Article surveillance apparatus and systems for computer data disks
First Claim
1. Article surveillance apparatus for a computer data disk having a recording surface of magnetic material with a predetermined coercivity, the apparatus comprising a ferromagnetic marker material having a coercivity substantially lower than that of the magnetic recording surface, the marker being formed integrally on the disk and so positioned thereon that removal of the marker would render the disk unusable for reproduction of data from the disk.
1 Assignment
0 Petitions
Accused Products
Abstract
An article surveillance marker suitable for use on computer magnetic data disks is disclosed in which the marker, a length of low coercivity, high magnetic permeability ferromagnetic material is integrally formed onto the data disk preferably so as to serve as the concentricity determining factor of the disk, whereby attempted removal or override of the marker renders the disk from unauthorized reproduction. A disk drive sytem is also disclosed with a built-in interrogation zone and write inhibit circuit that insures data originating from the host computer or copied from another marker-protected disk can only be written onto a disk having a marker-protected disk.
31 Citations
16 Claims
- 1. Article surveillance apparatus for a computer data disk having a recording surface of magnetic material with a predetermined coercivity, the apparatus comprising a ferromagnetic marker material having a coercivity substantially lower than that of the magnetic recording surface, the marker being formed integrally on the disk and so positioned thereon that removal of the marker would render the disk unusable for reproduction of data from the disk.
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12. A computer data disk having article surveillance protection comprising:
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a disk substrate having a central aperture; a magnetic recording material formed on the surface of the disk for use in magnetically recording data in a series of tracks concentric with said central aperture, said magnetic recording material having a predetermined coercivity; and a surveillance marker comprised of ferromagnetic material integrally bonded to said disk substrate about the central aperture thereof such that attempted removal of the marker would render the disk unusable for reproduction of data from the disk, said ferromagnetic marker material having a coercivity substantially lower than the coercivity of the magnetic recording material. - View Dependent Claims (13, 14, 15, 16)
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Specification