train, automatic route release shall be provided.

(f) It shall be possible to release a route in emergency after suitable time
delay as per Table-1, with the approach track occupied, provided the
train has not passed the signal during the time interval.

(g) It shall be possible to release a route in emergency after a suitable time
delay as per Table-1 at para 21.1.21, where approach track circuits have
not been provided and after the signal has been put back to danger
provided the train has not passed the signal during this time interval.

(h) When the route is released by the passage of train, the overlap points shall
be released only after the lapse of suitable time delay as per Table-1 at para
21.1.21 after clearance of last point track circuit of the route i.e. the train is on
berthing track. (However, in major yard this timing of route release can be
reduced as per Table-1 with the approval of PCSTE). On cancellation, the
overlap points shall be released simultaneously along with the main route.

(i) Facility of emergency route/sub-route cancellation shall be provided and
it shall be possible to release the route/sub-route with suitable time delay
as per Table-1 at para 21.1.21. Cancellation shall be operated after
physical verification of the line by traffic representative. Every such
cancellation shall be recorded on a non-resettable counter and in a
register to be maintained by traffic representative.

21.1.9 Signal Control Circuits

(a) It shall not be possible for a signal to assume 'OFF' aspect in installations
provided with route setting facility unless the route switches/buttons have
been operated and relevant route has been correctly set and locked and
relevant track circuits are clear. In installation provided with non-route
setting facility, the signal shall not assume 'OFF' aspect unless the route
is set and locked, relevant track circuits are clear and signal
switch/button has been operated. In case self-restoring type of push
buttons are used, signal shall not assume 'OFF' aspect unless concerned
push buttons are pressed simultaneously for 3 seconds and released.

(b) Circuits shall be so designed that the failure of any part of a circuit
affecting the control of the signal shall cause the signal to display a most
restrictive aspect.

Chapter 21: Relay & Electronic Interlocking Page 440 of 535