PURPOSE: To realize bidirectional simultaneous transmission in one and the same frequency band and high-speed transmission in a narrow occupied frequency band by enhancing the ability of a transmission/reception signal separation part of a terminal.

CONSTITUTION: When a switch SW is closed, constant current is made flow to a transistor(TR) by a bridge circuit consisting of diodes D1∼D4 regardless of the polarity of telephone circuit L1 and L2. The transmission signal is sent to the circuit through amplifiers A1, A3 and A5, becomes the signal having the same phase as an inputted signal at a D point and the signal of opposite phase at an E point. Each signal at a G point and an F point have opposite phase and the same amplitude. Besides, as the phase and the amplitude of a signal at a B point is changed for voltage at an A point concerning to the signal received from the circuit, they are corrected by an impedance element Z. As the result of that, the high degree of separation can be obtained and the bidirectional simultaneous reception using the same frequency is realized.