Abstract: A method for switching a modem in a key telephone with a single communication line, wherein modem connection circuit is provided so as to use the single communication line as both a speech and a data path. Data communication is performed by using the single communication line without an extra data communication line.

Abstract: A videophone includes an interface that enables communication between a videophone and another type of device, such as a speech-only telephone. In one embodiment, a signal processing circuit processes video and another type of information, respectively, in parallel data paths and operates in either a non-video mode or a video mode in response to whether or not another communicatively-coupled terminal represents that it is not operable as a compatible videophone. A two-way converter circuit coupled between the signal processing circuit and the communication channel transceives the video and the other type of information as processed in the parallel data paths with the signal processing circuit, and transceives the video and the other type of information with the communication channel.