Page 313 - IRSEM_Main Book

(vi) Special/Conditional Locking

(vii) Figure 2 is an example of special locking, where 1 is released by 3
when 2 is normal. The method should be as follows:-

 Try 1, 1 should be locked,
 Pull 2 and try 1, 1 should be free,

 Pull 1, 3 should be locked and 2 backlocked.

 Replace all levers. Pull 3 and try 1, 1 should be free,

 Pull 1, 2 should be locked and 3 backlocked.

 In each case, where a lever is released by a special combination,
as in Fig.3, where 1 is released by 4 with 2 and 3 normal, each
part of the combination must be tested on the same principle as
before. Either 2 reverseor 3 reverse must "break-down" the
release on 1 by 4.

 Reciprocal Locks and Checking

 As each lock is tested, its reciprocal should, whenever possible, be
tested at the same time. As and when they are dealt with, the
figures must be ticked off on the interlocking table so that no lock
is missed.

 Locked Levers

 While testing a locked lever, a steady pressure should be applied so
as to ensure that it is not free before the releasing lever has completed
its travel. This will prove that there are no conflicting notches.

Chapter 12: Installation, Testing & Maintenance of Mechanical Signalling Equipment Page 267 of 535