10 – 16
Chapter 10 Machine Overview
10.6 FAX Standards (ITU-T Recommendations)
International FAX standards (ITU-T recommendations) include G1 to G4. G1 to G3 use analog
telephone networks. G4 uses a digital telephone network (ISDN). G3 is the standard currently in
greatest use. FAXes conforming to Super G3, a recently added standard, are equipped with a fast
33.6kps modem and reduce transmission times to about half those of G3 FAXes.
Standard Year Issued
Minimum Trans-
mission Time for
Single-Page A4
Document
Maximum
Resolution
Maximum
Transmission
Speed
Features
Group 1 (G1) 1968 Approx. 6 min. 100 x 100dpi
-
(Analog)
First standard.
Analog transmission.
No band compression tech-
nology
Group 2 (G2) 1976 Approx. 3 min. 100 x 100dpi
-
(Analog)
Analog transmission.
Band compression technol-
ogy adopted.
Group 3 (G3) 1980
Approx. 1 min
(14.4kbps)
Approx. 3 sec
(33.6kbps)
600 x 600dpi
14.4kbps
(Super G3:
33.6kbps)
Connection to analog line
using FAX modem.
Image data in digital for-
mat.
Data compression.
Most common standard in
use.
Group 4 (G4) 1988 Approx. 3 sec. 400 x 400dpi
64kbps
(Using ISDN)
Digital transmission.
Supported by various digi-
tal transmission services.
Halftone supported.
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