Claims
- 1. In an electronic article surveillance system, a method for deactivating a marker that is in a first, activated state, comprising the steps of:
- (a) imparting to the marker a deactivation field having a first, predetermined intensity;
- (b) exposing the marker to an interrogating field, detecting the response produced by the marker, producing an active marker signal if the response indicates that the marker is in the first, activated state, and producing a deactivated marker signal if the response indicates that the marker is in a second, deactivated state;
- (c) imparting to the marker, in response to the active marker signal, the deactivation field having an incrementally greater intensity; and
- (d) repeating steps (b) and (c) until the deactivated marker signal is produced.
- 2. The method according to claim 1 wherein the marker includes at least one magnetizable element.
- 3. The method according to claim 2 wherein the deactivation field comprises a magnetic field which is directionally constant.
- 4. The method according to claim 1 wherein the marker is unmagnetized when in the first, activated state, and magnetized when in the second, deactivated state.
- 5. A deactivating apparatus for deactivating a marker of an electronic article surveillance (EAS) system, the deactivating apparatus comprising:
- interrogation means for interrogating the marker to cause the marker to produce a response, for detecting the response produced by the marker, for producing an active marker signal if the response indicates that the marker is in an activated state, and for producing a deactivated marker signal if the response indicates that the marker is in a deactivated state;
- deactivation means for applying a deactivation field to the marker in response to the active marker signal, wherein the interrogation means re-interrogates the marker after each application of the deactivation field, and wherein the deactivation field intensity is incrementally increased each time the deactivation field is applied; and
- control means for disabling the deactivation means when the deactivated marker signal is produced.
- 6. The apparatus according to claim 5 wherein the deactivation means includes switch means responsive to the active marker signal for automatically and gradually applying current through a rectifier directly from a source of alternating electrical power to incrementally increase the deactivation field.
- 7. The apparatus according to claim 6, wherein magnetic flux density required for deactivating the marker is built up by a plurality of rectified voltage pulses from the source of electrical power.
- 8. The apparatus according to claim 6, wherein the interrogation means interrogates the marker with a substantially sinusoidal interrogation field.
- 9. The apparatus according to claim 8 wherein the interrogation means includes a wave generator and a coil adapted to produce the interrogation field.
- 10. The apparatus according to claim 9, further including a yoke proximate to the coil, and configured to create a relatively wide air gap, with the yoke and the coil being adapted to be mounted underneath a table top.
- 11. The apparatus according to claim 10, wherein the yoke has a substantially U-shaped configuration.
- 12. An apparatus according to claim 9, wherein the coil includes two terminals, and wherein both terminals of the coil are connected through impedance matching and decoupling capacitors to the wave generator, and further wherein the switch means prevents current from the wave generator from being short-circuited.
- 13. An apparatus according to claim 9, further including a yoke proximate to the coil comprised of a relatively low coercive force material.
- 14. The apparatus according to claim 5 wherein the deactivation field is directionally constant.
Parent Case Info
The application is a continuation-in-part of U.S. Ser. No. 07/697,644 filed May 8, 1991, U.S. Pat. No. 5,210,524 issued May 11, 1993.
US Referenced Citations (6)
Foreign Referenced Citations (3)
Number |
Date |
Country |
30 14 667 A1 |
Oct 1981 |
DEX |
30 15 811 A1 |
Oct 1981 |
DEX |
30 45 703 A1 |
Jul 1982 |
DEX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
697644 |
May 1991 |
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