To demodulate a different modulation format without increasing the number of demodulators and modulators by receiving a modulated coming signal by one of plural modulation formats and determining a modulation format of the received coming signal by processing the received coming signal.
Communication is performed between two devices to commonly use a multipurpose modem, modulation types can be switched according to detection of degradation of a communicating state. This switch of the modulation types is executed by using a channel noise detector 258 to be connected with a controller 208 to detect a noise on a channel. A proper modulation format, frequency, band width are specified and communication with higher reliability is realized by the channel by the controller 208. When modulation types are predetermined by every channel between a transmitter and a receiver, a modulation type of the multipurpose modem 204 or 206 is controlled on both sides of the transmitter and the receiver by a controller such as the controller 208. A modulation request signal is inputted in an information source encoding part 226 by the multipurpose modem 204 on the transmitting side.
BAO JAY
MIZUTANI YOSHIKI
NAKAYAMA HIROYUKI
