Security tag for use with article having inherent capacitance
US5276431A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 29, 1992 |
| Grant date | Jan 4, 1994 |
| Priority date | — |
| Expiry date | Apr 29, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B13/2442
- WIPO fieldControl
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.