PURPOSE: To reduce the number of lines between a repeater and a terminal equipment by absorbing a difference between a non-protocol and a transmission control protocol other than the non-protocol.

CONSTITUTION: An integrated transmission control section (non-protocol transmission control section 1 and X modem protocol transmission control section 2) uses the non-protocol transmission control section 1 to implement transmission reception of data with a non-protocol terminal equipment 20 and transmission/ reception of data with a terminal equipment (X modem protocol terminal equipment 30) adopting a transmission control protocol other than the non-protocol in common, decides the transmission control protocol based on whether or not discrimination object data corresponds to a specific character string and implements the control of transmission of data by non-protocol and control of transmission of data by the transmission control protocol relating to the specific character string through the same line. A code conversion section 4 and an edition section 5 implement code conversion and adjust data form for data of the transmission object so as to be in matching with the transmission control protocol decided by the integrated transmission control section.