Vehicle anti-theft device operation method

摘要

A method relates to an anti-theft device which includes a transceiver (1) located in the vehicle, a portable transponder(2) which carries code information and which sends this back to the transceiver in a response code signal, following receipt of the interrogation code signal. Also included is a comparison unit (12) for comparing the detected code information with a specified code information, and a control unit, the latter generating a release signal when agreement of the two sets of information is achieved. A first part of the response code signal is scanned at given times (t0,t1) within a first time slot, that is considerably shorter than the time required for transmission of the complete response code signal. The response code signal is fully scanned when the amplitudes of the response code signal in the first time slot are above a given threshold.