| 摘要 |
PURPOSE:To ensure the conference telephone service over a wide region by providing the echo canceller between the amplifier and the hybric coil of the conference trunk which performs the talking level compensation in order to secure setting of the amplifier gain to the optional value. CONSTITUTION:The conference trunk circuit contains plural talking terminals 0- n which are connected to talking level compensating amplifier circuit AMP via hybrid circuit H. Then, echo canceller circuit EC is connected between each hybrid circuit H and circuit AMP. Thus, the ringing caused by the talk detouring due to the unbalanced component of circuit H is prevented, and the gain of circuit AMP can be set to an optional value. As a result, the conference telephone service can be extended up to the toll region. |
