Abstract: In a case where a signal from a G3FAX terminal is transmitted through an ATM network, the fact that the media is a G3FAX terminal is recognized in a tone detecting section or FAX protocol control section within an ATM exchanger and the data is digitized in and transmitted from the FAX processing section, but in this step a congestion level is identified by a congestion state detecting section according to the traffic data measured in the traffic measuring section as well as in the ATM bus control section and other device congestion data in the network, a transmission rate for G3FAX signal transmission is decided according to a congestion level in the FAX speed control section, and the connection protocol between G3FAX terminals is controlled by the FAX protocol control section to transmit the FAX signals controlling a transmission rate between G3FAX terminals.

Abstract: A multiplexer adds synchronizing bits to receive data transmitted from a digital communication line to a digital private branch exchange, and checks for synchronizing bits in send data transmitted from the digital private branch exchange to the digital communication line. If the multiplexer detects synchronizing bits, it switches to a non-compression mode in which it transmits selected bits of send data without compression, and transmits receive data without decompression but with addition of synchronizing bits.