- ANSI/AIIM MS53-1993
- The American National Standard File Format for Storage and Exchange of
Images - Bi-Level Image File Format: Part 1 (ANSI/AIIM MS53-1993) was
approved in 1993. The standard defines a format for a file containing
one page with one image. Page sizes and image sizes can be specified.
Both definite length and indefinite length are supported. Clipping of the
image can be specified. Image coding may be according to ITU-T Recs. T.4
(one- and two-dimensional) and Rec. T.6. Bitmap may also be specified.
Both facsimile style least significant bit and industry style most
significant bit mapping are supported.
(Definition courtesy of hrs1@cbnewsi.cb.att.com (herman.r.silbiger)
- APPLI/COM
- The name for the ITU-T API for computer-based facsimile.
See T.611 below for more information.
- Bell 103
- A standard for 300 bps full duplex dial-up modems. Popular in the
U.S. and Canada. In Europe the preferred standard is
V.21.
(Not used in fax but frequently supported by modems that handle fax.)
- BFT or
- Binary File Transfer
- A method of transferring files using fax modems (as an extension to the
fax protocol). The ITU-T standard for BFT is T.434.
The US version is TIA/EIA-614.
- Brooktrout Patent (taken from a press release from Brooktrout)
- Brooktrout's patent (number 4,918,722), issued by the US patent office
in 1990, covers generally any method for the selection of facsimile messages
and their deliver to a particular telephone number under control of commands
entered through a telephone, for example in the form of signals generated
from the telephone's touch-tone keypad. This method is employed in many
fax-on-demand systems, which provide business users and service providers the
ability to offer automated fax delivery of specified information in response
to requests from customers, subscribers or other callers.
[Editor's note: this patent is the subject of litigation and the current
status or validity of this patent is not known.]
- CAS
- An API for fax devices invented by Intel and DCA and tied to the Intel
and MS-DOS architectures.
The full text of the specification may be obtained from
ftp://ftp.faximum.com/pub/documents/cas.txt.
- CCITT
- Comite Consultatif International Telegraphique et Telephonique (a.k.a. The
International Telegraph and Telephone Consultative Committee). The old
name for ITU-T, the body responsible for setting the
international standards for telecommunications equipment.
See ITU below.
- CED or
Called Station Identifier
- The distinctive tone generated by a Group III fax machine when it
answers the phone (2100 Hz).
- Class 1
- The Class 1 fax modem standard describes an extension to the "Hayes Modem
Command Set" to permit computers to send and receive faxes using fax modems.
The Class 1 standard is a low-level specification in which most of the
protocol work (i.e. T.30) as well as image generation (rasterising and T.4
compression) must be done by the computer (in software) while the modem only
handles the basic modulation as well as converting the asynchronous data
from the computer into the synchronous packets used in fax communications.
The primary advantage of Class 1 modems is that fax protocol is implemented
in software which means that new extensions to the fax protocol standard
(i.e. T.30) can be implemented without requiring a ROM change in the modem
(or without waiting for the modem manufacturer to get around to supporting
the new feature). Also software developers are not dependent on the quality
of the T.30 firmware in the modem (as are developers who use Class 2 modems).
The primary disadvantages are (a) the software vendor has to handle the
complexity of the T.30 protocol and (b) Class 1 is very sensitive to timing
and multi-tasking operating systems (such as *IX) have great difficulty in
reliably meeting the tight timing constraints and maintaining the fax
connection. Lifting this timing limitation is the primary motivation
behind the new proposed Class 4 standard.
The official standard for Class 1 is EIA/TIA-578. (Note that if you are
purchasing a copy of EIA/TIA-578 be sure to purchase also the
TIA/EIA Telecommunications Systems Bulletin 43 (TSB43)
which provides additional information
missing from, or incorrect in, the original EIA/TIA-578 standard.
The ITU-T has approved an international version of the Class 1 standard
and designated it T.31. Note that T.31 includes a number of things not
in Class 1.
