The device uses a number of surveillance contacts associated with different parts of the protected vehicle and each coupled to an alarm signalling device via an electronic control with a number of parallel circuits. Each of the parallel circuits has a multivibrator stage and is associated an input delay stage and an alarm delay stage, the former incorporating a logic gate for only allowing the alarm release signal to be transferred when the device is in the surveillance state. The device is automatically switched into the surveillance state by an initiation stage responsive to the vehicle ignition being switched off and comprising a delayed multivibrator, providing sufficient time for the driver to leave the vehicle. The device provides secure protection without requiring effort on the part of the driver.
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