To correct a phase of a voice signal without manual operation.

Phase detection signals R, S are superimposed on the same voice program signals P, Q sent from transmission stations 1, 2 and the same phase is provided to the voice program signal P and the phase detection signal R and a phase difference of 180° is set to the voice program signal Q and the phase detection signal S. A demodulation section 13 of a reception section 3 demodulates only the phase detection signals R, S and a comparator section 14 compares both the voltages and outputs the sum of the both as a comparison result. An arithmetic section 15 conducts arithmetic operation to make the sum voltage zero and outputs the result to a phase control section 16. The phase control section 16 corrects the phase of a phase shifter 7 of the transmission station 2 based on the result. As a result, the phase difference of the phase detection signals R, S is 180° and the voice program signals P, Q are set to be the same phase.