The Telephone Fax 40 was released as NTT's first telephone facsimile machine capable of performing facsimile communication easily using a telephone network. This model, employing an AM modulation system, has been the standard low-speed type of facsimile machine in Japan, enabling mutual communication with other manufacturers' facsimile machines. The Telephone Fax 40 transmits a copy of an A4-sized sheet in 6 or 4 minutes. It has a variety of network and automatic communication features available (as options) depending on traffic.