Door alarm system responsive to forced entry

摘要

Alarm system in which the latch plate of the door jamb is movable to contact a striker plate spaced and insulated therefrom to close an alarm circuit. The system is so designed that if an attempt is made to force the lock, the latch plate which is resiliently mounted will move and thus make contact with the striker plate. A contact relay and thermal relay are incorporated in the alarm system in such a way that the alarm can be timed to signal for a predetermined length of time after which it will automatically shut off. As soon as the alarm signal has stopped the system is ready to signal again.