Security tag for use with article having inherent capacitance

Details Security tag for use with article having inherent capacitance Security tag for use with article having inherent capacitance

1992-04-29

1994-01-04

Peng, John K.

Communications: electrical

Condition responsive indicating system

Specific condition

324675, 340658, G08B 1314

Patent

active

052764311

ABSTRACT:
A security tag for use with an electronic security system is used for attachment to an article having an inherent capacitance such as meat. The security system includes a transmitter for transmitting into a surveilled area electromagnetic energy having a center frequency within a predetermined detection frequency range and a receiver for detecting within the surveilled area the presence of a security tag resonating at a frequency within the detection frequency range in response to the electromagnetic energy. The tag includes a generally planar dielectric substrate having a first side and a second side. Circuitry on the substrate establishes a resonant circuit having a resonant frequency which is initially a predetermined frequency interval above the center frequency of the detection frequency range. Upon attachment of the security tag to the article, the inherent capacitance of the article interacts with the resonant circuit to shift the resonant frequency of the resonant circuit downwardly, closer to the center frequency of the detection frequency range.

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