Abstract: A tamper resistant reciprocal cylinder lock comprising mutually engageable structures on the lock sleeve and bolt keeper having the capacity to increase the resistance of the lock sleeve forward portion from disengagement with the lock sleeve inner portion when the lock and keeper mechanism in a locked position are under physical attack.

Abstract: Tamper-resistant features are provided for a vehicle hood-locking and ignition disabling apparatus which functions as an automotive anti-theft device. These tamper resistant features are responsive to efforts to defeat or by-pass the anti-theft device and comprise: 1. a magnetically-operated alarm; 2. a lock "breakaway" portion responsive to efforts to break or pull the lock portion of anti-theft device; and 3. an underhood dead latch assembly adapted to dead-bolt the hood of the vehicle in a closed position, and to latch the ignition-disabling circuitry in a closed position.

Abstract: A vehicle alarm system sensing unauthorized use of the vehicle and providing a warning signal for a predetermined warning time interval which may be extended as desired. A latching circuit includes a bistable flip-flop with a capacitor discharging through a voltage divider circuit to define an extended warning time interval. Logic gates are switched to change the voltage divider circuit voltage reference levels to charge the capacitor during a predetermined exit time interval to inhibit warning signal actuation when exiting the vehicle. A re-entry timer is included to inhibit warning signal actuation when re-entering the vehicle.