×

Electromagnetic detection system, as well as a responder for such a system

  • US 4,742,341 A
  • Filed: 06/13/1986
  • Issued: 05/03/1988
  • Est. Priority Date: 06/14/1985
  • Status: Expired due to Fees
First Claim
Patent Images

1. An electromagnetic detection system comprising transmission means producing in at least one first detection zone an electromagnetic interrogation field;

  • a plurality of responders having attachment means for attachment to articles to be protected, each including a resonant circuit and an electric circuit and which, if present in said first detection zone, in response to the interrogation field, produce a signal; and

    detection means associated with said first detection zone adapted to detect the responder and, on detection of the responder to produce a warning signal, characterized in that the responders are designed in such a manner that when the attachment means are removed or when the responder is damaged, at least one frequency determining parameter of the responder is changed in a predetermined manner and that at least one second detection zone is provided wherein responders with the at least one changed frequency determining parameter can be detected;

    each of said plurality of responders having at least one connection wire extending along the edge of each responder, said wire forming an electric connection between a frequency determining component of the electric circuit of the responder and other frequency determining components of the resonant circuit; and

    said resonant circuit includes at least two parallel-connected coils and that the connection wire forms a connection between the two coils and that the connection wire also forms one of the coils.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×