| 摘要 |
PURPOSE:To make the impedance in the extension side equal regardless of any connection path, by connecting an impedance compensation line to the connection path between the extensions and a main trunk. CONSTITUTION:A telephone set N and a main trunk CO are connected via a channel SW of a normal private branch of exchange and a main line trunk COT, and the smoothing circuit network Zn of this telephone set N is designed in matching to the impedance Zp at the extension side of the private branch of exchange. When the telephone set N is used at night as a direct call telephone set, a switching relay (not shown) is operated and the telephone set N is connected to the main trunk CO via the make-side between the CO and contacts nt<0>-nt<3> and impedance compensation circuit BN. The compensation of impedance viewing the CO from the telephone set N is made at the compensation circuit BN to reduce the side tone when the telephone N is used as direct telephone set. |
