| 摘要 |
PURPOSE:To keep constant the relative speed between the playback head and the disc, by controlling the disc number of revolutions, according to the detected value of number of revolutions of disc, via the pulse motor and electronic circuit driving the playback head. CONSTITUTION:When the recording and playback head 6 is located at the initial position of outermost circumference, the count circuit 10 is reset to zero with the signal of the switch 16. Next, the pulse motor 8 is driven with the driving pulse from the driving pulse power supply 9 and the playback head 6 is radially moved via the feeding screw rod 7 and the head holder 5. The pulse fed to the pulse motor 8 is counted at the count circuit 10, and the motor 4 is driven with the voltage corresponding to the location on the disc 2 radius of the playback head 6. The output of the pulse generator 14 at the motor 4 to detect the number of revolution of the motor 4 is fed back to the motor driving section through the frequency voltage converter 14. Thus, the relative speed between the playback head 6 and the disc 2 can be kept constant. |
