| 摘要 |
PURPOSE:To prevent the deterioration in the side tone characteristic at power failure and to ensure excellent communication quality, by providing a network matched to the impedance condition of a communication circuit and switching the network with a changeover switch. CONSTITUTION:A balance network 108 for power failure is provided in addition to a balance network 107 for power application. The changeover switch 106 is provided to the network 108 so as to changeover the state of power application and failure. Further, the network 107 is a circuit matched to a line impedance 101 including a channel impdedance 102 and a channel 109, and the newtowk 108 is a circuit matched directly to the line impedance 101. |
