Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request
From: hrs1@cbnewsi.ATT.COM (herman.r.silbiger)
Newsgroups: comp.dcom.telecom
Subject: Re: Fax Group IV
Message-ID: <3724@accuvax.nwu.edu>
Date: 10 Feb 90 17:32:41 GMT
Sender: news@accuvax.nwu.edu
Organization: AT&T Bell Laboratories
Lines: 56
Approved: Telecom@eecs.nwu.edu
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@eecs.nwu.edu
X-Telecom-Digest: Volume 10, Issue 90, message 5 of 9


Regrading the request for information on Group 4 fax standards, I will
list them below:

There are actually three types of G4 machines defined, Classes I, II,
and III.

Class I transmits on a line by line basis, has a standard resolution
of 200x200 pels/inch (optional: 240x240, 300x300, 400x400).

Class III transmits on a page basis, has a standard resolution of
300x300, the others optional, and has mixed-mode as a standard, i.e..
it can transmit and receive pages with character coded and raster
graphics coded information intermixed on the same page.

Class II is like class III, but can only receive mixed-mode, not send
it.

Class I machines cannot directly interwork with class II and III
machines, since they use different protocol stacks.

G4 machines also cannot directly interwork with G3 machines, although
many current machines have G3 capability included as a separate board.

G4 Recommendations:

T.412  Document Structures
T.415  Open Document Interchange Format
T.417  Raster Graphics Content Architectures
T.431  Document Transfer and Manipulation - Service Definition
T.432  Document Transfer and Manipulation - Protocol Specification
T.501  Document Application Profile for the Interchange of Formatted Mixed
	Mode Documents (for Class II and III)
T.503  Document Application Profile for the Interchange of Group 4 Facsimile
	Documents (for Class I)
T.521  Communication Application Profile BT0 for Document Bulk Transfer Using
	the Session Service Defined in Rec. T.62bis (for Class I)
T.522  Communication Application Profile BT1 for Document Bulk Transfer (for
	Class II and III, uses session service defined in X.225)
T.561  Terminal Characteristics for Mixed Mode of Operation MM (for Cl II & 
        III)
T.563  Terminal Characteristics for Group 4 Facsimile Apparatus

Image coding for G4 follows Rec. T.6.

Work is currently under study in CCITT for enhancing Group 3 to add
higher resolutions (to 400x400), T.6 encoding, and an ISDN interface,
while maintaing full compatibility with existing G3 equipment.
Currently, only G4 is available with a 64 Kb/s interface.

Equipment conforming to ODA profiles level 2 and 3 also have the
capability of sending raster graphics image pages.


Herman Silbiger