Electric anti-theft security system

Claim 1

An anti-theft system for a vehicle having a power supply source, comprising: an anti-theft security switch for controlling the power supply to various electrical circuits of the vehicle; a motorised security device comprising a blocking member and an electric drive motor coupled to the blocking member for displacing the latter between a locked position and an unlocked position; and an electronic central anti-theft unit connected electrically to the said anti-theft security switch and to the said motor, the central anti-theft unit being adapted to control operation of the anti-theft system, wherein the said anti-theft security switch comprises a key interruptor for detecting simulated introduction of a key into the anti-theft switch, and a multiple position control interruptor for connection to said electrical circuits of the vehicle and for controlling the supply of power to said circuits in sequence, the said multiple control interruptor comprising a movable control contact connected to one polarity of the power supply source, and a set of fixed contacts for connection to respective said circuits of the vehicle, the said set of fixed contacts being so disposed as to be contacted successively by the movable control contact of the multiple position control interruptor as the said movable contact is operated with a view to starting the vehicle, the system further including an immobilising device connected between the multiple position control interruptor and one polarity of the said power source; a first power supply interruptor and a second power supply interruptor, each coupled to the motor for operation between an open position and a closed position, and arranged to be open when the system is in its locked and unlocked conditions respectively; and wherein at least one said vehicle circuit is connected to one polarity of the said supply source through the multiple control interruptor and the immobilising device, whereby the supply of power to the said at least one circuit is inhibited except when the system is in its unlocked condition, the key interruptor having a movable contact connected to the said supply source, a first fixed contact connected electrically to the motor through the said first power supply interruptor, for cooperation of the said first fixed contact with the movable contact of the key interruptor in the absence of a key for actuating the key interruptor, and a second fixed contact connected electrically to the motor through the said second power supply interruptor, for cooperation with the said movable contact of the key interruptor in the presence of a said key, and wherein the said central anti-theft unit has a first input for detection of a change of position of the movable contact of the key interruptor, a second input for detection of the locked condition of the system, and a third input for detection of the unlocked condition of the system, the system further including condition detecting means for detecting the locked or unlocked condition of the system and means connecting the said second and third inputs of the central anti-theft unit to the condition detecting means.