Siemens Aktiengesellschaft

Peter Voelkl

Manfred Glehr

Stefan Haimerl

In an anti-theft system for a motor vehicle, an oscillating circuit of a transceiver in the motor vehicle is modulated with code information of a portable transponder. A demodulator detects the code information and carries it onward to a computer unit, where it is checked for authorization. Component tolerance or temperature changes can mean that initially no code information will be demodulated, despite a properly functioning transponder. According to the invention, the frequency of the modulated oscillation is then measured and reregulated to a command frequency.

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Tegernheim, Germany

Peter Voelkl