Although the official standard is copyright EIA/TIA/ANSI, a draft version
has been published electronically by Supra and is available from their
BBS and FTP sites (see sections I.10, and
I.15) and from Sam Leffler at SGI
(retrieve his HylaFAX package, described in section P.1).
- Class 2
- The Class 2 fax modem standard describes an extension to the "Hayes Modem
Command Set" to permit computers to send and receive faxes using fax modems.
The Class 2 standard is a higher-level specification in which most of the
protocol work (i.e. T.30) is done by the modem while the computer is
responsible for managing the session and providing the image data in the
appropriate format (i.e. T.4).
The priimary advantage of Class 2 is that the low-level detail work is
handled by the modem. Not only does this mean that software developers
do not have to be burdened with having to support the T.30 protocol, it
also relieves the host computer of all of the time-critical aspects of
fax communications, making support of Class 2 modems under *IX systems
possible.
The biggest headache for software developers is that the Class 2 standard
took a long time to be approved (more for political than technical reasons,
IMHO) and many companies did not wait for the final version to be approved
before shipping modems. As a result we have a situation (as of 93Q4) in
which all shipping Class 2 modems adhere (more or less) to the first draft
of the TR29.2 committee (document SP-2388) and not to the standard as it
was approved. To compensate for this, the "new" Class 2 is referred to as
Class 2.0 and the "old" as plain Class 2.
(Warning - flame from a frustrated fax programmer on...)
Even more disconcerting is the fact that most companies who have implemented
(the old) Class 2 have done one or more things wrong (they must have been
smoking *and* inhaling) so we have a further division of the standard into
"true, old Class 2" (which includes the Everex 24/96D and MultiTech modems)
and everything else (mostly based on the Rockwell chip which differs from
SP-2388 in a number of ways, although some other chip makers, such as EXAR,
have found even more ways than Rockwell to depart from SP-2388). It's so bad
that most modem companies now implement the Rockwell version of Class 2 just
because so many of the *%#& things have been shipped (i.e. Multitech has a
special command which switches their modem from proper Class 2 operation to
Rockwell-like operation just so they can interoperate with DOS software that
expects Rockwell-like operation). And of course no one at Rockwell or EXAR
or the other companies bothered to write down the difference between their
version of Class 2 and the TR29.2 document. (Flame off.)
The draft standard for the "old" Class 2 is SP-2388, Document
TR-29/89-21R8, dated March 21, 1990. This is available by contacting the
EIA/TIA directly. This is the standard implemented by all Class 2 modems
on the market prior to the end of 1993.
The official standard for the "new" Class 2 (also referred to as Class 2.0)
is EIA/TIA/ANSI-592. This document is available from Global Engineering Documents (see below).
As of 94Q4 the only modems known to the editor of this FAQ that support
2.0 are those produced by USRobotics and ZyXEL.
Note that although many modems that implement Class 2 also support Class 1,
Class 1 is *not* a subset of Class 2. Also, there are some modems that only
support Class 2 and many that only support Class 1.
Although the official standard is copyright EIA/TIA/ANSI, a draft version
has been published electronically by Supra and is available from their
BBS and FTP sites (see sections I.10, and
I.15) and from Sam Leffler at SGI
(retrieve his HylaFax package, described in section P.1).
The ITU-T has approved an international version of the Class 2.0 standard
(along with the TIA/EIA-605 Data Link Protocol)
and designated it T.32. Note that T.32 includes a number of things not
in Class 2.
- Class 3
- A class number reserved for a project to define a standard for fax modems
that would, in addition to handling the T.30 protocol (i.e. Class 2), also
handle the conversion of ASCII data streams into images (i.e. T.4). Although
there are a couple of fax modems that handle the ASCII to fax conversion,
no draft document has been circulated and the future of this project is in
doubt. It is expected that the functionality which were to be covered by
the Class 3 project will be rolled into the MFPI work (Multi-Function
Peripheral Interface).
- Class 4
- Class 1 with intelligent buffering to reduce the need for the host
computer to respond instantly to the fax modem. Although there is a
draft of this standard, the editor has resigned and the project to
complete this standard is on hold until a new project editor is found.
