| 摘要 |
A method for degaussing a magnetic storage medium, such as a reel of magnetic tape, is disclosed. In the disclosed method, the reel of magnetic tape is simultaneously rotated on its axis and subjected to an applied transverse magnetic field substantially in the plane of the reel. The transverse magnetic field is applied first in one direction and then in the opposite direction. An axial magnetic field, substantially parallel to the axis of the reel, is then applied, first in one direction and then in the opposite direction. In the preferred embodiment, the step of applying an axial magnetic field includes applying axial magnetic fields in alternating directions at successively decreasing amplitudes. In the disclosed apparatus, the transverse magnetic field is obtained using a lateral coil which passes over and under the reel and covers about half the reel. The axial magnetic field is obtained using a ring-shaped coil surrounding the periphery of the reel. The sequence and characteristics of the applied magnetic fields as disclosed, are useful in obtaining a magnetic storage medium that is completely erased and leaves no significant amount of noise.
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