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Chapter 6 Principle of Operation (Fax)
Version 1 2006.11.21
Printer
The printer prints image data from the control circuit onto the surface of paper. The principle is the
same as that of an ordinary printer in that black is applied to specified locations on the paper.
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
Transmission
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
technology
Group 2 (G2) 1976 Approx. 3 min. 100 x 100dpi
-
(Analog)
Analog transmission.
Band compression
technology adopted.
Group 3 (G3) 1980 Approx. 1 min. 200 x 200dpi
14.4kbps
(Super G3:
33.6kbps)
Connection to analog line
using FAX modem.
Image data in digital
format.
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
digital transmission
services.
Halftone supported.
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