- Class 8
- Not a fax standard at all but an extension to the Hayes command set to
support voice. The interim standard covering voice extensions to the AT
command set is designated IS-101.
- CNG or
Calling Tone
- The distinctive tone that a fax machine ought to generate when placing
a fax call (1100 Hz on for 1/2 second, off for 3 seconds). Note that the
Group 3 fax standard only requires fax machines in "automatic operation"
to generate this tone so that machines which require you to dial the
number (either on the keypad of the fax machine or using an attached
phone) need not generate this tone. The lack of CNG can cause some
fax switches (see Q.9 below) problems.
There has been a proposal to change the Group 3 standard to mandate CNG
on all fax calls.
- CSI or
Called Subscriber Information
- The "name" of the answering fax machine. An optional frame of information
sent to the calling fax machine during Phase B (see T.30 below). Although
many fax machines permit ASCII information, the T.30 standard states that
this is to contain the international phone number of the fax machine,
including the plus symbol, the country code, the area code, and the
subscriber number using only digits, the plus symbol, and a space.
(i.e. the North American fax number (604) 926-8182 ought to be programmed
into the fax machine as +1 604 926 8182).
- DID or Direct Inward Dialling
- A special type of phone line (trunk) provided by the telco which associates
multiple phone numbers with a single telephone line and which send a signal
down the line when a call arrives which indicates which number was used to
place this call.
In some sense DID can be viewed as the opposite of Caller ID. With Caller
ID the signal indicates which number placed the call (i.e. the phone number
of the originator of the call). With DID the signal indicates which number
was dialled (i.e. the phone number of the destination of the call).
Note, however, that the signalling mechanism used for Caller ID is different
from the method used for DID. In other words, equipment that can decode the
Caller ID signals will not work on a DID trunk.
Historically DID has been used by PBXs that provided direct dialling to
internal extensions. For example, dialling 555-1201 would ring on
extension 101. Dialling 555-1202 would come in on the same trunk to
the PBX but the PBX would route the call to extension 102.
Now DID is also used with fax modems and boards to provide routing of
inbound faxes. Each employee or department is given a different fax number
but all of the calls come in on the same DID trunk. The fax board (or
external DID decode box) decodes the signal from the telco central office
which indicates which number was dialled and uses this number to route the
fax to the appropriate user or department.
- ECM or
Error Correcting Mode
- An extension to T.30 to permit the receiving fax machine to request that
portions of an image that were received with errors be retransmitted.
Normally the T.4/T.30 protocol is error detecting but not error correcting.
The receiving fax machine can usually tell when an error has impaired the
image but cannot selectively request retransmission of the damaged portions
of the image. The only options are to (a) ignore the errors (if few in
number), (b) request that the page be resent (ignored by most fax machines),
or (c) give up.
- EIA/TIA
- The Electronics Industry Association and the Telecommunications Industry
Association. The U.S. bodies responsible for the development of standards
related to telecommunications in general and for fax in particular.
- EIA/TIA-465
- The US version of T.4 (will probably be accepted as T.4 in the near
future).
- EIA/TIA-466
- The US version of T.30 (will probably be accepted
as T.30 in the near future).
- EIA/TIA-530
- The US version of something or other related to fax.
Need more information.
- EIA/TIA-578
- See the definition of Class 1 (above).
- EIA/TIA-592
- See the definition of Class 2 (above).
- EIA/TIA-602
- The ANSI/EIA/TIA standard for the "Hayes Command Set" for modems.
- EIA/TIA-614
- The ANSI/EIA/TIA standard for Binary File Transfer
(see BFT above).
- FaxBios
- An industry consortium (including companies such as Everex, HP, WordPerfect,
etc.) that has published a specification for a FAX API. Versions for
DOS and WINDOWS have been developed and discussions continue on adapting
this API to other operating systems.
With the demise of Everex the association seems to have collapsed leaving
WordPerfect as the only significant company supporting and promoting the
FaxBios standard.
