Sensormatic Electronics Corporation

George G Pinneo

Ezra D Eskandry

Douglas A Narlow

Jon N Weaver

Risto Siikarla

Charles W Woolsey

A method is disclosed for effecting electronic article surveillance with a first high frequency signal and a second lower frequency signal, the second signal having a modulation characteristic therewith. Generally rectangular tag devices are attached to said articles for receipt of such signals and for reradiation thereof. The method involves the fabrication of the tag devices by the steps of: (a) providing first and second circuit elements to be of type exhibiting fixed inductive and capacitive reactances; (b) providing a third circuit element to be of type exhibiting voltage dependent capacitive reactance and forming an electrical series circuit of the first, second and third circuit elements; and (c) configuring the first and second circuit elements with respective geometric diversities, whereby the first circuit element extends longitudinally of the device and is of first transverse dimension, and whereby the second circuit element extends longitudinally of the device at least in part jointly spacedly with the first circuit element and is of second transverse dimension substantially exceeding the first transverse dimension, thus effecting predominant different receipt by the first and second circuit elements of the first and second frequency transmitted signals.

Tag device and method for electronic article surveillance

An improved receptor-reradiator, for use in a surveillance system employing a carrier frequency of UHF or higher in combination with a low frequency electrostatic field signal to be modulated on the carrier signal by the reradiator, is provided by an antenna frame wherein the metallic foil of which it is made is divided into three parts. The first part is U-shape of substantially one width and joins to a central portion of substantially reduced width which is predominantly inductive at the carrier frequency. A semiconductor diode, preferably a Schottky barrier diode or PIN switching diode, is connected in said central portion in series therewith. The opposite end of the central portion joins to an enlarged rectangular portion. At the low frequency the component has effectively two capacitive arms, one on each side of the diode, of different surface area to ensure bias signal for the diode. However, at the carrier frequency, the central portion has a high inductive reactance which, in conjunction with the inductive reactance of the U-shape portion, tunes to resonance the total capacitance of the component including that of the diode. The parts are proportioned such that the diode sees at the carrier frequency an inductance on one side and a capacitance on the other side.

Signal receptor-reradiator and surveillance tag using the same

A low current electrostatic generator powers an electrode that, when proximate to the non-conductive outer surface of a surveillance tag, causes an electrostatic discharge to pass through such outer surface from the electrode and to be received by a conductive circuit within the tag. The resulting discharge impressed across the conductive circuit passes through a diode semiconductor included within such circuit to destroy the diode's unidirectional conducting characteristic and thereby deactivate the tag. No exposed conductive terminals are required on the outer surface of the surveillance tag, and the probe need not physically contact the tag to deactivate it.

Non-contact electrostatic deactivator

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.

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Fort Lauderdale, FL, United States of America

George G Pinneo