| 摘要 |
PURPOSE:To enable the control between the maximum volume and minimum volume determined by a viewer, by exercising the control of a control signal with its pulse width varied on a remote volume controller. CONSTITUTION:One control signal with its pulse width varied is inputted to the volume control input ot turn ON-OFF transistor Tr7. While Tr7 is OFF, capacitor C4 is charged via variable resistance 1 and fixed resistance R2, and while Tr7 is On, on the other hand, the chrge of C4 is discharged via R2 and R3. As for input- output characteristics of sound amplifier 9, supplying a volume control signal from the remote controller results in that the input of amplifier 9 will be at maximum and its output will be at minimum with Tr7 OFF since the output voltage decreases as the input voltage increases. As shown by lines (a), (b) and (c), they concentrate upon one point with the sound control input small, so that minimum sound will be fixed and the maximum sound will depend upon resistance 1. The control between this maximum sound and minimum sound is exercised with a control signal. |
