PURPOSE: To connect also a data terminal device not transmitting a dial signal identical to that of a telephone set as the terminal device of an exchange by providing a means receiving a character signal train and converting it into a numeric signal train to the exchange.

CONSTITUTION: A CPU60 is connected to a channel switch circuit 50 and a station data storage circuit 70 storing information such as a telephone number required for exchange processing. The output of the circuit 50 and the CPU60 is inputted to a data terminal controller 30 and a terminal controller 40, data terminal devices 11∼13 are connected to the controller 30 and telephone sets 21, 22 and a data terminal device 14 are connected to the controller 40 respectively. A corresponding list between the data terminal name and the telephone number of the data terminal device is stored in the circuit 70. In communication data from, e.g., the terminal device 11 to the terminal device 13, when a terminal device name CC of the terminal device 13 is in the form of a character signal, the controller 30 transfers it to the CPU60 as it is. The CPU60 reads the telephone number from the terminal device name stored in the circuit 70 and commands the connection between the terminal devices 11 and 13 to the circuit 50 and the controller 30.