PURPOSE: To improve the substantial transmission speed by increasing an information quantity per one bit.

CONSTITUTION: Devices A, B are digital devices processing a binary signal such as a computer system and they are provided respectively with major sections 1A, 1B executing its major operation and binary/n-ary converters 2A, 2B and the data is transferred between the devices A, B via a data bus 3. The binary/n-ary converters 2A, 2B convert a binary signal outputted from the major sections 1A, 1B, that is, a digital signal into an n-value signal respectively and it is outputted to a bus 3 and the binary/n-ary converters 2A, 2B convert the n-ary signal sent through the bus 3 into a binary signal and it is sent to the major sections 1A, 1B.