CCITT Group 4 classification is not a format, but rather a classification of
facsimile machines for document transmission over the public networks. Groups
1, 2, and 3 are for use over the public telephone network. Group 4 is for use
over the public data networks, which also may include the public telephone
network. In other words, Group 4 does everything the other groups do, plus
more. It specifically incorporates means for reducing the redundant
information in the document prior to transmission and assuring essentially
error-free reception of the document.
It is important to understand that CCITT Group 4 is not a format. It is many
pages of specifications that explain exactly how an apparatus of this grouping
works. It specifies the binary description of the document.
As of August, 1989, Tech Comm did not know of any application or utility for
the Macintosh that is CCITT Group 4-compatible.