| 摘要 |
In this device, which is particularly intended to prevent shoplifting, interrogation coils generating electromagnetic fields in the surveillance area can be coupled via security strips existing in the surveillance area to verification coils (10, 10'), at the terminals of which an electric signal indicating the presence of a security strip can be picked up, which is amplified by an electric circuit arrangement (11) and evaluated. To prevent false alarms which are triggered, in particular, by interfering metal parts in the surveillance area, in each case two signal processing channels (30, 30' and 31, 31') comprising parallel-connected amplifier and filter stages are provided for each verification coil (10, 10') in the circuit arrangement (11), the filter characteristics of in each case one signal processing channel (30, 30') being tuned to the useful signal originating from the security strip and of in each case one signal processing channel (31, 31') being tuned to interference signals. <IMAGE>
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