| 摘要 |
PURPOSE:To improve follow-up characteristics and to prevent deterioration in S/N ratio due to oscillation by changing a pulse-like voltage applied to the motor to a continuous DC voltage, to increase the revolving speed of a motor. CONSTITUTION:When an arm 2 rotates as shown by an arrow B by more than a prescribed extent, a shutter 3 cuts off light traveling from the light emitting element 4a to the photodetecting element 4b of a photocoupler 4. Consequently, a motor 9 is powered up. The motor 9 moves a moving table 6 along a guide rail 5 toward the no voice groove zone at the internal circumference of a record disk 7. When the revolving extent of the arm 2 exceeds the prescribed one, the shutter 3 is disabled to cut off the light, so the photodetecting element 4b photodetects the light from the light emitting element 4a to generate a certain electric signal. The motor 9 is stopped by a pulsating signal from an electric circuit which processes said electric signal. Then, the arm 2 restarts rotating around a pivot 6a as shown by the arrow B. |
