Group II - technical definition

A set of standards for facsimile (fax) machines published by the ITU-T in 1978 as T.3. Group II specifies black-and-white mode of operation and compression through the use of encoding and vestigial sideband (VSB) transmission. Group II machines use amplitude modulation (AM) and phase modulation (PM) at a carrier frequency of 2100 Hz. Group II machines use compression to improve transmission speed to approximately two-three minutes per page, but resolution is relatively poor at 100 lines per inch (lpi). Group II machines use the same obsolete electrochemical printing process as Group I machines and are, themselves, considered obsolete. See also AM, carrier, compression, facsimile, Group I, ITU-T, PM, resolution, and VSB.