PURPOSE: To recover communication fault quickly by improving the C/N characteristic in an incoming direction so that the occurrence of the communication fault due to noise does not give adverse effect onto the entire system.

CONSTITUTION: Part of an incoming signal is extracted from an incoming line of a two-way amplifier 1 of a two-way CATV as a monitor signal, and when the monitor signal is consecutive for a predetermined time or over, it is judged that undesired noise is invaded to allow a status monitor circuit 2 of the two- way amplifier 1 to provide a control signal thereby turning off a switch 3 of the incoming line of the two-way amplifier 1. When undesired noise is invaded in the monitor signal, a notice signal to notice noise invasion is sent from the status monitor circuit 2 of the two-ray amplifier 1 to a center.