This alarm is initially armed by a hidden key switch located inside the car. Once armed, there will be a short delay allowing the driver to exit the car. Thereafter, opening a door or trunk lid will trigger the alarm and following another short interval (to allow for the driver to enter the car and disable the alarm) the horn will be pulsed at a rate of about once per second. After about 2.5 minutes the alarm circuitry will reset itself, ready for another intrusion. The circuit is designed around two CMOS integrated circuits which have a an extremely low power consumption from the car battery.