eli@spdcc.COM (Steve Elias) (04/12/88)
{ posted for Jay Garvin... my comments in squiggles... please post comments. }
I've seen these new boards that you can plug into your IBM-PC which
will allow you to transmit Facsimilies, but is this board really
necessary? Shouldn't you be able to transmit a fax using just your modem,
given the proper fax format and a special software program?
{ this would be nontrivial if not impossible, as far as i know.
rockwell makes the only chipset that can speak fax... }
Assuming that you *can*, I'd like to see if I could write such
software. Do you know where I can find the formats and specifications
for facsimile transmission?
For example:
* CCITT standards { someone plz post address for CCITT }
* U.S. standards
{ same as CCITT, for the most parts. some companies are using
custom methods in order to transmit greyscale images. a greyscale
method will be added by CCITT to the spec soon. }
* File storage formats for graphics and text on the IBM-PC
* Compression techniques for the data to be faxed
{ included in CCITT spec. run length & huffman codes. }
* Group III, Group IV and all that....
{ group 2 transmits entire bitmap / group 3 uses codes described
above / group 4 requires T1 medium }
I would be very grateful if you could point me to where I can find
where these specs are documented. Especially an address or phone
number for the CCITT fax specifications....
Thanks!
-Jay
+----------------------------------------------------------------------------+
| Jeffrey Jay Garvin _ |
| Computer Specialist __| | _ Aloha! |
| Interactive Services |__ |_| |__ |
| University of Hawaii ____| ____| garvin@uhccux.BITNET |
| Computing Center |__ _ |__ |
| 2565 The Mall |_| | __| garvin@uhccux.uhcc.hawaii.edu |
| Keller Hall Rm 201 |_| |
| Honolulu, HI 96822 USA |
+----------------------------------------------------------------------------+
FROM UUCP: {ihnp4,uunet,dcdwest,ucbvax}!ucsd!nosc!uhccux!garvinberger@clio.las.uiuc.edu (04/14/88)
Of course you can transmit facsimile data with any modem - but the idea
is to be compatible with real fax machines. They use an entirely different
modem standard.
Mike Berger
Department of Statistics
Science, Technology, and Society
University of Illinois
berger@clio.las.uiuc.edu
{ihnp4 | convex | pur-ee}!uiucuxc!clio!bergerhenry@utzoo.uucp (Henry Spencer) (04/15/88)
> ... Shouldn't you be able to transmit a fax using just your modem, > given the proper fax format and a special software program? Unfortunately, it's another case of "standards are great because there are so many to choose from". Computer modems and "fax modems" (so to speak) are incompatible. You could send fax data to another computer just fine, but if you want to be able to talk to fax machines, you need a "fax modem", which is essentially what the PC fax add-ons are. -- "Noalias must go. This is | Henry Spencer @ U of Toronto Zoology non-negotiable." --DMR | {allegra,ihnp4,decvax,utai}!utzoo!henry
truett@cup.portal.com (04/15/88)
There are commercial companies that sell copies of the CCITT standards but the simplest method I have found for getting them is to order them from the United Nations Bookstore in New York. The facsimile standards are in the volume containing the Series T Recommendations. The Group III encodings are in T.4 and the Group IV codings are in T.5. The comment made by someone that Group IV requires T1 transmission is wrong. The group I and II standards assumed an analog transmission method. Group III facsimile uses a digital method but incorporates error recovery features. Group IV contains no error recovery features since it assumes a separate Link Layer is handling that chore. As for the differences between "fax" modems and "data" modems: A fax modem establishes a connection using V.25 signalling and an information exchange protocol with the other end (defined in T.30) that is conducted at 300 bps. It then switches to the highest speed the other end says it can accept, which is usually either 4800, 7200, or 9600 bps. This is a half-duplex, synchronous data transfer conducted using V.29 signaling. A data modem, however, establishes the connection using a V.21 sequence of training tones which the originating modem responds to to let the answering modem know it has agreed on a frequency. This is quite different from the use of a fixed 300 bps starting speed to exchange data about available higher rates. Most 9600 bps data modems are either using V.29 half-duplex or V.32 full-duplex. There are also modems which use the 14.4 kbps V.33 standard but run it at 9600 which it allows as a fallback. Note that all 9600 modes are synchronous. Finally, the ANSI standards can all be acquired from CBEMA in Washington, D.C. Truett Lee Smith, Sunnyvale, CA UUCP: truett@cup.portal.com
gnu@hoptoad.uucp (John Gilmore) (04/16/88)
henry@utzoo.uucp (Henry Spencer) wrote:
> ...if you want to be able to talk to fax machines, you need a "fax modem",
Note that a "fax modem" is just a 9600 baud half duplex modem, sort
of like the 1200 baud Bell 202 modems of years gone by. I looked at
these a few years ago (a friend sells an IBM PC card with this chip set)
but it takes it most of a second to turn the line around, so it's really
pretty useless for interactive use. Or even for file transfers, if you
need flow control or error retransmission.