Antitheft alarm for vehicle - has three switches arranged so that ignition circuit is unaffected if alarm is switched on when vehicle is moving

摘要

The anti-theft alarm has a first switch to switch the alarm on and off and to disable the engine's ignition circuit. A second switch (6,7) disables the ignition circuit (8,9) and is operated via a switching transistor (4) connected to the negative pole of the vehicle's generator (1) when the first switch (13,20) is operated and connected to the positive pole of the generator when the first switch is not operated. The first switch is a push-button and is connected to a bistable multivibrator (10) via an RC circuit (11,12) whose resistor is large and capacitor small. The second switch is a relay located in the collector circuit of the switching transistor.