| 摘要 |
<p>Apparatus for detecting intruders in an off-limits area, such as a railway track bed, comprises vibration means and signal analyzing means. The vibration pick-up means picks up vibrations caused by intruder contact and generates an electrical signal correlatable with such vibrations. The signal analyzing means includes selecting means for selecting a subsonic portion of the signal, and measuring means for measuring one or more parameters of the subsonic portion and for generating an alarm signal. The vibration pick-up means preferably comprises a coaxial cable coupled to a row of contact plates each supported on resilient support means and tuned to resonate in response to subsonic driving frequencies caused by human beings falling onto or walking on the contact plates.</p> |
