Fax Standards - Group 1, 2, 3, and 4

Fax standards have emerged from analog transmission units (Group 1,2) in the late sixties and early seventies to the digital transmission units (Group 3,4) in the eighties. The Group 3 facsimile standard however, has been in wide use for two decades now. The salient points about these standards are summarized below.

• Group 1
  • Became a standard in 1968 for analog facsimile devices to communicate over analog telephone lines.
  • Unreliable, six minutes per page, poor resolution.
  • The characteristics and operation of the facsimile devices conforms to the ITU-T Recommendation T.2.

• Group 2
  • Became a standard in 1976 for analog facsimile devices to communicate over analog telephone lines.
  • Worldwide compatibility.
  • Three minutes per page.
  • The characteristics and operation of the facsimile devices conforms to the ITU-T Recommendations T.30 and T.3.

• Group 3
  • Became a standard in 1980 for digital facsimile devices to communicate over analog telephone lines.
  • Provides flexibility to add innovative features without compromising basic compatibility with standard Group 3 machines.
  • 6 to 30 seconds per page, plus about 15 seconds for the first page initial handshake.
  • The characteristics and operation of the facsimile devices conforms to the ITU-T Recommendations T.30 and T.4 [ITU96b].
  • It is the current standard.

• Group 4
  • Became a standard in 1984 for digital facsimile devices to communicate over digital telephone lines.
  • Designed for ISDN 64 kbps.
  • The characteristics and operation of the facsimile devices conforms to the ITU-T Recommendations T.563, T.503, T.521, T.6, T.62, T.70, T.72, T.411 to T.417.
  • Incompatible with Group 3.