PURPOSE: To avoid a trouble till data communication is started by selecting the on-line job with a different communication mode by means of the menu selection system and setting a relevant communication mode.

CONSTITUTION: A communication mode corresponding to the on-line job to be selected by a menu selection means 2 is set on a communication mode relevant table 3. In this case, plural communication modes are considered to one on-line job. When plural communication modes corresponding to one on-line job exist, a communication mode selection means 4 uses a keyboard 8 to enter the communication mode to be used among the communication modes set on the communication mode relevant table 3 to select the desired communication mode. Then a communication mode notice means 6 informs the selected communication mode from a computer to a MODEM built-in telephone set 9. Thus, the operation is facilitated.