| 摘要 |
PURPOSE:To eliminate crosstalk between a main control and a sub control circuit by connecting the main control circuit and a voltage control terminal of a circuit to be controlled by a Zener diode. CONSTITUTION:A main sound volume control circuit 10 consisting of the main control circuit 5 and the zener diode 7 controls a voltage. since a value of a resistor 4 to the sub control circuit 6 is large in this case, the sound volume is made variable from minimum to its maximum values independently of the presence of a sub sound volume control circuit 20 comprising the resistor 4 and the sub control circuit 20 at the outside of the dead band. Further, when the control voltage of the main control circuit 5 is within a prescribed range, the control voltage of the circuit 1 to be controlled is made variable by the sub sound volume control circuit 20.
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