.~ Detached locking, check locking, or key control
DEFINITION
Classification: 246/159
(under subclass 131) Subject matter having mechanism spatially separated from but interlocked with the mechanism of the central tower and usually located near switches and signals, whereby they can be shifted by others than the tower operator, provided the conditions are safe for such movement, in which case the full protection of the entire interlocking system is afforded until the switches and signals are properly replaced.
(1) Note. This subclass includes the so-called "Annette's key" and similar movable devices and also what is known as "check-locking", whereby the levers in two adjacent interlocking plants are so interlocked temporarily as to permit train movements between them to be made safely against the current of traffic.
SEE OR SEARCH THIS CLASS, SUBCLASS:
19, for staff and tablet block systems.
131, and appropriate indented subclasses.
160, for systems having means to lock the switch or signal in position upon the approach of a train.
