PURPOSE: To reduce the number of cables, by providing a connector having a circuit control processor at the side of an MODEM or a data terminal and replacing the connector with two transmitting and receiving signal lines for connection to a communication controller.

CONSTITUTION: A data terminal 21 is connected to a circuit control part via connector parts 11 and 12. The part 11 contains a circuit control part 13. The data on plural signal lines 12 which are sent from the terminal 21 are controlled at the part 13 of the part 11 and stored in a memory 14 based on a command of a CPU15. These data are processed into a uniform format by the CPU15 and then transmitted to two transmitting/receiving data circuits 20 through a parallel-serial converting part 16. Thus it is possible to have a connection to a communication controller 13 by means of two signal lines and to realize an application to a system suited to an OA.