PURPOSE: To improve the utilizing efficiency of a 4-wire system exclusive line by connecting the 4-wire exclusive line to an external device by switching in response to a control signal.

CONSTITUTION: A semi-duplex communication facsimile terminal is provided with a switching controller SW-CONT which is connected optionally by switching to an external device DTE such as data terminal by an output signal of a controller CONT incorporating transmission/receiving terminals of 4-wire exclusive lines 4WS, 4WR. Further, an storage exchange connects optionally by switching the lines 4WS, 4WR to the device DTE via the similar device SW-CONT. When the unidirectional or bidirection transmission line of the lines 4WS, 4WR is idle, the idle transmission line is used for the information transmission between the devices DTE. As a result, the utilizing efficiency of the lines 4WS, 4WR is improved.