| 摘要 |
PURPOSE:To attain more accurate control in comparison with a mechanical type, by playing positions between the ''lead-in'' in starting record disc playing and the ''lead-out'' at the end of playing continuously and repetitively. CONSTITUTION:A sensor arm is fitted to a position shown in a figure (a) when an arm is at the ''REST'' position. The light axis of a photocoupler comprising light emitting and photodetector elements 86, 87 is interrupted with the sensor arm 49. With this state, the ''REST'' position is detected. When the arm turns toward the center of the record disc, the sensor arm 49 is also turned and when a photodetector 52 comes above a light emitting element 79, the optical axes are coincident to detect the ''LEAD-IN'' position. The element 79 is set so that a pickup stylus comes just above an outer circumference lead-in groove of a 30cm record disc, and the element 80 is set to that of a 25cm record disc and the element 81 is to that of a 17cm record disc, respectively. |
