05073925 is referenced by 217 patents and cites 9 patents.

An apparatus for the protection of signal copy for preventing unauthorized copying of music software such as records, compact discs and music tape by recording is arranged such that when recording audio signals on a medium, certain supplemental information is added to the audio signal to be recorded, and in the process of copying by reproducing this medium, when the supplemental signal is detected in the reproduced signal, the copying action is stopped to protect it from being copied.

Title
Method and apparatus for the protection of signal copy
Application Number
216495
Publication Number
5073925
Application Date
June 13, 1990
Publication Date
December 17, 1991
Inventor
Kenichi Takahashi
Kyoto
JP
Takanori Senoo
Hirakata
JP
Yutaka Uekawa
Ashiya
JP
Atsushi Nagata
Hirakata
JP
Agent
Wenderoth Lind & Ponack
Assignee
Matsushita Electric Industrial
JP
IPC
G11B 15/087
G11B 23/36
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