PURPOSE: To eliminate the distortions of an output waveform caused at the start of transmission by delaying an inhibiting signal and using this delayed signal (delayed transmission state signal) to change a driven control signal.

CONSTITUTION: An inhibiting signal (c) is delayed by an extent equal to a time difference Δt via a delay circuit 2 and outputted as a delayed transmission state signal (f). The waveform of a 1st digital output signal (d) or a 2nd digital output signal (e) is deleted by the signal (f) by an extent equal to the first Δt at the start of transmission and outputted as a 1st driver control signal (g) or a 2nd driver control signal (h). As a result, a biphase differential output signal (k) is also deleted by its first Δt at the time of transmission. In such a way, the distortions of an output waveform can be eliminated at the start of a broadcast.