Personnel position indicator system

• Main Authors: JOHN HUDSON, ROGER WILLIAM LESLIE HOYLE
• Format: Patent
• Language: English
• Published: 14.03.1990
• Subjects: ALARM SYSTEMS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDEDFOR ELSEWHERE; CHECKING-DEVICES; GENERATING RANDOM NUMBERS; ORDER TELEGRAPHS; PHYSICS; REGISTERING OR INDICATING THE WORKING OF MACHINES; SIGNALLING; SIGNALLING OR CALLING SYSTEMS; TIME OR ATTENDANCE REGISTERS; VOTING OR LOTTERY APPARATUS

A personnel position indicator system supplies an automatic and periodic indication of the location of one or more security personnel engaged upon a perimeter patrol. The system includes a low power VHF transmitter 50, carried by a security person, and intermittently broadcasting a radio signal at frequent predetermined intervals, a loop aerial 12 placed around a secured area's perimeter and connected to a signal processor 18 which detects the time difference between receipt of the signal at each end 14, 16 of the aerial 12 to determine the position of the transmitter 50 relative to the loop aerial 12. The processor 18 may include a delay circuit 28 operative to delay receipt of the signal from one end of the aerial 12 to avoid complications brought about by overlapping signals. The radio pulse may include a location pulse and an identity code pulse unique to the transmitter. The processor 18 may include a reference oscillator 24, mixers 22, 42, limiters 30, 46, demodulators 32, 48, a pulse detector and position generator unit 34, a decoder 36 and a display 38. The unit 34 may include sample and hold circuitry using digital counters. An alarm may be provided under specified conditions.