GB1468272A - Perimeter surveillance system - Google Patents

Abstract

1468272 Surveillance system CONTROL DATA CANADA Ltd 1 Oct 1974 [28 Feb 1974] 42488/74 Headings G4H and G4N A detection system for locating targets which reflect or absorb electromagnetic energy comprises two spaced leaky coaxial cables 10, 11 extending along a prescribed path, a transmitter 16 connected to one of the cables and a receiver 17 connected to the other. The coupling between the cables is altered by the target, which may be an intruder or a vehicle, and the system includes means 18-25 for processing a signal sent from the transmitter to the receiver to determine the location of the target. The cables are selectively connected to the transmitter and receiver by switches 13 so that the direction of signal propagation may be reversed. The transmitter and receiver are connected via a synchronous detector 18 to a digitizer 19 which computes a sequence of numbers representing the average magnitude of the return signal over a sequence of time intervals. Three low pass digital filters 20-22 and a threshold detector 23 are provided for each number in the sequence, the first and second discriminating between very slow and very fast changes in the return signal and the third integrating the difference in the outputs of the first two. The threshold detectors 23 are used to determine the presence of a change in the return signal associated with a target, whose location is determined from the particular detector which is energized. The detectors are connected to an audible alarm 24 and a visual display unit 25, e.g. a CRT, or a plasma or LED display. Two cables are used with switches 13 so as additionally to provide fault detection and location. Simultaneous location of multiple targets is possible, a flashing symbol being used on the display if they are located at the same point.