PURPOSE: To speed up the data communication by constituting a combination means between a telephone set and a terminal equipment through the provision of a changeover device having an external connection terminal to a telephone set main body or connecting the means to the terminal device through the provision of a changeover device to a cord of the telephone set.
CONSTITUTION: A switch 12 changing the path of an electric signal and a changeover device having the external connection terminal 11 are provided. When the terminal device 13 is not connected to the telephone set 4, the switch 12 is closed at all times and then a roset 2 and the telephone set circuit 6 are coupled directly to attain conventional talking. When the terminal device 13 is connected to the telephone set 4, the switch 12 is closed, the roset 2 and the terminal device 13 are coupled directly and the telephone set circuit 6 is connected to the roset 2 via the terminal device 13. Thus, the transmission/ reception electric signal of data communication is not converted into an acoustic signal as conventionally but transmitted/received with an electric communication line L as it is.