Internet fax machines. This has limited the standard's use, though a system for looking up a fax's email address based on its phone number is under development. To work with existing fax machines, all iFax machines support standard faxing (requiring a regular phone line). Alternatively, an iFax can be used in conjunction with a fax gateway. Internet fax Internet fax, e-fax, or online fax is the use of the internet and internet protocols to send a fax (facsimile), rather than using a standard telephone connection and a fax machine. A distinguishing feature of Internet fax, compared to other Internet communications such as
Fax to the e-mail to fax service that still uses fax modems at least one way. Computer modems are often designated by a particular fax class, which indicates how much processing is offloaded from the computer's CPU to the fax modem. Several different telephone line modulation techniques are used by fax machines. They are negotiated during the fax-modem handshake, and the fax devices will use the highest data rate that both fax devices support, usually a minimum of 14.4 kbit/s for Group 3 fax. Note that "Super Group 3" faxes use V.34bis modulation that allows a data rate of up to