Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1980-11-20
1982-12-21
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
Specific condition
73658, 340526, 340566, G08B 1312
Patent
active
043652395
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.
REFERENCES:
patent: 3763482 (1973-10-01), Burney et al.
patent: 3803548 (1974-04-01), Skujins, Jr.
patent: 3836899 (1974-09-01), Duvall et al.
patent: 3922663 (1975-11-01), Lubke et al.
patent: 3947835 (1976-03-01), Laymon
patent: 4047166 (1977-09-01), Miller et al.
Caldwell Sr. John W.
Nowicki Joseph E.
Stellar Systems, Inc.
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