PURPOSE: To perform communication with one line even between stations with different system clocks by transmitting a long pulse signal and a short pulse signal to a data bus wire following after a reference pulse signal.

CONSTITUTION: The communication with one line can be performed even between the stations with different system clocks by expressing a data bit system as size relation between the pulse width of arbitrary times that of the reference pulse signal and the pulse width of a pulse signal representing a data bit. Data can be surely communicated by performing reception by setting the pulse width of the long pulse signal outputted from a transmission station 1 longer by arbitrary times than that of the reference pulse signal, and the pulse width of the short pulse signal shorter by the arbitrary times than that of the reference pulse signal, and performing reception by reception stations 3, 4 setting the pulse signal longer by arbitrary times than the pulse width of the reference pulse signal as '1', and the pulse signal shorter by arbitrary times than the pulse width of the reference pulse signal as '0' and providing difference in the pulse width.