System for protecting electronic devices, particularly car radios against theft

摘要

In this system, a bistable element, which remains in a first stable state when an operating voltage is present and passes into a second state after the operating voltage has been interrupted, is connected to an operating voltage source arranged outside the device. The bistable element is connected to a microcomputer which prevents the device from being taken into operation in the case of the second stable state and places the bistable element into the first stable state after a codeword has been input.