Abstract An alarm condition sensor for enclosing a device to be protected, such as a vault, which will change its electrical properties and thereby facilitate an alarm indication when a person tampers with the sensor and/or attempts to cut, burn or otherwise penetrate the protected device to gain access thereto. The alarm condition sensor includes frangible, opaque panels adhesively secured to the exterior surface of the protected device to completely enclose it. The panels have a printed circuit on the inside surface thereof which is electrically insulated from the exterior of the protected device, and due to the opaqueness of the panel is not visible from the outside. Attempts to pry, fold, bend, or otherwise remove the frangible panel prior to penetration of the protected unit itself will cause the panel, by virtue of its brittleness, to break, interrupting the electrical continuity of the printed circuit formed thereon. Similarly, attempts to drill, cut, or otherwise penetrate the protective panel, which necessarily occur prior to penetration of the protected unit, either interrupt the electrical continuity of the printed circuit or at least shortcircuit it to ground via the vault which is typically of conductive material. In either case, a change in the electrical circuit occurs which can be sensed and an alarm indication provided prior to the point in time when the protective device is actually penetrated.
A penetration-responsive protected assembly comprising: a vault having walls completely enclosing and thereby defining a protected interior, said walls having an exterior surface and being relatively thick to inherently inhibit access to said interior by making a hole therethrough, at least one of said walls being electrically conductive, a protective panel located exterior of said one electrically conductive vault wall, said panel including a. an opaque substrate of brittle electrically non-conductive material which is relatively thin and which inherently possesses low resistance to penetration, said substrate having an inner surface, b. an electrically conductive circuit path secured to said inner surface of said substrate and having predetermined electrical characteristics, c. an electrically insulative adhesive bonding said circuitbearing inner surface of said substrate to said one exterior wall surface to preclude removal of said brittle substrate without altering the electrical characteristics of said printed circuit, and d. an electrical sensing circuit electrically connected to said circuit path to detect interruption of said path and/or shortcircuiting of said circuit path to said one electrically conductive vault wall.
Claim 2
Dependent Claim
175 words
A penetration-responsive protected assembly comprising: a vault having walls completely enclosing and thereby defining a protected interior, said walls having an exterior surface and being relatively thick to inherently inhibit access to said interior by making a hole therethrough, at least one of said walls being electrically conductive, a protective panel located exterior of said one electrically conductive vault wall, said panel including a. an opaque substrate of brittle electrically non-conductive material which is relatively thin and which inherently possesses low resistance to penetration, said substrate having an inner surface, b. an electrically conductive circuit path secured to said inner surface of said substrate and having predetermined electrical characteristics, c. an electrically insulative adhesive bonding said circuitbearing inner surface of said substrate to said one exterior wall surface to preclude removal of said brittle substrate without altering the electrical characteristics of said printed circuit, and d. an electrical sensing circuit electrically connected to said circuit path to detect interruption of said path and/or shortcircuiting of said circuit path to said one electrically conductive vault wall.