Page 310 - IRSEM_Main Book

12.26.3 Essential Requirements of Locking to be Tested

(a) It is essential that the interlocking of all signals with the points is so
effected as to ensure the following conditions:-

(i) It shall not be possible to take 'OFF' a running signal until all points on the
running line are correctly set and the facing points locked, all points giving
access to the running lines from interlocked siding and goods lines are set
against the running lines and interlocked level crossing gates on the routes
including overlap are closed and locked across the road way. A signal
lever when pulled shall lock or back lock as necessary the levers operating
the points and gate locks referred to above.

(ii) It shall not be possible to take 'OFF' conflicting signals at the same time.

(iii) When signals are at 'ON', all points, which would be locked by the
taking 'OFF' of such signals, shall be free.

(iv) It shall not be possible to take 'OFF' a Warner Signal until all the
relative Stop Signals in advance have first been taken 'OFF' and when
'OFF' it must back lock such signals.

(v) It shall not be possible to take 'OFF' main home signal to proceed
aspect unless all advance signals like advanced starter, intermediate
starter and main line starter are taken 'OFF'.

(b) The locking in the frame shall correspond with that shown in the approved
Interlocking Table.

(c) The Locking shall be strong, durable and accurate and it should not be
possible –

(i) for any mechanical lock to enter a notch other than that for which it is
intended;

(ii) to force the locking.

(d) The locking in the lever frame shall act on the commencement of the
movement of the lever in the case of a direct type lever frame. In the case
of a catch handle type of lever frame, the locking shall act on the
commencement of the movement of the catch handle.

(e) The release locking shall not be effected before the completion of the
movement of lever and releasing the catch handle in the case of catch
handle type lever frame.

(f) Lever collars and slide collars shall be tested so that it is not possible to
operate a lever or slide with a collar placed on it.

12.26.4 Methods of Testing

(a) There are two methods of testing the locking:-

(i) against the Interlocking Table, and

(ii) against the signalling Plan.

Chapter 12: Installation, Testing & Maintenance of Mechanical Signalling Equipment Page 264 of 535