Erasing device

摘要

An erasing device includes a magnetic head, a drive motor for rotating a magnetic disc relative to the magnetic head, an erase signal source for producing an erase signal which varies periodically, and apparatus for causing the head to generate magnetic fields with the erase signal, wherein the frequency fV of rotation of the magnetic disc and the frequency fE of the erase signal together satisfy the following condition so that no nodes of the erasing fields are fixed at any point on a track of the magnetic disc during a plurality of rotations of the magnetic disc: fE NOTEQUAL (k/2)fV where k is a positive integer.