Abstract: A copyright protection system is provided in which copyrighted articles, such as documents and photos, have associated with the article magnetic material which is detected when the article is copied on a scanner/reproducing machine. The magnetic material may be secured to the article so that it cannot be removed without destroying the article, or the magnetic material may form part of the article. The scanner/reproducing machine is provided with a magnetic detection system for automatically detecting the copyrighted article.

Abstract: A magnetic assembly for detection and authentication of magnetic documents. The magnetic assembly includes a permanent magnet (PM), first and second magnetically soft high permeability pole pieces shaped to form a tapered, variable gap size magnetic circuit with the permanent magnet. The PM is located at a first gap between the first and second pole pieces. A magnetoresistive (MR) sensing element is located at or near the center of a second gap between said first and second pole pieces. The second gap and MR sensing element are proximate a magnetic document to be sensed. An electrical conductor is adjacent to the MR sensing element, but is electrically insulated therefrom. A direct current is passed through the electrical conductor to create a compensating bias field in the MR element which is combined with the bias field generated by the PM.