Importance

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Abstract

A copy protected magnetic storage disk includes a plurality of record tracks suitable for recording information-bearing data accompanied by a clock signal having a signal strength corresponding to the signal strength of the data. At least one of the record tracks includes a recording pattern representative of a code burst derived by temporarily changing the clock signal during a recording operation. Upon playback, the recording pattern of the code burst causes a random series of playback data to be produced which are dissimilar from one playback operation to the next playback operation. To verify the status of a disk (original or a copy), the code burst is read twice. With an original disk, the playback data is dissimilar; each time a copy is read, however, the same playback data is produced.

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First Claim