A locking arrangement with built-in alarm mechanism utilizing a contact between portions of a split bolt arrangement as the prime security measure is described. Correct sequencing of both the locking and unlocking actions is required to prevent alarm. Two realizations are described: a self-contained unit for building doors; and an automobile unit with central alarm, alarm sensors for ignition and other locations subject to tampering (hood, trunk, battery), and a set resistance method to prevent disarming by either circuit opening or shorting techniques.
An alarm device for a lock which provides a security system which displays unauthorized tampering with the lock. The device senses unauthorized movement of one or several elements in the lock and causes an alarm signal which may only be terminated by resetting the device by authorized operation of the lock.
When an ignition switch detects that a key rotor of an ignition key cylinder has been turned to the accessory position by a key, a controller energizes a primary coil to cause it to output a high-frequency signal. In the key, a secondary battery is charged with a constant DC voltage generated from an AC voltage induced across a secondary coil. A transmission circuit is powered by the secondary battery, and allowed by a timer circuit to transmit a radio signal including an identification code during a predetermined period after the high-frequency signal is received by the key. Alternatively, the controller energizes the primary coil plural times with a cycle consisting of predetermined output and pause periods if the transmitted identification code does not coincide with a preset identification code at the first comparing attempt.
