PURPOSE: To make effective use of a communication line, by providing an exchanger which receives a selective control signal transmitted with a called subscriber number from a calling subscriber and transmits the signal as a signal identifying the types of reception terminal for the called subscriber.

CONSTITUTION: In transfering a data to a data terminal device 2c of a called subscrber by a data terminal device 1c of a calling subscriber, when an exchanger 3 receives a prefix #9, for example as a selection control signal, a telephone set 2a of a terminal 2 is not rung, and audio frequency dial L3(941Hz)+H3(1477Hz) are transmitted as a callout signal corresponding to the prefix #9. The terminal 2 recognizes the device of itself to be called through the reception, loads the initial program and returns a response signal to the device 3 with self inspection, if normal. Thus, the data transmission/reception is made possible between the terminals 1 and 2. In case of facsimile reception, another selective control signal is used and transmission and reception of picture 1d, 2d can be made between the terminals 1 and 2 similarly.