| 摘要 |
PURPOSE:To reduce the influence of disturbance due to an impulse noise, etc., by comparing a transmitting line input level with a receiving live input level, and executing an operation of a temporary interruption and a full interruption by the time limit of its output. CONSTITUTION:A part of a receiving signal outputted from an output terminal 2 is reflected by mismatching of the impedance, leaks to the transmitting side, reaches an input terminal 3 of the transmitting line, and becomes an echo. When it has been decided by a suppression threshold level detecting circuit 7 that a receiving line input exists, in case when a transmitting line input does not attain to an interruption threshold level by an interruption threshold level detecting circuit 9, a suppression loss circuit 6 is inserted, and when it is detected by the interruption threshold level detecting circuit 9 that the transmitting line input has exceeded the interruption threshold level, a receiving loss circuit 5 is inserted, the receiving signal is also attenuated, and an echo becomes small. In this way an operation of a temporary interruption and a full interruption is executed by the ltime imit of an output of the interruption threshold level. |
