PURPOSE: To improve the processing capability by using a bit arrangement converter to convert bit arrangement in a byte data in transmitting the data received by a serial parallel converter via a parallel serial converter.

CONSTITUTION: A bit arrangement converter 6 is added to a conventional device consisting of a serial/parallel converter (S/P) 3, a parallel/serial converter (P/S) 4 and a demodulator-modulator (MODEM) 5 by using a microprocessor (MPU) 1 and a main storage device (MM) 2 as center devices. The data received by the S/P 3 is edited and given to the P/S 4 as a transmitted data. In this case, the form of transmission signals for reception and trasmission is different and it is required to conduct processing rearranging bits in the byte data, then the bit arrangement converter 6 is used without using a program and the rearrangement of bit arrangement is attained by the write and read processing only to the converter thereby improving the processing capability.