A communication terminal device (F) having an error correction function
defined in ITU-T Recommendations T.30. The communication terminal device
includes a modem (3) that can transmit data to a remote device in
accordance with a plurality of modulation methods and communication
speeds. A controller (1) associated with the terminal device (F) changes a
current modulation method of the modem (3) to a different modulation
method when an all-frame-error is detected predetermined times during data
transmission. The controller (1), however, maintains the current
modulation method and reduces a communication speed when a frame error
other than the all-frame-error is detected prescribed times.
