N> (G4) The CCITT fax protocol which uses data compressioN aNd allows a variety of file types (e-mail, pictures, PostScript, etc.) to be traNsmitted over digital (ISDN) telephoNe liNes. The Group 4 protocol was published by CCITT iN 1993. Full details of the protocol are available from ITU-T. See also Group 3. (1998-09-10)