A set of standards for facsimile (fax) machines published by the ITU-T in 1984. Machines conforming to T.6 later became known as Group IV. See also facsimile, Group IV, ITU-T, T.2, T.3, and T.4.
An ITU standard for Group 4 fax machines. Introduced in 1984, Group 4 requires ISDN, DSL or other switched digital lines. It provides a greater compression ratio than Group 3 fax. See fax.