Programmable vehicle anti-theft system
First Claim
1. A programmable security system for a device having a lock operable by a key, comprising erasable memory means for storing a code associated with a valid key and for storing a key status code indicative of whether the previous attempt to operate the lock was initiated with a valid key or an invalid key, means for reading an input key code in response to a predetermined step in the operation of the lock by said key, means for comparing the input key code with the stored key code to permit operation of the device when the input key code matches the stored key code and the key status code indicates that the previous attempt to operate the lock was initiated with a valid key.
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Accused Products
Abstract
A vehicle anti-theft device is disclosed which includes an electronically erasable programmable read only memory (EEPROM) which stores a modifiable code which must be matched by an input code in order to start the vehicle. The ignition key includes a resistor pellet, engaged by contact in the ignition lock assembly, which is measured to provide the input code. To avoid problems associated with intermittent contact engagement with the resistor pellet, circuitry is provided to control the resistor measurement cycle.
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Citations
10 Claims
- 1. A programmable security system for a device having a lock operable by a key, comprising erasable memory means for storing a code associated with a valid key and for storing a key status code indicative of whether the previous attempt to operate the lock was initiated with a valid key or an invalid key, means for reading an input key code in response to a predetermined step in the operation of the lock by said key, means for comparing the input key code with the stored key code to permit operation of the device when the input key code matches the stored key code and the key status code indicates that the previous attempt to operate the lock was initiated with a valid key.
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9. In a programmable security system for a motor vehicle having an ignition lock operable by an ignition key containing a resistor pellet, the ignition lock including contacts which are engaged by the resistor pellet when the key is inserted in the lock, the improvement comprising erasable memory means containing a first register for storing a key code and a second register for storing a first key status code if a valid key was used on the previous attempt to operate the lock and a second key status code if an invalid key was used on the previous attempt to operate the lock, analog to digital converter means for sampling and converting the value of the resistor pellet to one of a predetermined number of input key codes, means of accepting the value of the resistor pellet as valid only if a predetermined number of samples of the resistor value corresponds to one of said predetermined key codes, means for comparing the input key code with the stored key code to permit operation of the motor vehicle if the input key code matches the stored key code unless an invalid key was used in the previous attempt to operate the lock and a predetermined interval of time has not passed since the previous attempt.
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10. A programmable security system for a device having a lock operable to a key, comprising erasable memory means for storing a code associated with a valid key, said memory means including status code storage means for storing a key status code indicative of whether an attempt to operate the lock was initiated with a valid key or an invalid key, means for reading an input key code in response to a predetermined step in the operation of the lock by said key, means for comparing the input key code with the stored key code to permit operation of the device when the input key code matches the stored key code, timer means, means for activating said timer means to prevent operation of the device for a predetermined time interval when the input key code does not match the stored key code, means responsive to application of power to said system for activating said timer means if said status code storage means indicates that the last attempt to operate the lock was initiated with an invalid key.
Specification