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:
Nov. 01, 1983
Filed:
Sep. 04, 1981
George G Pinneo, Fort Lauderdale, FL (US);
Jon N Weaver, Boca Raton, FL (US);
Sensormatic Electronics Corporation, Deerfield Beach, FL (US);
Abstract
A surveillance marker has a semiconductor connected between arms of a dipole antenna, one arm being of non-ferrous conductive material and the other of high permeability low coercivity material such as permalloy. Higher coercivity magnetizable pieces are disposed adjacent the low coercivity arm, and all is sandwiched between paper or other insulating layers. The marker is detected by a combination of RF field and low frequency magnetic field generating and receiving units that energize a master alarm only when both units simultaneously detect the marker signals. Magnetizing the higher coercivity pieces suppresses a signal that would otherwise be reradiated by the marker from the high permeability arm thereby rendering the marker undetectable.