| 摘要 |
PURPOSE:To obtain the audio equipment by invalidating sound volume balance adjustment so as to prevent deficient sound volume and mute phenomenon when only a front speaker is connected. CONSTITUTION:When a 2nd speaker 6b at a rear side is not connected, a voltage level of a signal through a speaker presence detection resistor 7 and a low pass filter 8 goes to a high level, a transistor(TR) 9b of a switching circuit 9 is turned on and TRs 9e, 9f are turned off, a connecting point of 1st and 2nd fader variable resistors 4a, 4b is set open to invalidate the adjustment. Thus, sufficient sound is outputted from 1st and 3rd speakers 6a, 6c in the front side without sound volume adjustment. |