- Group I Fax
- An old (now obsolete) standard for fax machines in which a page was
transmitted in about six minutes at a resolution of 98 scan lines/inch.
Group I devices frequently worked by attaching the page to be transmitted
to a rotating drum (at 180 rpm) along which a photocell moves. Either
amplitude modulation (the blacker the pixel the louder the tone) or
frequency modulation (the blacker the pixel the higher the tone) can be used.
The gory details may be found in ITU-T Recommendation T.2.
- Group II Fax
- An old (now almost obsolete) standard for fax machines in which a page was
transmitted in about three minutes at a resolution of 100 scan lines/inch.
Group II uses vestigial sideband amplitude modulation with phase shifts.
A white pixel is represented by a louder tone.
- Group III
- One of the current standards for fax machines in which a page is transmitted
in about one minute. See the definition of T.30 (below) for more details.
- Group IV
- A standard for fax transmission using ISDN at 64kbps.
- IS-101
- The Interim Standard developed and published by the TIA 29.2 committee
for voice modems (a set of extensions to the AT modem command set to
support voice recording and playback with modems).
- IS-141
- The Interim Standard developed and published by the TIA 29.1 committee
for subaddressing. (See Subaddressing below.)
- IS-650
- The Interim Standard developed and published by the TIA 29.1 committee
for Multi-Function Peripheral Interfaces (MFPI). This provides a method
for communicating with devices that support multiple functions such as
fax, printing, and scanning. Such devices are expected to be connected
to the host computer using either a single serial link or a bi-directional
parallel port.
- ITU and
ITU-T
- The International Telecommunication Union (ITU) is the United Nations
specialized agency dealing with telecommunications.
The purposes of the ITU as defined in the Convention are:
- to maintain and extend international cooperation for the improvement
and rational use of telecommunication of all kinds;
- to promote the development of technical facilities and their most
efficient operation with a view to improving the efficiency of
telecommunication services, increasing their usefulness and making
them, so far as possible, generally available to the public;
- to harmonize the actions of nations in the attainment of those
common ends.
The ITU works to fulfil these basic purposes in three main ways:
- international conferences and meetings;
- technical cooperation;
- publication of information, world exhibitions.
The ITU is an organization, a union, of Member countries. As of 1993 there
were 166 Members. The Union's headquarters are in Geneva, in the Place des
Nations.
Before 1993, the ITU consisted organizationally of five permanent organs:
the General Secretariat, the International Frequency Registration Board
(IFRB), the International Radio Consultative Committee (CCIR), the
International Telegraph and Telephone Consultative Committee (CCITT) and
the Telecommunications Development Bureau (BDT).
In early 1993, the ITU was reorganized into the General Secretariat and
three Sectors: Radiocommunication, Telecommunication Standardization and
Telecommunication Development. The standards-making activities of the
CCITT and CCIR have been consolidated into the Telecommunication
Standardization Sector (ITU-T). The remainder of CCIR activities were
integrated with the activities of the IFRB into the Radiocommunication
Sector (ITU-R). The Development Sector (ITU-D) facilitates
telecommunications development by offering technical cooperation and
assistance. The ITU General Secretariat supports the activities of the
three Sectors.
(This description has been taken from material published by the ITU.)
The standards promulgated by the ITU-T are called Recommendations and
the recommendations of relevance to the fax world are the T series which
govern the fax protocols and the V series which govern modem operation.
(See also T.*, and V.*, below.)
For more information on the ITU and the publications available from
them, see the description of ITUDOC in section I.10 in Part 2 of
this FAQ.
- MH or Modified Huffman compression
- Also known as Group III one-dimensional compression. See T.4.
- MR or Modified READ compression
- Also known as Group III two-dimensional compression. See T.4.
