Dual status magnetic marker having magnetically biasable flux collectors for us in electronic article surveillance systems
First Claim
1. A dual status marker for use in an electronic surveillance system in which there is produced in an interrogation zone an alternating magnetic field, said marker comprising at least one piece of low coercive force, high permeability responder material configured to have at least one center section and flux collectors proximate to each end of each said center section and pieces of remanently magnetizable keeper material positioned proximate to at least certain of said flux collectors, whereby when said pieces of keeper material are magnetized, localized fields result which bias the magnetization in said certain flux collectors and results in an altered response of the marker to said applied field compared to that resulting when said pieces of keeper material are unmagnetized.
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Abstract
A dual status marker for use in electronic article surveillance systems having an alternating magnetic field. The marker comprises a magnetic responder element having a central switching portion and flux collectors on each end which concentrate flux within the switching portion to ensure that the flux density therein is sufficient to generate an approximate response. The marker is made dual status by providing magnetizable keeper elements adjacent the flux collectors. When the keeper elements are magnetized, the associated field biases the flux collectors and inhibits magnetization reversal therein in response to an interrogation field, thereby preventing flux from the interrogation field from being concentrated in the switching portion of the responder element.
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Citations
13 Claims
- 1. A dual status marker for use in an electronic surveillance system in which there is produced in an interrogation zone an alternating magnetic field, said marker comprising at least one piece of low coercive force, high permeability responder material configured to have at least one center section and flux collectors proximate to each end of each said center section and pieces of remanently magnetizable keeper material positioned proximate to at least certain of said flux collectors, whereby when said pieces of keeper material are magnetized, localized fields result which bias the magnetization in said certain flux collectors and results in an altered response of the marker to said applied field compared to that resulting when said pieces of keeper material are unmagnetized.
Specification