(19)
(11) EP 0 431 745 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
21.11.1991 Bulletin 1991/47

(43) Date of publication A2:
12.06.1991 Bulletin 1991/24

(21) Application number: 90311821.4

(22) Date of filing: 29.10.1990
(51) International Patent Classification (IPC)5: G08B 13/24
(84) Designated Contracting States:
DE ES FR GB IT SE

(30) Priority: 08.12.1989 US 447684

(71) Applicant: MINNESOTA MINING AND MANUFACTURING COMPANY
St. Paul, Minnesota 55133-3427 (US)

(72) Inventors:
  • Montean, Samuel, c/o Minnesota Mining and
    St. Paul Minnesota 55133-3427 (US)
  • Schug, Heinrich, c/o Minnesota Mining and
    Hansastrasse 9, W-4040 Neuss 1 (DE)
  • Sanetra, Juergen, c/o Minnesota Mining and
    Hansastrasse 9, W-4040 Neuss 1 (DE)

(74) Representative: Baillie, Iain Cameron et al
c/o Ladas & Parry Altheimer Eck 2
80331 München
80331 München (DE)


(56) References cited: : 
   
       


    (54) Sensitizer for ferromagnetic markers used with electromagnetic article surveillance systems


    (57) An apparatus for use with magnetically based electronic article surveillance systems employing certain types of markers includes a hollow core having a gap in its perimeter, a coil of wire wrapped around a portion of the core, and appropriate circuitry to drive the combination as an electromagnet. The gap configuration produces an external field of large intensity but limited range, such that the magnetizable portion of a marker is magnetized without affecting magnetic states of the article to which the marker is affixed. Depending on the nature of the circuit, the apparatus may be used as a desensitizer of such markers, or preferably as a resensitizer.






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