- One-Dimensional Compression
- See T.4
- PostScript Fax
- PostScript Fax has to be considered in two pieces:
First, we added G3 fax compatability to printers. The device accepts
PS jobs from the Mac, PC, and Unix hosts (we have host driver support
for all three) rasterizes these jobs at G3 resolutions with optional
cover pages and captions, and then sends the fax. You get all of the
usual bells and whistles like broadcast, delay, whatever. This differs
from a "normal" fax machine in that you avoid printing and rescanning
and thus get to transmit very high quality without extra effort. It
differs from a PC fax modem because it is network shareable thus saving
hardware and phone line charges. Our testing shows that our imaging is
higher quality than popular PC fax programs, but there's no intrinsic
reason they couldn't do just as well. Also, the fax modems tend to
drag down the PC while sending or receiving, whereas we offload the
really hard work of controlling the modem to the printer (yes, you
can still print while transmitting).
When we receive a G3 we automatically print it out, scaled to fit the
available paper if necessary. This plain paper output is much nicer than
a roll-fed device can produce. There's a trade-off vs. a PC fax modem.
With PS Fax you don't have to leave your PC on to receive faxes,
just your printer (which probably has a sleep mode), and you don't have to
deal with the very slow printing speed that many fax modem packages seem to
suffer from. But, if you wanted that file on the PC so you could edit
it or re-transmnit it or... Well, we don't support receiving back to
the PC yet.
One obvious difference from a traditional fax machine is that PS Fax
printers do not yet offer a scanner. Unless you have a scanner for your
PC, there's no way to fax clippings or handwritten documents with PS Fax.
Obviously, the "wonder box" printer, fax, copier, scanner is our next
target.
The other half of the equation is a thing called Postscript File Transfer.
If both you and the person you're communicating with have PS Fax devices
then the PS file gets sent rather than a G3. This usually results in
a shorter phone call and it always results in significantly higher
document quality including high resolution (ex 600 dpi), large format,
color, etc. Compared to 30 million G3 units the PS Fax installed base
is small, so the PSFT trick is only likely to work in closed environments.
It's been most successful either in big corporations who use it to
communicate between offices or for consultants who have a need to transmit
very high quality output to their clients and can talk their clients into
buying a PS Fax receiver.
Courtesy of mparker@mv.us.adobe.com (Mike Parker).
You can also obtain more information on PostScript Fax from Adobe's
WWW server:
http://www.adobe.com/PS/PSFax.html.
- SP-2388
- The first draft standard for Class 2 that was implemented by many
companies while waiting for the final standard to be approved
(see also the definition for Class 2 above).
- Subaddressing
- Subaddressing is a new feature added to the T.30 protocol to permit
the sending fax to specify where the fax is to be delivered by the receiver.
The subaddress consists of 20 characters limited to
the digits 0-9, space, *, and #.
The idea is that the sending fax machine allows the user to enter the
fax routing information after the fax phone by pressing the # key on the DTMF
keypad (note that most machines do not currently support this so do not
try this at home, kids).
The syntax of the subaddress field are spelled out in TIA/EIA IS-141
which defines the concept of fax extensions and fax forwarding.
For example, to send the fax to "fax extension" 1234 at fax number
1 604 926 8182 one would type on the fax machine's keypad
"1 604 926 8182#1234"
According to IS-141 it is possible to request the receiving fax machine
distribute copies of the fax to multiple destinations or even forward it to
another fax machine.
- T.2
- See Group I Fax. Not to be confused with T-1, a digital telephony
standard that runs at 1.544 Mb/s (at least in North America).
- T.3
- See Group II Fax.
- T.4
- One of the ITU-T recommendations (i.e. standard) for Group III fax.
In particular, this recommendation covers the page size, resolution,
transmission time, and coding schemes supported for Group III fax.
(See also the definition of T.30 below.)
The basic coding scheme (called in the recommendation "One-dimensional coding
scheme" but also known in the industry as MH or Modified Huffman) takes each
scan line of pixels and compresses it by (a) converting the raster in a
sequence of run lengths (the number of white pixels followed by the number
of black pixels followed by the number of white pixels etc. and etc. until
the entire raster has been converted into runlengths) and (b) encoding each
run length into a unique variable-length bit string. The code words used
for white and black runlengths are different and have been chosen in order
to do a reasonable job of compressing a "typical" fax page.
