Motor vehicle antitheft device with audible alarm - uses detectors on doors, bonnet and boot lid to activate electronic circuit which has delay circuits to allow entry and exit

摘要

The anti-theft device uses an electronic circuit to detect unauthorised usage of the vehicle and has an electrical contact connected into the control box circuit of the vehicle to disconnect the electric circuits used to run the engine. An audible alarm is also triggered. Electric contacts are fitted to detect opening of the doors, bonnet, or boot lid of the vehicle. Additional contacts are fitted on the handbrake lever and on the accelerator cable. The electronic circuit is based on two 555 integrated circuit timers which provide timing for entry and exit delays. CMOS logic gates are used for the detector circuits, and if the alarm is activated as output transistor drives a relay operating the electrical system disabling contact.