To attain sufficient wiring saving and power saving by generating out a multiplexed serial signal by adjusting a serial data signal and a control signal so that the peak value of each signal waveform can become a prescribed ratio to output it, and detecting only the part exceeding the prescribed peak value among the signal waveforms of received multiplexed serial signals.

A transmitter 11 converts plural input data signals inputted as parallel data signals to serial data signals. Further, the multiplexed serial signals, by adjusting, overlapping and multiplexing the serial data signal, clock signal and load signal so that the peak value of the waveform can become the prescribed ratio, are generated and transmitted through a multiplex signal line 14. When a receiver 12 receives the multiplexed serial signal, only the part exceeding the prescribed peak value in the signal waveform of the multiplexed serial signal is detected, demultiplexed into the serial data signal, clock signal and load signal, further returned to the original input data and outputted.