Q. - Frequently Asked Questions about Fax
In a word, no. Unless your data modem has specific additional
support for fax, you cannot communicate with fax devices using
a data (only) modem.
Simply put, the problem is that the modulation methods (tones)
used to communicate data are different from those used to communicate
faxes.
Typically the modulation schemes used for fax are synchronous
half-duplex while those used for data (at least by most UNIX and
PC people) are asynchronous and full-duplex.
Also, data modems, once they have negotiated a modulation scheme,
tend to continue with the same one through out the session. Fax
modems switch before and after each page between a high-speed
modulation scheme used to transmit the image data and a lower
(300 or 2400 bps) scheme to exchange control information.
The following table outlines this briefly (see also part 1 of
this FAQ for definitions of V.*).
| Date Rate |
Data Modulation Std |
Fax Modulation Std |
| 9,600 bps |
V.32
|
V.29
|
| 14,400bps |
V.32bis
|
V.17
|
In a word, maybe. There is a standard proposed by the EIA/TIA/ANSI
called Binary File Transfer (BFT) that extends the fax Group III
modulation and protocols for bulk data transfer.
The problem, of course, is that few fax modems or software packages
provide support for this mechanism.
In addition to the basic software to drive your fax modem/board,
you will need specific software that can convert PostScript or
PCL files into a raster image format compatible with your fax
software package.
GhostScript, for example, is a publically available software
package that can convert PostScript into raster image format (although
there are varying opinions on the quality of the font support).
In the commercial world, most of the vendors of fax software
provide software that can handle PostScript and/or PCL.
When purchasing such software (a) check how many different fonts
are supported (it's a pain to be able to use, say, NewCentury
on your laser printer only to find it is not included in your
fax package), and (b) in the case of PCL, check which level of
the language is supported (PCL-4 does not support scalable fonts,
PCL-5 does).
In the PD world, there are a number of image-viewing packages
available for X (such as xv).
In the commercial world, most fax vendors provide support for
the commonly available devices (in the case of UNIX, X; in the
case of PC-UNIX, VGA and HGA support. Some vendors support other
graphics-capable terminals such as the Wyse WY-160.)
Most fax software packages include software to convert fax images
into print data streams compatible with dot matrix, HP PCL, or
PostScript printers.
Also the publically available (where?) pbmplus filter kit will
handle most image formats.
Not all fax boards can handle data (some are fax only). Most
(all?) external fax modems can handle data as well as fax.
Some (but not all) fax modems and software can automatically
distinguish between data and fax calls and answer them appropriately.
Some DOS/WINDOWS based products can automatically distinguish
between voice and fax/data calls and operate as a digital answer
machine as well as a fax machine.
Also, several companies sell devices which can switch incoming
calls between a fax machine, a telephone answering machine, and
a modem.
[Suggestions anyone?]
The standard resolution for faxes is 3.85 scan lines/mm (approx.
98 dpi vertically) with 1728 pixels across a standard scan line
of 215 mm (approx. 204 dpi horizontally).
The optional "fine" resolution is 7.7 scan lines/mm (approx.
196 dpi vertically) with the same horizontal resolution.
Many Group III fax machines use non-standard frames to negotiate
higher resolutions (typically 300x300 dpi and 400x400 dpi) with
other fax machines by the same manufacturer.
Two fax machines (or modems) must negotiate a common resolution,
page width, and page length before sending each page. The standard
requires that all Group III fax machines suppport at least standard
resolution and A4 size so that common ground can always be found.
Extensions to the Group III standard to support these higher
resolutions in a standard way have been proposed. Their current
status is not known [Need more information].
[Need more information on resolutions supported by Group IV].
When faxes exchange information, it is done in the form of compressed
images (with the exception of BFT). If you wish to edit or otherwise
manipulate a received fax file you have two options:
- edit the file using a "paint" program that will accept the
fax file (unfortunately there is a wide range of file formats
for image files and you may have to work to find a format that
is common between your fax application and your paint program).
- pass the file through an OCR program that will attempt to
convert the image into ASCII (or word processing file format).
The problem here is that most OCR programs are tuned to work
with 300x300dpi images and faxes are either 98x204 or 196x204.
There are many API's that are used for fax communications. Words
marked by -word- are further explained in the glossary in Part
1 of this FAQ.
At the hardware level, the two standards that govern the exchange
of commands between a host computer and a fax modem are EIA-578
(-Class 1-) and EIA-592 (-Class 2-).
At the software level there is one "official" standard and a
number of "industry standards". The one "official" standard is
ITU-T T.611 ([need more information on this standard]).
The most widely known industry standards are -CAS- (Communicating
Applications Standard (?)) invented by Intel and DCA and tied
closely to the Intel architecture, and -FaxBios- (developed by
an industry consortium) which is less machine-dependent (implementations
for MS-DOS and WINDOWS have been published and sporadic work on
UNIX and other bindings is underway).
