PURPOSE: To make it possible to regenerate stably a data signal without being influenced by various charcteristics of a communication medium and external mixing noises, by using a processed reference clock signal under fixed conditions.

CONSTITUTION: For transmission or recording, a string of pulses is generated 31∼ 35 which is obtained by inverting the phase of a basic clock signal applied to terminal C in accordance with a PCM data signal applied to terminal D on the basis of the clock signal, and this string of pulses is added 37 to the PCM data signal with fixed amplitude. In reception or reproduction, on the other hand, a lower signal is polarity-inverted 39 on basis 41 of a level a half the amplitude of a obtained signal and then added 42 to an upper signal to reproduce a reference clock pulse. Then, this reference clock pulse is supplied to latch circuit 313 for the PCM data signal, and consequently stable data regeneration can be attained.