Time-delay combination locks

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A time-delay combination lock is a combination lock equipped with a delay timer that delays the actual unlocking of the combination lock by a preset delay, usually less than one hour. Unlike the time lock, which unlocks at a preset time and must be manually reset daily to a new time (as in the case of a bank vault), time-delay locks operate at any given time, but the operator must wait for several minutes to elapse before the lock actually unlocks.

Time-delay combination locks are usually incorporated into money safes as a robbery deterrent, since most robbers are unwilling to wait around for the timer to unlock the safe. In many instances, time-delay combination locks are also equipped with an 'ambush' combination which may be dialed that will activate the time delay as well as send a silent alarm.