| 摘要 |
Intrusion detection apparatus for use in perimeter security systems and the like is provided with multiple channel signal processing. Each signal processor includes a bandpass filter whose passband is selectable. Each is respectively responsive to sensed movement including vibrations within the associated selected passband. An output affirmative signal is generated if the amplitude of the input signal constituent within the associated frequency range exceeds a threshold level for a predetermined period of time. A logic circuit receives the outputs of all of the signal processors and provides an output alarm signal when a predetermined combination of affirmative signals is received from the signal processors. Such logic circuit preferably works with digital signals obtained by analog-to-digital conversion. A threshold bias adjustment may be provided for adjusting the threshold amplitude of at least one input signal so that ambient noise may be taken into consideration by the logic circuit so that as ambient noise increases the tendency otherwise present to generate a false alarm will be impeded.
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