Group 3 <protocol, compression> (G3) The {CCITT} fax {protocol} which uses data {compression} and allows a variety of file types (e.g. {electronic mail}, pictures, {PostScript}) to be transmitted over {analogue} telephone lines. The Group 3 protocol was published by {CCITT} in 1993. Full details of the protocol are available from {ITU-T}. See also {Group 4}. (1998-10-03)