Intrusion warning system
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United States of America Patent
Stats
-
Dec 21, 1982
Grant Date -
N/A
app pub date -
Nov 20, 1980
filing date -
Nov 20, 1980
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
An intrusion warning system for protecting a wall or fence, in particular a chain-link fence, against intrusion by cutting through and/or climbing over same. A small-diameter shielded electrical cable, e.g. a coaxial cable or a shielded twisted pair is mounted on the fence and the vibrations of the fence detected by sensing the small electrical field generated when the dielectric material between the conductors of the cable is stressed by the minute flexing of the cable caused by such vibrations. The sensed electric field signal is AM detected, shaped and then processed as to duration and persistence. An alarm indicating an attempted cut-through type of intrusion is activated if a preselected number of signals of very short duration, indicating abrupt disturbances of the fence, are detected. A separate alarm indicating an attempted climb-over intrusion is activated only if the detected signal persists for a period of time longer than that of the signals used for the cut-through indication and is present for a predetermined portion of a preset time period.
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Cited Art Landscape
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