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Field generation and reception system for electronic article surveillance

  • US 5,005,001 A
  • Filed: 04/05/1990
  • Issued: 04/02/1991
  • Est. Priority Date: 04/05/1990
  • Status: Expired due to Term
First Claim
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1. In a system for detecting the presence of a ferromagnetic marker in an interrogation zone, including first and second generating means for generating first and second magnetic fields, respectively, at first and second frequencies, respectively, and wherein said second frequency is substantially lower than said first frequency, the improvement wherein said first generating means comprises means for generating an alternating field at said first frequency and said second generating means comprises means for generating a rotating field at said second frequency.

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