| 摘要 |
PURPOSE:To eliminate unerased old data regardless of difference in track diameter, and reduce the size of a disk and increase the density arranging the centers of the gaps of a recording and reproducing core and an erasing core symmetrically about an axis running in the center of rotation. CONSTITUTION:The lengthwise center S'' of the gap 11 of the recording and reproducing core is made coincident with a point P1 where the center crosses a track radius R1 at vertical distance L from an X axis, and the azimuth angle alpha is made constant regardless of the radius R1. Further, the center S'' and the center T'' of the gap 12 of two erasing cores are arranged symmetrically about the X axis. Further, while an index hole H is made coincident with an index detection part 20 and a rotation synchronizing signal is generated, an index burst angle is set to theta1, which is varied according to the track radius R1 as shown in a figure. Accordingly, an angle theta1 is provided to be varied according to the radius R1 and the center S'' and center T'' are set on circles having logically the same radius on condition that the azimuth angle alpha is constant regardless of the radius R1, so that no old data is left unerased even when recording and reproduction are performed in an off-track state. |
