| 摘要 |
PURPOSE:To realize the level setting featuring a small amount of the inter-channel deviation by installing the signal attenuator groups to each transmission line and then giving the control to the these signal attenuation quantity via the common digital signals. CONSTITUTION:With push of UP-switch, monostable multivibrator 25 is triggered to generate one unit of the pulse. This pulse is supplied to the UP input terminal of counter 23. Thus the UP counting is given to counter 23, output A is turned to H, analog switches 9 and 30 conduct, and the resistance attenuator of the 1st step is set under the attenuation state for resistance attenuator groups 3 and 6 each to give attenuation of, for example, 1dB. Then in case attenuation of, for example, 3dB is given, switch 24 is pushed three times. In this case, three units of the pulse are generated from monostable multivibrator 25 are generated to be applied to the UP input terminal of counter 23. Thus output A and B of counter 23 are turned to H along with output C and D turned to L each. Accordingly, switches 9, 13, 30 and 34 conduct, and the attenuators of 1st and 2nd steps are attenuated to give the attenuatton quantity to the both channels. While DOWN-switch 27 is pushed when the increment of the sound volume is desired. |
