PURPOSE: To avoid an unnatural black point component from being introduced in a reproducing signal by generating a signal indicating a phase change when a picture signal to be transmitted exceeds a predetermined amount of change above a signal giving a prescribed time of delay to said picture signal.

CONSTITUTION: The picture signal given to a transfer line 1 is applied to a delay circuit 2 delaying the signal by a predetermined time, e.g., one picture element's share and also fed to a comparator circuit 3. The comparator circuit 3 discriminates whether or not the value of the picture information signal on the transfer line 1 exceeds a predetermined amount of change above the value of an output signal of the delay circuit 2 and when the value exceeds the amount of change, a phase control signal representing the indication of the phase change is generated. This phase control signal is fed via a signal line 6 to an MODEM4, where the picture information signal fed from a transfer line 5 is phase-controlled and AM-PM-VSB modulation is applied to the picture information signal.