Intrusion detection apparatus
First Claim
1. A cable having a vertical plane of symmetry and an axis on this plane which is located below the horizontal center line of the cable, comprising:
- an inner metallic conductor, centered about the axis;
a thin, substantially flat, horizontal sheet of insulating material, disposed parallel to the horizontal center line, which makes contact with and supports the conductor at its center elastically; and
an outer metallic sheath, at least semirigid, which encloses the conductor and the sheet, the flat sheet having its edges attached to the inside surface of the sheath.
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Accused Products
Abstract
A specially configured cable, which, in use, has a cross section which is mmetrical 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.
30 Citations
16 Claims
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1. A cable having a vertical plane of symmetry and an axis on this plane which is located below the horizontal center line of the cable, comprising:
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an inner metallic conductor, centered about the axis; a thin, substantially flat, horizontal sheet of insulating material, disposed parallel to the horizontal center line, which makes contact with and supports the conductor at its center elastically; and an outer metallic sheath, at least semirigid, which encloses the conductor and the sheet, the flat sheet having its edges attached to the inside surface of the sheath. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A cable comprising:
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an outer metallic sheath, configured so as to have a plane of symmetry; a thin, substantially flat, sheet of insulating material, attached at its edges to the sheath, in a plane perpendicular to the plane of symmetry, the perpendicular plane not intersecting the midline of the sheath on the plane of symmetry; and a thin layer of metal deposited on the central part of the insulating sheet so as to not touch the sheath, the layer of metal being closer to the midline than the insulating sheet. - View Dependent Claims (14)
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15. Intrusion detection apparatus, comprising:
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a cable having a vertical plane of symmetry and an axis on this plane which is located below the horizontal center line of the cable, comprising; an inner metallic conductor, centered about the axis; a thin, substantially flat, horizontal sheet of insulating material, disposed parallel to the horizontal center line, which makes contact with and supports the conductor at its center elastically; and an outer metallic sheath, at least semirigid, which encloses the conductor and the sheet, the flat sheet having its edges attached to the inside surface of the sheath; means for terminating the cable in its characteristic impedance; means, connected to the other termination of the cable, for injecting a pulse into the cable which propagates to the end terminating in the characteristic impedance, to be reflected back to the connecting termination if there is an intrusion; and means, also connected to the other termination of the cable, for displaying the transmitted pulse, and the reflected pulse if any, the display means being capable of showing the precise location of the intrusion and its nature. - View Dependent Claims (16)
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Specification