| 摘要 |
1,218,515. Erasing magnetic disc records. SONY CORP. 11 March, 1969 [11 March, 1968], No. 12691/69. Heading G5R. A magnetic disc record is erased by at least one pair of erase heads 19a, 19b fed with a progressively decreasing D.C. supply 20 so as to produce fields of opposite polarity such that on relative rotation the record is subject to a decaying, alternating magnetic field. The heads 19a, 19b may be fixed or rotatable, and are fed from a switched R-C circuit whose parameters are selected such that the supply decays after 10 to 60 relative revolutions of the disc and heads. A spiral track is recorded by head 13 and leadscrew 16. |
