PURPOSE: To attain simple level adjustment of a relay amplifier by performing the setting of a line length equalizer circuit with a control signal from the center.

CONSTITUTION: A two-way relay amplifier is provided with input/output level detecting circuits 3, 4, its level transfer circuit 6 and variable line length equalizing circuits 1, 2 and also a receiver 7 receiving a control signal transmitted from the center. An output of the receiver 7 is fed to a control circuit 5, which controls the level transfer circuit 6 and the variable type line length equalizing circuits 1, 2 based on the control input. That is, when an instruction signal of level transfer is transmitted from the center, the transfer circuit 6 is operated and when a setting signal of the equalizing circuit is transmitted, the control circuit 5 is operated and the equalizing circuit 1 is set to a designated value. Then the level signal after setting is transferred to the center.