| 摘要 |
Markers in different portions (61, 62) of the interrogation zone (60) of an electromagnetic article surveillance system produce signals (72, 73) with waveforms of different character. In one embodiment, a false alarm minimization method determines the character of the waveform of the signal induced in the detection antenna. A requirement that signals with waveforms of different character be sensed provides greater confidence that the marker is passing through, as opposed to being near one portion of, the interrogation zone. Also, false alarms produced by stationary objects such as metallic door and window frames are eliminated. In another embodiment, the direction in which the marker passes through the interrogation zone is determined. |
