A facsimile use modem apparatus includes an analog interface formed from a silicon data access arrangement interfacing with an analog telephone line. A digital interface is provided to interface with an ISDN line. A signal converting device is provided to convert a modem signal used in facsimile communications via the analog telephone line into a signal used in the ISDN line, vice a versa. A data transmitting device is provided to transmit linear data to a monitor via the silicon data access arrangement when G3 facsimile communications are performed via the ISDN line so as to monitor a progress of the G3 facsimile communications.