Range limited area protection system
US4124848A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 21, 1977 |
| Grant date | Nov 7, 1978 |
| Priority date | — |
| Expiry date | Sep 21, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/12
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A system for detecting intruder motion in selectable zones of a defined area is disclosed. The system is principally used as a line protector to detect intruders in the vicinity of a fence or wall and may be used as a virtual fence by employing a narrow-beam antenna and deep range coverage to detect an intruder crossing its line of sight. The system utilizes a transmitter for periodically sweeping the area to be protected and a receiver incorporating a narrow band filter which is variable to select a plurality of overlapping zones within the protected area, the presence of a reflective target in a selected zone resulting in a corresponding output signal. Means are provided to store such output signals from each zone and to compare received signals with previously-stored signals to detect differences in the target pattern of each zone. Differences exceeding a predetermined threshold level produce event signals which may result in a rescanning of the same zone, the system producing a zone trip signal only if an event is detected in a rescan. Upon completion of a complete scan of all zones, the system responds to selected alarm criteria to produce an alarm indication if there has been…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.