Vehicle anti-theft system

A vehicle anti-theft system comprising:

• a theft detection unit for discriminating whether or not a signal supplied to the input thereof is an ID signal representing a right start-up operation, and generating a verification signal if it is a right ID signal while generating a theft signal if it is not, said verification signal being a pulse having a predetermined cycle and duty ratio;
• a start-up enable signal generating means including an input port connected to said theft detection unit, said start-up enable generating means generating a start-up enable signal when said verification signal is supplied on said input port;
• an engine control unit responsive to said start-up enable signal for performing the start-up control of the engine;
• a discrimination timing signal generator for generating a level discrimination timing signal which indicates the timing of the level discrimination of the output signal from said theft detection unit;
• signal level sensing means for generating a signal representing the level of the output signal from said theft detection unit at the time of generation of the discrimination timing signal;
• means for sensing the level inversion of said output signal;
• and
• a counter for counting the number of the sensed level inversions, and generating an output when the count value reaches a predetermined value, wherein
• said start-up enable signal generating means generates said engine startup enable signal in response to the output of said counter.

A vehicle anti-theft system comprising:

• a theft detection unit for discriminating whether or not the signal supplied to the input thereof is an ID signal representing a right start-up operation, and generating a verification signal if it is a right ID signal, while generating a theft signal if it is not;
• a start-up enable signal generating means for generating a start-up enable signal in response to said verification signal;
• and
• an engine control unit supplied with said start-up enable signal and responsive to said signal for performing the start-up control of the engine, while, when supplied with said theft signal, disabling the start-up control of the engine;
• timer means for generating a timer signal after the elapse of the predetermined discrimination time during which the output signal from said theft detection unit is discriminated;
• and
• discrimination means for discriminating the input signal to a port connected to said theft detection unit in response to the generation of the timer signal, and activating said start-up enable signal generating means to generate an engine start-up enable signal when said input signal indicates that said theft detection unit is not operating normally.

A vehicle anti-theft system comprising:

• a theft detection unit for discriminating whether or not the signal supplied to the input thereof is an ID signal representing a right start-up operation, and generating a verification signal if it is a right ID signal, while generating a theft signal if it is not;
• a start-up enable signal generating means for generating a start-up enable signal in response to said verification signal;
• and
• an engine control unit supplied with said start-up enable signal and responsive to said signal for performing the start-up control of the engine, while, when supplied with said theft signal, disabling the start-up control of the engine,
• a discrimination timing signal generator circuit for generating a level discrimination timing signal which indicates the timing of the level discrimination of the output signal from said theft detection unit;
• a signal level sensing means for generating a signal representing the level of the output signal from said theft detection unit at the time of generation of the discrimination timing signal;
• a means for sensing the level inversion of said output signal;
• and
• a counter for counting the number of the sensed level inversions, and generating an output when the count value reaches a predetermined value, wherein
• said start-up enable signal generating means generates said engine start-up enable signal in response to the output of said counter.

A vehicle anti-theft system comprising:

• a theft detection unit for discriminating whether or not a signal supplied to the input thereof is an ID signal representing a right start-up operation, and generating a verification signal if it is a right ID signal while generating a theft signal if it is not;
• a start-up enable signal generator including an input port connected to the theft detection unit, said enable signal generating means generating a start-up enable signal when said verification signal is supplied on said input port;
• an engine control unit responsive to said start-up enable signal for performing the start-up control of the engine;
• and
• a destructive action detection means for detecting a destructive action on said theft detection unit, and generating a destruction signal when a destructive action is detected;
• said start-up enable signal generator being inhibited from generating a start-up enable signal when the destruction signal is generated, even if said verification signal is being supplied on said input port.

A vehicle anti-theft system comprising:

• a determination signal generating means for outputting a verification signal or a theft signal on a determination signal line if an externally inputted ID code is a right ID codes, or is not a right ID code, respectively,
• a fault signal generation means for generating a fault signal on the determination signal line if a signal level is uncertain on the determination signal line,
• a dummy line disposed along the signal lines constituting said determination signal generating means so that it is certainly broken if said signal lines are broken, the signal level on the signal line becoming indefinite when said signal lines are broken,
• a break detection means for detecting a break in said dummy line, and
• an engine control means for permitting the engine control in response to said verification signal and fault signal, and inhibiting the engine control in response to said theft signal, while for inhibiting the engine control independently of the determination signal when a break in said dummy line is detected.

In a vehicle anti-theft system supplied with an operating power through a battery line comprising,

• a determination signal generating means for outputting a verification signal or a theft signal on a determination signal line if an externally inputted ID code is a right ID codes, or is not a right ID code, respectively,
• a fault signal generation means for generating a fault signal on the determination signal line if a signal level is uncertain on the determination signal line,
• an engine control means for permitting the engine control in response to said verification signal and fault signal, and inhibiting the engine control in response to said theft signal,
• a vehicle anti-theft system further comprising a history detection means for detecting the history of the disconnection of said vehicle anti-theft system from the battery line, wherein
• said engine control means inhibits the engine control independently of said determination signal when said disconnection history is detected by said history detection means.