A microprocessor unit of a communication terminal device determines
whether or not a destination terminal is a communication terminal
manufactured by a same manufacturer as the communication terminal device
in accordance with a manufacturer code transmitted from the destination
terminal. A display unit displays a message to notify a determination
result to a transmitter and to urge the transmitter to perform a
selection operation for executing or canceling a transmission of image
data. When the transmitter selects a function key displayed on the
display unit in accordance with the message, the microprocessor unit
executes or cancels the transmission of the image data.