| 摘要 |
PURPOSE:To prevent a large output from being generated suddenly from a loudspeaker by automatically moving a volume control unit to a preset position when the power is put to work. CONSTITUTION:When the power is put to work, reference voltage V1 of preset resistor 10 is compared 13 with voltage V2 of volume 2 detector 11 coupling direct with volume controller 2 so as to obtain voltage + or -V3. Judging circuit 12 judges whether this voltage is within the range of preset voltage + or -V0 and when so, control circuit 40 drives motor 8 to shift volume detector 11 into the set range of voltage + or -V3. Simultaneously, loud-speaker 4 is connected by switching control circuit 19. Thus, volume controller 2 moves to a position set by the preset resistor and then the loudspeaker is connected, so that no large output will suddenly be generated from the loudspeaker in power feed. |
