Communication system using a modem with a mode in which data receiving operation is shifted to control signal communication upon detecting a momentary disconnection

Abstract

Even if a signal line is momentarily disconnected while data communication, such as image data communication, is being performed by using, for example, an ITU-T Recommendation V.34 modem, communication is suitably continued. A main controller (CPU) determines the operating state (status) of a modem having the following mode. In this mode, the receiving operation of an image signal is automatically shifted to control signal communication upon detecting a pattern of a training signal. The main controller enables the above mode if it determines that the receiving status of the modem is not normal. It is thus possible for the modem to shift from the receiving of an image signal to control signal communication when the signal line is momentarily disconnected.

Dependencies are inferred from the claim text.