A multi-frequency resonant tag circuit for use with an electronic security system having improved noise discrimination

For use in an electronic security system which includes means for providing an electromagnetic field of a frequency which is swept within a predetermined range, means for detecting a first frequency within said range, and means for providing an electromagnetic field at a second frequency outside of said range, a multi-frequency resonant tag circuit containing at least first and second tuned circuits respectively resonant at said first and second frequencies comprising:

• a planar insulative substrate having formed on one surface thereof
• a first conductive area centrally formed on said substrate surface;
• a second conductive area formed along one side of said substrate surface;
• a first conductive path arranged on said substrate surface between and in electrical connection with said first and second conductive areas;
• a second conductive path formed on said substrate surface between and in electrical connection with said second conductive area and a third conductive area formed on said substrate surface near a corner thereof;
• and wherein the opposite surface of said substrate includes:
• fourth, fifth and sixth conductive areas each in alignment and substantially coextensive with said respective first, second and third conductive areas formed on said one substrate surface;
• a conductive path connecting said fourth and fifth conductive areas;
• a conductive path through said substrate connecting said third and sixth conductive areas;
• and
• a conductive path interconnecting said fifth and sixth conductive areas and dimensioned to fuse upon application of an electromagnetic field of predetermined power at said second frequency to thereby destroy the resonant properties of said tag circuit at said first frequency.

For use in an electronic security system which includes means for providing an electromagnetic field of a frequency which is swept within a predetermined range, means for detecting a first frequency within said range and means for providing an electromagnetic field at a second frequency, a multi-frequency resonant tag circuit containing at least first and second tune circuits respectively resonant at said first and second frequencies comprising:

• a planar substrate of electrically insulative material;
• a first conductive path formed on a surface of said substrate in a configuration to define a first inductor;
• a second conductive path formed on said substrate in a configuration to define a second inductor;
• first and second pairs of conductive areas formed on said substrate, each pair having conductive areas in alignment on respective opposite surfaces of said substrate to define a capacitor, the conductive areas on the substrate surface containing said first and second conductive paths being electrically connected to said paths at selected points to define said first and second tuned circuits;
• and
• a conductive path provided through said substrate and completing at least one of said tuned circuits by interconnection of said first or second conductive path and one of said conductive areas.

For use in an electronic security system which includes means for providing an electromagnetic field of a frequency which is swept within a predetermined range, means for detecting a first frequency with said range and means for providing an electromagnetic field at a second frequency, a multi-frequency resonant tag circuit containing at least first and second tuned circuits respectively resonant at said first and second frequencies comprising:

• a planar insulative substrate having formed on one surface thereof;
• a first conductive area;
• a second conductive area;
• a first conductive path in electrical connection with said first and second conductive areas arranged in a configuration to define a first inductor;
• a third conductive area;
• a second conductive path in electrical connection with said second conductive area and said third conductive area and formed in a configuration to define a second inductor;
• said planar insulative substrate having formed on a second surface thereof:
• fourth, fifth and sixth conductive areas each in alignment and substantially co-extensive with said respective first, second and third conductive areas formed on said one substrate surface, said first and fourth conductive areas and said second and fifth conductive areas comprising respective first and second capacitors;
• a conductive path connecting said fourth and fifth conductive areas;
• a conductive path through said substrate connecting said third and sixth conductive areas;
• and
• a conductive path interconnecting said fifth and sixth conductive areas;
• said first inductor, second inductor and second capacitor being electrically connected to form said first tuned circuit;
• and
• said first capacitor, second inductor and second capacitor being electrically connected to form said second tuned circuit.