Anti-theft alarm system for dwelling or vehicle - is responsive to current variation and includes storage capacitor

摘要

The anti-theft device for protecting a dwelling or a parked vehicle has a conductor (4) associated with an access door or window, the current variation in the conductor (4) caused by opening and triggering an alarm. In order to trigger the alarm when the current circuit is interrupted, a charge storage capacitor (13) is connected in parallel with it. The current circuit and the parallel capacitor (13) are pref. coupled to the current source, eg the vehicle battery (1), via a protective resistance. A transistor (11, 12) may be connected in series with the capacitor, which only becomes conductive when the current circuit is interrupted.