Sensormatic Electronics Corporation

Other

Jon N Weaver

Ezra D Eskandry

David R Humble

George G Pinneo

David L Gentzler

Peter J Lamanna

The present invention relates to a method and apparatus for detecting the presence of a soft magnetic marker in an interrogation zone. This invention utilizes a modulated transmitter carrier signal generated in an interrogation zone. Modulated harmonics of the transmitter carrier signal are detected when a marker is present in the interrogation zone. The modulation detected can be at the same frequency as the modulation of the transmitter signal or a harmonic of the modulation of the transmitter signal. Detection of the modulation allows higher signal to noise ratios and therefore reduces false detections.

Anti-shoplifting security system utilizing a modulated transmitter signal

This invention relates to detecting the presence of a soft magnetic marker in an interrogation zone. A low frequency electromagnetic field is produced utilizing dual frequency generators causing the magnetic marker to produce a phase shift of the modulation of transmission harmonics. These signals are readily distinguished from ferrous alloys and noise.

Anti-shoplifting security system

A microstrip antenna is incorporated in a floor mat, the latter consisting of a conductive grid laminated to a conductive sheet with a layer of dielectric material therebetween to form a capacitor. The microstrip antenna is connected to a source of microwave energy for the purpose of radiating a microwave signal through a surveillance area. A low frequency signal is applied to the capacitor section of the mat for direct capacitive coupling through the body of a pedestrian to any surveillance tag carried thereupon.

Surveillance system employing a dual function floor mat radiator

A surveillance marker has a semiconductor connected between arms of a dipole antenna, one arm being of non-ferrous conductive material and the other of high permeability low coercivity material such as permalloy. Higher coercivity magnetizable pieces are disposed adjacent the low coercivity arm, and all is sandwiched between paper or other insulating layers. The marker is detected by a combination of RF field and low frequency magnetic field generating and receiving units that energize a master alarm only when both units simultaneously detect the marker signals. Magnetizing the higher coercivity pieces suppresses a signal that would otherwise be reradiated by the marker from the high permeability arm thereby rendering the marker undetectable.

Combined radio and magnetic energy responsive surveillance marker and

A continuous loop transmitting winding assembly is disposed in one panel and a vertically oriented figure eight receiving coil winding assembly is disposed in a second panel, the two panels being mounted on pivots for swinging gate type movement straddling the pathway to be controlled by a magnetic surveillance system. This arrangement confines the surveillance field to the pathway and tends to follow the passage of an object bearing a marker therealong. No marker detecting backfield is generated. Alternatively, one winding assembly is moveable while the other is stationary thereby similarly confining the field. Special winding configurations are used to reduce interference from third harmonic signals produced in adjacent metallic counters. The arrangement also imposes immunity to signals emanating from cash registers, motors and the like. Door and single gate mounted magnetic and microwave surveillance systems are also disclosed.

Electrical surveillance apparatus with moveable antenna elements

Apparatus for detecting the presence within a surveillance zone of a body of high permeability material creates a surveillance field varying sinusoidally at a fundamental frequency. Parallel filter channels select the second and third harmonic components of the perturbations created by said material when present in the field and the phase of the second harmonic relative to a reference signal is compared. The signal level of each of the second and third harmonic components as well as the aforesaid phase congruency cooperatively control an alarm circuit. Rhomboid shaped transmitter coils surrounding figure '8' receiver coils improve coupling to the high permeability body.

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Boca Raton, FL, United States of America

Jon N Weaver