PURPOSE: To select the code converter of a receiver directly from a transmitter by receiving code converter selection data added to data transmitted from the transmitter and selecting the code converter.

CONSTITUTION: A start detector 10 decodes sent data, sends a start detection signal S to a prefix register 9, and holds prefix data sent for the 1st time after the start detection signal S is inputted. A decoder 8 decodes the prefix data and outputs control signals (a) and (b) for selecting code converters A4 and B5. A command data unit whose prefix data is 00 and an image data unit whose prefix data is 10 are is outputted to a data bus 6 without being altered by selecting the code converter A4. An image data unit whose prefix data is 11 as a result of black and white inversion is passed through the code converter B5 to invert respective bits of the code, and outputted to the data bus 6.