PURPOSE: To reduce a load of a central processing system and to obtain a high responsiveness of an echo by inputting an echo command signal inputted from the central processing system, to a communication control device, and echoing it in the communication control device.

CONSTITUTION: When a character data inputted from a terminal device 8 is inputted to an input control device 1, and subsequently, inputted to an echo control device 4, an echo mode latch 7 is checked with respect to the character data, and if the check is on, said data is outputted to a message assembling buffer 6, and also the data is inputted to the terminal device 8 through an output control device 2. If the check is off, the data is stored in a preceding input buffer 5. A data transfer interface device 3 turns on the echo mode latch 7 in accordance with an echo command signal inputted from a central processing system 9, and informs it to the echo control device 4, therefore, the character data stored in the preceding input buffer 5 is outputted to the message assembling buffer 6, and also sent out to the terminal device 8.