Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1990-10-09
1992-03-17
Ng, Jin F.
Communications: electrical
Condition responsive indicating system
Specific condition
340658, 340660, 340691, 368 10, G08B 1308
Patent
active
050972537
ABSTRACT:
The present invention relates to a security device having a control box (12) containing an electronic system (50) and a communications loop (14) over which the system transmits a signal. The device is constructed so that the communications loop can extend from the control box across the boundary of a portal such as a door into a sealed enclosure into which access is restricted whereby the loop must be damaged or moved in order for an entry to be made into the enclosure. The device is adapted for detecting unauthorized entries into such enclosures such as rooms or containers and for recording the time at which such entries occur for later reference. Additionally, the device detects attempts to tamper or interfere with the operation of the device itself and records the time at which such events take place. In the preferred embodiment, the security device includes a microprocessor-based electronic system (50) and a detection module (72) capable of registering changes in the voltage and phase of the signal transmitted over the loop.
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Campbell, "Electronic Self-Monitoring Seal", Nuclear Materials Management, 1978 INMM Proceedings, pp. 424-430.
Eschbach Eugene A.
Griffin Jeffrey W.
LeBlanc Edward J.
Battelle (Memorial Institute)
Mullen Jr. Thomas J.
Ng Jin F.
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