PURPOSE: To transmit a coded mark inversion code (CMI code) by use of a device for transmitting a bipolar code, by converting the CMI code to the bipolar code.

CONSTITUTION: A received CMI code arrives in a terminal 1. A delaying circuit 2 has a delay time of 1/2 of a bit period of the CMI code. To an AND circuit 3 and an OR circuit 4, the CMI code and an output of the circuit 2 are applied. Outputs of the circuits 3, 4 are applied to differentiating circuits 5, 6, clipping circuits 7, 8 and a monostable multivibrator 9. A delaying circuit 11 adjusts phase by delaying a pulse (h) by 1/2 time of the bit period. The circuit 11 and an output of an inverter 12 are added by an adder 13, and a bipolar code (k) is obtained.