Intrusion Detection Apparatus.
DEPARTMENT OF THE NAVY WASHINGTON DC
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A specially configured cable, which, in use, has a cross section which is symmetrical to a vertical line, but asymmetrical to a horizontal line, is used for an intrusion detection system. It comprises an external sheath, which may be round or rectangular in cross section. An inner conductor is positioned below the center of the cable. It is supported in place by a thin, substantially flat, sheet of insulating material, which is attached to the inner surface of the outer sheath. This particular configuration maximizes the change in capacitance caused by an intruder passing over the cable. The cable is connected to a time-domain reflectometer, which can display on a screen the location of the intrusion with respect to an end of the cable as well as the probable type of intrusion. Author
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