A communication terminal device connected to a communication network via a plurality of information channels used for transfer of information such as line switching information or packet switching information and a signal channel used for control of calling an objective communication terminal. In the device, two CODECs are provided in two corresponding information channels among information channels and analog sources such as a handset and a communication function control unit operative in a G3 facsimile mode for encoding and converting switching information, supplied from the analog sources to the information channels, to a digital signal, and decoding and converting switching information received from the information channels, to analog signals. Analog switches are provided between the analog sources and the CODECs to switch among the analog switches and these CODECs to send and receive signals to and from the analog sources and the CODECs. Thus, simultaneous communication of image information (G3 mode)/image information (G4 mode), image information (G3 mode)/voice information, and voice information/voice information is possible depending on the aspect in which the analog switches are switched.