To enable terminals which use different communication protocols to communicate data and voice at the same time by separating speech packets and data packets, reconstituting the voice data in real time, and then transmitting them over different channels.

When a data terminal 606 of a LAN 604 makes a dial-in connection, the access point 605 sends a request to communicate data and voice to a gateway 602 with a radio frame. The gateway 602 connects a link through ISDN 601. When the voice is inputted to the data terminal 606 through the handset, the data terminal 606 adds media kind information 'voice=10' PCM- converted data and sends them to a frame assembly part. When a file is inputted from a data input/output interface in parallel, media kind information 'data=01' is added and sent to the frame assembly part. The gateway 602 discriminates between the frames of the data and voice and send them to the B1 and B2 channels of ISDN respectively.