| 摘要 |
At least two transmitter/receivers 14, 16, 18 are mounted in the vehicle. These send a coded signal to the transponder 22 which replies with a further coded signal. The transponder uses travel time differences or field strength differences in the signals received from the two transmitters to determine its position. Otherwise, the travel time differences or field strength differences in the signals received from the transponder at the two transmitter/ receivers are used to locate the transponder in the car. A further embodiment involves directional transmitter/receivers emitting coded signals. The release component uses the codes to recognise the transmitters from which it is receiving and thus deduce its position (see fig. 3). An indicating unit 20 may indicate whether the transponder is to be found on the left or the right hand side of the car. Also described is a system whereby a single transmitter transmits a search signal and, on receiving this signal, the transponder emits a signal to be perceived directly by a person.
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