| 摘要 |
PURPOSE:To prevent a malfunction of a pickup to a turntable, by confirming a light emitting state of a light emitting element for detecting the diameter of a record. CONSTITUTION:Light of light emitting elements 4, 5 is cut off by the record diameter, and is constituted so that it does not reach photodetectors 6, 7. Also, in case when there is no record on a turntable 1, the light of the light emitting elements 4, 5 reaches the photodetectors 6, 7. When these light emitting elements 4, 5 are lighted normally, a contant current flows to the light emitting elements 4, 5, therefore, bythis current, a potential difference is generated across a resistance 9, but when the current does not flow due to disconnection, etc. and they are not lighted, no current flows to the resistance 9, too, and no potential difference is generated. Accordingly, by the potential difference of the resistance 9, a lighting state of the light emitting element can be confirmed, and it is prevented that a pickup descends onto the turntable by mistake. |
