| 摘要 |
A security system to prevent unauthorized starting of the engine of a vehicle has a remote control unit (18) equipped with a transponder which, on reception of an interrogation signal using at least one reception aerial (20), transmits an identification code group using a transmitter unit (40). Located in the vehicle is a control unit (12), which on actuation of a starter button (26) within the vehicle, transmits the interrogation signal, and subsequently checks the identification code group transmitted by the remote control unit. Starting of the engine will only be possible when the identification code group coincides with the code group expected by it. Connected to the reception aerial (20) is a signal detector (28), which has a reaction threshold level that can be toggled between a high value and a low value. This signal detector will relay the interrogation signal to further processing stages only when the interrogation signal level exceeds the set reaction threshold.
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