| 摘要 |
PURPOSE:To prevent the forgery and piracy, by making impossible the reproduction at normal means, through the provision of the means forming the protection film on the magnetic recording medium and saturating magnetically the protection film of the recording medium to the head in common use of recording and reproduction. CONSTITUTION:On the magnetic recording magnetic film 12 formed on the base 11, the protection film 13 by the ferromagnetism of small coercive force is formed. Further, the magnetism saturation coil 43 is provided to the head core 4 providing the recording coil 41 and the reproduction coil 42. At magnetic recording, the fine DC current in which the ferromagnetic film 13 is in magnetic saturation is fed to the magnetic saturation coil 43. At reproduction, no magnetic flux change is taken place to the gap of the head core 4, if the ferromagnetic film 13 is not in magnetic saturation state, and when fine DC current is fed to the magnetic saturation coil 43, the residual magnetism in the magnetic film 12 is appeared as the magnetic flux change to the reproduction coil 42 and the content of recording is picked up with greater output signal and can be reproduced. |