For example, in one dimensional encoding the following raster:
OOOOOOOOOO****OOOOOO**OOOOOOO*OOOOOOOOO***...
converted into run lengths:
10 4 6 2 7 1 9 3 ...
encoded into MH bit strings:
00111 011 1110 11 1111 010 10100 10
(spaces have been added for readability and are not part of the
MH bit string)
Since our example has unusually short white run-length it does
not accurately illustrate the degree of compression which can
be achieved. For example, a normal fine resolution fax image
contains about 3,800,000 pixels (464K). Using one-dimensional
encoding this can be reduced to between 20K - 50K.
In two-dimensional encoding, the first line of a group of lines is compressed
using one-dimensional coding (see above) and subsequent lines are compressed
using an algorithm that describes line n in terms of line n-1. Since there
is usually a high-degree of correlation between the pixels of adjacent scan
lines, this usually results in significant compression.
Since the basic fax protocol (T.30) is error detecting (but not error
correcting), there is a limit on the number of two-dimensionally compressed
scan lines that can follow a 1-D line. This is to limit the propagation
of errors through an image. This limit is referred to as 'k' in the
standard and is 2 for standard-resolution faxes and 4 for high-resolution
faxes.
Unfortunately, this method of compression is computationally intensive and
most (inexpensive) fax machines do not support it.
See Standards Related to Facsimile Communication
for information on how to obtain a copy of the T.4 standard.
- T.6
- The recommendation that covers the image compression algorithm used for
Group IV fax machines.
T.6 is essentially the two-dimensional compression algorithm from T.4 (see
above) except that 'k' is infinite (i.e. all lines are two dimensionally
compressed). This can be done because Group IV fax machines operate over
an error-free communications channel.
See Standards Related to Facsimile Communication
for information on how to obtain a copy of the T.6 standard.
- ITU-T recommendations (i.e. standard) for Group III fax.
In particular, this recommendation covers the protocol used to manage
the session and negotiate the capabilities supported by each fax machine.
The details of the image format are covered by the T.4 recommendation
(see above).
The protocol describes each fax call as proceeding through five phases:
- A: Call Set-Up
- This phase covers the placing of the call on the PSTN and the
distinctive tones the calling and called stations are to emit.
- B: Pre-Message Procedure for Identifying and Selecting Facilities
- During this phase the two fax machines:
- agree on whether to use tones or binary codes to exchange
information on capabilities (most current fax machines use
binary codes)
- (optionally) the called machine sends a CSI frame identifying
it to the calling machine.
- the called machine sends a DIS frame telling the calling
machine what capabilities it has (i.e. resolution, page
size, receiving speed, etc.)
- (optionally) the calling machine sends a TSI frame identifying
it to the called machine.
- the calling machine sends a DCS frame telling the called
machine what capabilities are in effect for this document
(based on the calling machine's capabilities and the information
received in the DIS frame).
- the two machines determine the maximum baud rate that the
communications link will reliable sustain (training & phasing)
- C: Message Transmission
- The fax is sent. The end of the last scan line is marked by a
RTC code (return to control).
- D: Post-Message Procedure including End-of-message, Confirmation,
and Multi-Page Procedures
-
- the calling machine indicates what it wants to do next
(send another page, terminate the call, request operator
intervention, etc.).
- the called machine indicates its response to the page and command
just received (o.k., o.k. but retrain, not o.k., give up, etc.)
At this point the machines go to one of phase B, C, or E depending
on the exchange of commands and responses during phase D.
- E: Call Release
- Hang up the phone.
See Standards Related to Facsimile Communication
for information on how to obtain a copy of the T.30 standard.
Gray Associates (manufacturers of fax protocol testing equipment) also
have an in-depth discussion of fax protocols at
http://www.grayfax.com/faxsminar.html.
- T.31
- The ITU-T version of the Class 1 standard.
- T.32
- The ITU-T version of the Class 2 standard.
- T.81
- The ITU-T recommendation for the use of JPEG compression for continuous
tone images in facsimile communications (i.e. colour fax).
