Abstract: An antitheft device for a motor vehicle has a pushbutton disarming circuit coupled to a passive ignition cut-out circuit and to a passive arming circuit. The ignition cut-out circuit is interposed in the automobile ignition circuit and includes an SCR switchable from "on" to "off" by the disarming circuit to permit ignition. The passive arming circuit includes a Darlington amplifier configuration, is interposed in the automobile ignition circuit, and is coupled through an exit delay circuit to the remaining circuit portions of the device: interval timing and activating circuit, square-wave generator, trigger, entrace delay and siren circuits. The amplifier configuration supplies power to operate the circuits until switched by proper actuation of the disarming circuit and automobile ignition.

Abstract: An alarm device for the deterrence of burglary and theft from an automobile is disclosed. The device provides a voltage responsive trigger, a digital activating circuit and a "high-low" siren output. The device also includes arming circuits for arming and disarming the device, various delay and timing cicruits and means for connection to present day automobile electrical systems.