Reradiating EAS tag with voltage dependent capacitance to provide tag activation and deactivation
First Claim
1. A tag for use in an article surveillance system in which a plurality of signals at a plurality of preselected frequencies are established in a surveillance zone, said plurality of signals including a firs signal at a first frequency and a second signal at a second frequency lower than the first frequency, and an alarm is initiated upon detection of a predetermined tag signal reradiated by the tag at a frequency related to the plurality of preselected frequencies, the tag comprising:
- circuit means responsive to said plurality of signals for reradiating said predetermined tag signal, said circuit means being substantially resonant at said first frequency and including;
means for receiving said plurality of signals; and
means responsive to said receiving means for establishing said predetermined tag signal;
and voltage dependent capacitance means in circuit with said circuit means and having a capacitance which can be switched with a change in voltage to selectively enable said circuit means and disable said circuit means from being able to reradiate said tag signal, said voltage dependent capacitance means being arranged relative to said receiving means and establishing means of said circuit means such that, when said voltage dependent capacitance means is switched to a first capacitance value, said voltage dependent capacitance means inhibits said second signal in said plurality of signals from passing from said receiving means to said establishing means to a significantly lesser degree than when said voltage dependent capacitance means is switched to said second capacitance value, thereby enabling said establishing means to establish said tag signal when said capacitance means is at said first capacitance value and disabling said establishing means for being able to establish said tag signal when said capacitance means is at said second capacitance value.
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Accused Products
Abstract
A tag for an electronic article surveillance system which includes a circuit means for reradiating a predetermined tag signal and voltage dependent means in circuit with the circuit means. The voltage dependent means has a capacitance which can be varied with a change in voltage to selectively enable the circuit means and disable the circuit means from being able to reradiate the predetermined tag signal.
56 Citations
39 Claims
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1. A tag for use in an article surveillance system in which a plurality of signals at a plurality of preselected frequencies are established in a surveillance zone, said plurality of signals including a firs signal at a first frequency and a second signal at a second frequency lower than the first frequency, and an alarm is initiated upon detection of a predetermined tag signal reradiated by the tag at a frequency related to the plurality of preselected frequencies, the tag comprising:
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circuit means responsive to said plurality of signals for reradiating said predetermined tag signal, said circuit means being substantially resonant at said first frequency and including;
means for receiving said plurality of signals; and
means responsive to said receiving means for establishing said predetermined tag signal;and voltage dependent capacitance means in circuit with said circuit means and having a capacitance which can be switched with a change in voltage to selectively enable said circuit means and disable said circuit means from being able to reradiate said tag signal, said voltage dependent capacitance means being arranged relative to said receiving means and establishing means of said circuit means such that, when said voltage dependent capacitance means is switched to a first capacitance value, said voltage dependent capacitance means inhibits said second signal in said plurality of signals from passing from said receiving means to said establishing means to a significantly lesser degree than when said voltage dependent capacitance means is switched to said second capacitance value, thereby enabling said establishing means to establish said tag signal when said capacitance means is at said first capacitance value and disabling said establishing means for being able to establish said tag signal when said capacitance means is at said second capacitance value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 32, 33)
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17. An article surveillance system for detecting the presence of an article in a surveillance zone, the system comprising:
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means for generating a plurality of signals at a plurality of preselected frequencies within said surveillance zone, said plurality of signals including a first signal at a first frequency and a second signal at a second frequency lower than the first frequency; a tag comprising circuit means responsive to said plurality of signals for reradiating a predetermined tag signal at a frequency related to said plurality of preselected frequencies, said circuit means being substantially resonant at said first frequency and including means for receiving said plurality of signals and means responsive to said receiving means for establishing said predetermined tag signal; and
voltage dependent capacitance means in circuit with said circuit means and having a capacitance which can be switched with changes in voltage to selectively enable said circuit means and disable said circuit means for being able to reradiate said tag signal, said voltage dependent capacitance means being arranged relative to said receiving means and establishing means of said circuit means such that, when said voltage dependent capacitance means is switched to a first capacitance value, said voltage dependent capacitance means inhibits the passage of said second signal in said plurality of signals from passing from said receiving means to said establishing means to a significantly lesser degree than when said voltage dependent capacitance means is switched to a second capacitance value, thereby enabling said establishing means to establish said tag signal when said capacitance means is at said first capacitance value and disabling said establishing means from being able to establish said tag signal when said capacitance means is at said second capacitance value; andmeans for detecting said tag signal reradiated by said tag. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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34. An article surveillance system in accordance with clam 19 wherein:
said circuit means and said capacitance means are such that, at said first capacitance value of said capacitance means, said circuit means and capacitance means are resonant at said first frequency and, at said second value of said capacitance means, said circuit means and capacitance means are non resonant at said first frequency.
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35. A method for detecting the presence of an article in a surveillance zone, the method comprising:
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generating a plurality of signals at a plurality of preselected frequencies within said surveillance zone, said plurality of signals including a first signal at a firs frequency and a second signal at a second frequency lower than the first frequency; passing a tag into the surveillance zone, the tag comprising;
circuit means responsive to said plurality of signals for reradiating a predetermined tag signal at a frequency related to said plurality of preselected frequencies, said circuit means being substantially resonant at said first frequency and including means for receiving said plurality of signals and means responsive to said receiving means for establishing said predetermined tag signal; and
voltage dependent capacitance means in circuit with said circuit means and having a capacitance which can be switched with changes in voltage to selectively enable said circuit means and disable said circuit means for being able to reradiate said tag signal, said voltage dependent capacitance means being arranged relative to said reciting means and establishing means of said circuit means such that, when said voltage dependent capacitance means is switched to a first capacitate value, said voltage dependent capacitance means inhibits said second signal in said plurality of signals from passing from said receiving means to said establishing means to a significantly lesser degree than when said voltage dependent capacitance means is switched to a second capacitance value, thereby enabling said establishing means to establish said tag signal when said capacitance means is at said first capacitance value and disabling said establishing means from being able to establish said tag signal when said capacitance means is at said second capacitance value; anddetecting said tag signal reradiated by said tag. - View Dependent Claims (36, 37, 38, 39)
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Specification