| 摘要 |
PURPOSE:To make a read output stable by providing a current to a magnetic head and applying a magnetic field smaller than a write magnetic field to decrease magnetical deterioration of a recording signal against external disturbance. CONSTITUTION:A stabilized command is given to a constant current circuit 64 to generate a minute DC current, then a switching signal is given to a circuit 63 to change over alternately the polarity of the minute current. Moreover, a magnetic head 20' is moved at a low speed on the entire face of a disc 1, the minute current is given to a coil 60 to demagnetize the magnetic field on the disc 1. The demagnetized magnetic field is decreased more than the write magnetic field. As a result, a read output obtained from a medium 1 is made uniform and no change is caused by an external disturbance smaller than the demagnetized magnetic field. |
