| 摘要 |
PURPOSE:To attain automatically excellent matching to a different line length by changing automatically a resistance value and a capacitor value provided to a balanced connection network corresponding to a talking current changed according to the line length. CONSTITUTION:A negative voltage proportional to a talking current is generated across a resistor R1 provided to a talking current supply circuit. The negative voltage is amplified inversely by an inverse amplifier AMPO of a control circuit CONT into a positive voltage, which is divided by resistors R21, R22 and the result is connected to a gate of a transistor (TR0). On the other hand, an output of the amplifier AMPO is divided by resistors R23, R24...R2(n+3) and as the line length is made longer and the detected voltage is increased, the TRs are turned on sequentially as TR1, TR2..., and capacitors C21, C22 are connected in the order. Thus, the resistance value and the capacitor value of the balanced connection network are decided automatically corresponding to the value of the talking current. |
