| 摘要 |
PURPOSE:To detect the recording initiation with high accuracy by using a 1st disk which can be controlled in the circumferential direction of a feed gear, a 2nd disk which revolves at a speed different from the feed gear and can be controlled in the circumferential direction of a rotor, and a detector which detects the coincidence between the through-holes of both disks. CONSTITUTION:The revolving speeds and directions of disks 15 and 16 are decided by an output shaft 8' of a stepping motor 8 via a train of planetary gears. Then the number of these planetary gears and the number of teeth of gears are set so that no coincidence is obtained between through-holes 151 and 161 of both disks as long as the shift value of a head carriage is kept within a range less than the recording area of a magnetic disk. Therefore, the coincidence between both through-holes is obtained only at the recording initiation of the 1st track within the recording area of the magnetic disk. Thus the recording initiation point of the 1st track can always be decided when a detector 17 detects the coincidence between both holes 151 and 161 of disks 15 and 16. In such a way, the recording initiation point of the 1st truck can be easily detected with high accuracy.
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