Abstract: When a data communication apparatus as a sender gateway receives instruction information for instructing a communication system via ITU recommendation T.38 or a communication system via ITU recommendation T.37 from a sender facsimile apparatus as an analogue communication terminal, data communication is executed with respect to a recipient connected gateway on the basis of the communication system instructed by the instruction information.

Abstract: A communication terminal having an interface to which its components including an analog telephone are connected and which enables communication with another terminal at the other end of a line of the integrated services digital network. A first tone is generated to set the period of time for dialing of the analog telephone, a second tone different from the first tone is generated to set the period of time for connection between the analog telephone and the terminal at the other according to the dialing during the period of time when the first tone is being generated, and a third tone different from the first and second tones is generated to set the period of time for terminating communication using the analog telephone when the connection established during the period of time when the second tone is being generated is cancelled. Each of first, second and third tones generated is output to the analog telephone.