The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 03, 1988
Filed:
Jun. 13, 1986
Johannes H Hogen Esch, Aalten, NL;
N.V. Nederlandsche Apparatenfabriek Nedap, De Groenlo, NL;
Abstract
An electromagnetic detection system comprising transmission unit for producing in at least one first detection zone an electromagnetic interrogation field. The system includes a plurality of responders having attachment element for attachment to articles to be protected, each including a resonant circuit and when present in a detection zone, in response to the interrogation field, producing a signal. The system further includes a first detection adapted to detect a responder and, on detection of a responder, to produce a warning signal. According to the invention, the responders are designed in such a manner that when the attachment elements are removed or when a responder is damaged, at least one frequency determining parameter of the responder is changed in a predetermined manner. At least one second detection zone is provided wherein responders with the at least one changed frequency determining parameter can be detected.