Patent Document ID: 5561420
Application ID: 08457730

Base Claim:
1. A motor-vehicle lock system comprising: a remote operator separate from the motor vehicle and having a key part having a predetermined bitting, transmitter means actuatable to transmit a main signal containing a changing main code word, and transponder means substantially independent of the transmitter means for receiving an interrogation signal and thereupon generating a callback signal containing a callback code word; a lock provided with a switch and actuatable mechanically by the key part with the predetermined bitting to operate the switch; a central controller in the vehicle connected to elements of the vehicle for actuating same; receiver means in the motor vehicle connected to the controller for receiving the main signal including the main code word, extracting the main code word from the transmitted main signal, comparing the extracted main code word with a predetermined main code word, and sending a release signal to the controller when the extracted main code word corresponds to the predetermined main code word to actuate the elements; and transceiver means in the motor vehicle and connected to the controller for, when the switch is actuated, generating the interrogation signal, receiving the callback signal containing the callback code word, extracting the callback code word from the callback signal, comparing the extracted callback code word with a predetermined callback code word, and sending a release signal to the controller when the extracted callback code word corresponds to the predetermined callback code word to actuate the elements and setting in the transponder a new callback code word based on the main code word.

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Claim 4:
4. The motor-vehicle lock system defined in claim 1 wherein the transmitter means includes a code register capable of outputting a predetermined sequence of code words and steppable through the sequence to output the code words sequentially one at a time, a clock connected to the register for periodically stepping it through the code-word sequence, and output means for modulating a signal with the code word currently being outputted by the register and for transmitting the modulated signal as the main signal; the receiver means including a code register like the transmitter code register, capable of outputting the predetermined sequence of code words, and steppable through the sequence to output the code words sequentially one at a time, a clock like the transmitter clock and connected to the receiver code register for periodically stepping it through the code-word sequence substantially synchronously with the transmitter clock and transmitter register, and input means connected to the receiver code register and to the controller for receiving and demodulating a transmitted main signal, extracting a main code word from the demodulated signal, comparing the extracted main code word with the code word currently being generated by the receiver code register, and generating a release signal and sending it to the controller when the extracted code word not only corresponds to a code word in the code-word sequence but also lies no more than a predetermined number of code words in the sequence away from the code word currently being outputted by the receiver code register.