To attain multiple use of media by using different frames for voice data and computer data and distinguishing both data based on frame sequence.

In the case of multiplex communication, when a ratio of computer data in a non real time system to voice data in a real time system is set to 1:0, that is in agreement by both terminal equipments, the computer data stored in a buffer 14 are transferred sequentially in the unit of transmission frames by a communication IF 19. When the agreement ratio is 1:1, the computer data stored in the buffer 14 are transferred sequentially in the unit of transmission frames by a communication IF 19 and voice data stored in a bus connection IF 13 are sent via a transmission buffer 18 sequentially. In this case, a voice encoder 11 encodes the voice data at a 1/2 transmission rate and coded data by one transmission frame are stored in the IF 13 in a voice data transmission timing and a buffer full notice is informed to a multiplex transmission control section 17 in this timing. After the control section 17 transfers the voice data stored in the IF 13 to the buffer 18, the data are sent by a transmission interrupt from the IF 19.