Non-erasable magnetic data storage method

摘要

A method for inscribing data onto a magnetic medium (12) wherein portions of an oxide coating (16) of the medium are removed from the medium (12) to create voids (88) while the oxide coating (16) is left undisturbed on areas adjacent to the voids (88). The adjacent areas are then uniformly magnetized. When the medium is moved past a read head (78), changes in magnetic field present at transition points (82) and (84) between the voids (88) and the uniformly magnetized oxide coating (16) of adjacent areas cause a current to be induced in a coil (80) of the read (78) head which current is interpreted by conventional read circuitry as being a data bit. The data inscribed by this method is not erasable by conventional means. The inventive method may be practiced upon selected portions of a medium (12) such that non-erasable data areas and conventional magnetically erasable data areas can coexist on the same medium (12).