PURPOSE: To make it possible to transmit data via a coaxial cable or optical fiber cable by using a conventional code conversion part as it is, by generating a transmitted signal by exclusive OR between data shifted by a quarter of a bit and a transmitted timing pulse.

CONSTITUTION: Transmitted data, generated by the unit at the transmission side and then transferred in parallel with bits grouped at a time, are converted into series transmitted data SD by the parallel-series code conversion part. The data are shifted by a quarter of a bit at one-quarter bit shifting circuit 1 and then exclusively OR-ed with timing pulse ST used for the above-mentioned conversion to obtain transmitted signal OSD. This signal is transmitted via a coaxial cable or optical fiber cable. At the reception side, the code change point of received signal ORD is detected to find the length between adjacent code change points, so that reproducing circuit 13 will reproduce received data RD.