PURPOSE: To revise a real time of a transmission signal and to select the revision of a transmission speed optionally by applying phase control to a sent serial data in the unit of bits.

CONSTITUTION: A phase control transmission section 8 sends a serial data signal and an interrupt marker signal resulting from varying a bit width of a serial data and an interrupt marker data read from a memory 6 in the unit of bits corresponding to the quantity of pulse number of clocks from a clock section 13 designated by a phase control data read from the memory 6. Thus, the signal transmission speed is selected optionally during the transmission of the serial data signal and the interrupt marker signal is given to the data source to revise the format of the serial data stored in the memory 6 in real time.