| 摘要 |
PROBLEM TO BE SOLVED: To increase impedance in a frequency band of a sound signal to be controlled to become high impedance, in order to facilitate superposition of a voice signal on a transmission line when the voice signal is superposed on a power supply to be supplied to the transmission line during the speech with a slave unit.SOLUTION: An amplification function of a noninverting amplifier circuit which outputs reference voltage V1 to be generated by a reference voltage generation circuit 23 for operating a master unit and a slave unit to the transmission line is executed by applying a master unit transmission voice signal to be transmitted from a master unit microphone 20 via a master unit hybrid circuit 22 of the master unit 2, and a slave unit transmission voice signal to be transmitted from a slave unit microphone 10 via the transmission line L1, a slave unit hybrid circuit 12 of the slave unit 1 sequentially to a noninverting input terminal of an amplifier OP of a noninverting amplifier circuit 25 via a capacitor 26 and making a resistance value of a resistor 27 on appearance viewed from the master unit microphone high. |
