| 摘要 |
PURPOSE:To prevent a disk from deforming through simple circuit constitution by moving up and down the disk by utilizing the discharge of a capacitor which is charged to a source voltage for downward movement between two power sources which move up and down the disk. CONSTITUTION:If a power failure occurs while a support is elevated, a positive source voltage (Vcc) applied to the emitter of the 2nd PNP digital transistor (TR) drops, so the TR is cut off between the collector and emitter. At this time, a diode D1 is turned on with the negative charge from the capacitor C to hold the base potential of the 1st PNP digital TR17 minus, so the TR turns on. On the other hand, the emitter side of a PNPTR15 is also held at a minus potential by the capacitor C, so it turns on. Consequently, a transient current flows in the order of the earth 20, a DC motor 2, a resistance R4, the PNPTR15, and the capacitor C and a DC motor 2 reverses to disengage a drive gear 3 and a friction gear 7 from each other, thereby lowering the support.
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