- T.411 - T.418
- Open document architecture (ODA) and interchange format standards.
See Standards Related to Facsimile Communication
for information on how to obtain a copy of the T.41x standards.
- T.434
- The standard for Binary File Transfer Format (a method of encoding documents
and sending them by fax without converting them to image format first.
See Standards Related to Facsimile Communication
for information on how to obtain a copy of the T.434 standard.
- T.611
- Programmable communication interface (PCI) APPLI/COM for facsimile group
3, facsimile group 4, teletex and telex services. (i.e. an API for fax
services).
See Standards Related to Facsimile Communication
for information on how to obtain a copy of the T.611 standard.
- TIFF (Tagged Image File Format)
- The TIFF specification was developed by Aldus (now part of Adobe)
and Microsoft as a general file format for storing raster images.
A PostScript version of the specification may be obtained from
ftp://ftp.faximum.com/pub/documents/TIFF6.ps
The relevance of TIFF to fax is explained in the following entry.
- TIFF/F (Tagged Image File Format, Class F)
- The TIFF specification is an extremely general and extensible one
which makes it difficult to write programs which can dependable handle
all possible TIFF files. To simplify the problem somewhat the authors
of the TIFF specification have developed the concept of TIFF classes.
A TIFF class defines the tags that are required to be written by
TIFF writers (i.e. those tags that TIFF readers may depend upon) and
defines those tags (and tag values) which all TIFF readers of that class
must be able to handle.
TIFF Class F was developed by Joe Campbell while he was at Everex
developing the first Class 2 fax modem. The Class F specification
defines those tags (and by extension, those TIFF file formats) which
ought to be used and supported by fax software.
Many fax software companies support TIFF F files and some use it as
their native file format for received and transmitted faxes
(i.e. Faximum Software).
A flat-text version of the TIFF-F specification may be obtained from
i
ftp://ftp.faximum.com/pub/documents/tiff_f.txt
- TSI or
- Transmitting Subscriber Information
- The "name" of the calling fax machine. An optional frame of information
sent by the calling fax machine during Phase B (see T.30 above). See
CSI (above) for details on the recommended format.
- Two-Dimensional Compression
- See T.4.
- V.17
- The ITU-T recommendation for 14,400 bps *synchronous* half-duplex
modems. Used during the image transmission phase of fax
communications. Optional (most fax machines do not support V.17).
- V.21
- The ITU-T standard for 300 bps full duplex dial-up modems.
Popular in Europe. In U.S. and Canada the preferred standard is
Bell 103.
(Not used in fax but frequently supported by modems that handle fax.)
- V.22bis
- The ITU-T recommendation for 2400 bps asynchronous full-duplex modems.
(Not used in fax but frequently supported by modems that handle fax.)
- V.27ter
- The ITU-T recommendation for 2400 and 4800 bps *synchronous*
half-duplex modems. Used during the image transmission phase of fax
communications.
- V.29
- The ITU-T recommendation for 7200 and 9600 bps *synchronous*
half-duplex modems. Used during the image transmission phase of fax
communications.
- V.32
- The ITU-T recommendation for 9600 bps asynchronous full-duplex modems.
(Not used in fax but sometimes supported by modems that also handle fax.)
- V.32bis
- The ITU-T recommendation for 14,400 bps asynchronous full-duplex
modems. (Not used in fax but sometimes supported by modems that
also handle fax.)
- V.42
- The ITU-T recommendation for error-checking and correction.
(Not used in fax but sometimes supported by modems that also handle fax.)
- V.42bis
- The ITU-T recommendation for data compression.
(Not used in fax but sometimes supported by modems that also handle fax.)
- X.5
- The ITU-T recommentation for a Fax PAD facility
in a public data network.
- X.38
- The ITU-T recommentation for a Group 3 fax
equipment/DCE interface for equipment accessing the fax PAD facility in a
public data network.
- X.39
- The ITU-T recommentation for procedures for the
exchange of control information and user data between a fax PAD facility
and a packet mode DTE.