PURPOSE: To transmit data while adding a binary signal without changing encoder/decoder by transmitting a digital signal inverted/non-inverted depending on an added signal and allowing the reception side to discriminate the inversion/ non-inversion to read the value of the added signal.

CONSTITUTION: On/off signals of remote control switch are given to terminals a1∼an, an+1, and an encoder 2 and outputs a serial code signal as shown in the figure A. The said signal is non-inverted/inverted by a buffer circuit 11 and an inverter circuit 12 respectively and the result is inputted to switch 10, which uses an added signal given to the terminal an+1 as a control input to transmit the said inverting/non-inverting signal in response to the ON/OFF of the said signal. The said signal is fed to a reception circuit 5 and a discrimination circuit 13. The discrimination circuit 13 integrates the input signal and applies the integration value (broken lines I) of the non-inverting signal and the integration value (broken lines II) of the inverting signal to the inverter circuit 14. The circuit 14 has a threshold value larger than the broken lines II and smaller than the broken lines I, then the added signal is reproduced and outputted from a terminal bn+1.