Intrusion detection system
US4879544A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 4, 1987 |
| Grant date | Nov 7, 1989 |
| Priority date | — |
| Expiry date | Nov 4, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B13/2497
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An intrusion detection system using waves guided by the conductive outer sheath of a coaxial cable. An r.f. signal from a transmitter is supplied between the inner conductor and outer conductor or shield in conventional fashion. Coupled wave devices are spaced along the cable; each coupled wave device transferring r.f. energy between a transmission mode within the cable and a guided mode propagated along the exterior of the conductive outer shield. In one embodiment a second coaxial cable similarly provided with coupled wave devices is spaced from the transmitter cable and has one end connected to a receiver. The change in r.f. coupling between the cables caused by an intruder produces variations in the r.f. energy coupled to the second cable which is detected at the receiver. Alternative embodiments include the use of a single cable with coupled wave devices adapted for both transmission and reception. Further alternative configurations include the use of a leaky coaxial cable, preferably buried, operating in combination with a cable provided with coupled wave devices. In some circumstances a single elongated conductor can support the guided mode. The guided mode can be establishe…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.