There are a number of devices on the market (suggestions from
happy campers welcome) that will try to distinguish between an
incoming voice, fax, or data call and route the call appropriately.
These fax switches attach to the phone line and then the other
devices (your normal voice phone/answering machine, fax machine,
data modem, etc.) are attached to the fax switch).
All devices work on one of two general principles: listening
for CNG or voice, or listening for distinctive ring patterns (cadences).
In the first case the device will answer the phone and try to
guess what it should do based on what it hears. Some machines
play back a sound of a phone ringing so that humans dialling in
think the phone is still ringing when in fact the fax switch is
listening to see if the call is from a fax machine or a human.
If the CNG tone (see Part 1 for a definition of CNG) from the
calling fax machine is heard, then the switch connects the call
to the fax machine, otherwise the call is deemed to be a voice
call and is connected to your phone/answering machine.
A slightly more sophisticated approach is for the fax switch
to answer the phone and play a short recorded announcement. If,
during the announcement the CNG tone is heard, then the call is
switched to the fax machine. If no CNG tone is heard but sound
is heard after the announcement, then the call is assumed to be
voice and switched appropriately. If nothing is heard then the
switch either considers the call a data call and switches it to
a modem or considers it a fax call from a machine that does not
generate a CNG and switches it to the fax machine.
The other approach relies upon an optional service available
from some telcos called "SmartRing", "Distinctive Ring", "RingMaster",
"Ident-a-Ring", etc. This feature allows one to have more than
one phone number associated with the same phone line. Incoming
calls using the different phone numbers can be differentiated
by the different ringing patterns (i.e. one long ring, two short
rings, three short rings, etc.) The fax switch distributes the
call based on the ring cadence it detects.
The advantage of the first approach is that one does not have
to send more money to the phone company (or depend upon the availability
of the "SmartRing" feature being available). The disadvantage
is that it is not always reliable (especially in the face of fax
machines that do not generate CNG tones).
The advantage of the second approach is that it is very very
reliable. The disadvantage is that it requires the availability
of the "SmartRing" feature from one's telco as well as sending
more money to the telco every month.
There are several services (commercial as well as free) that
offer to accept e-mail messages and fax them to the specified
phone number.
To obtain information on the free service, see http://www.tpc.int/
To obtain information on the commercial services, see:
http://www.awa.com/faxinet/faxinet.html
http://www.faxsav.com/
See also http://www.savetz.com/fax/
Note that the following is provided for your information
only and is not to be considered or taken as legal advise. You
are recommended to contact a lawyer in your jurisdiction should
you need information on the legal issues related to facsimile
communications.
American (USA) Law
***** FCC January 11, 1993 Public Notice *****
FEDERAL COMMUNICATIONS COMMISSION
PUBLIC NOTICE (31291 / DA 92-1716) January 11, 1993
INDUSTRY BULLETIN
TELEPHONE CONSUMER PROTECTION ACT
TELEPHONE SOLICITATIONS, AUTODIALED AND ARTIFICIAL OR PRERECORDED
VOICE MESSAGE TELEPHONE CALLS, AND THE USE OF FACSIMILE MACHINES
The Telephone Consumer Protection Act (TCPA) is a federal statute
that was enacted on December 20, 1991, to address concerns about
the growing volume of unsolicited telephone marketing calls and
the increasing use of automated and prerecorded telephone calls.
The TCPA imposes restrictions on the use of automatic telephone
dialing systems ("autodialers"), artificial or prerecorded voice
messages, and telephone facsimile machines to send unsolicited
advertisements. The TCPA also directs the FCC to adopt regulations
to protect residential telephone subscribers' privacy rights to
avoid receiving telephone solicitations to which they object.
The FCC adopted rules and regulations, effective December 20,
1992, implementing the TCPA. The FCC will be monitoring complaints
about automated calls and unwanted telephone solicitations to
determine whether additional action to limit or to prohibit such
calls would be appropriate.
DO FCC RULES BAN UNSOLICITED ADVERTISEMENTS TO TELEPHONE FACSIMILE
MACHINES?
Yes. Effective December 20, 1992, FCC rules ban the transmission
of unsolicited advertisements to telephone facsimile machines.
An "unsolicited advertisement" is defined as a transmission advertising
the commercial availability or quality of property, goods or services
without the prior express invitation or permission of the person
or entity receiving the transmission.
Unsolicited advertisements may not be transmitted by any device
to a telephone facsimile machine unless the person receiving the
facsimile has given prior express invitation or permission to
receive it. If the sender and the recipient have an established
business relationship, an invitation or permission to receive
unsolicited facsimile advertisements is presumed to exist. However,
the recipient may end an established business relationship by
requesting that no further unsolicited advertisements be sent,
thus revoking any invitation or permission to receive further
transmissions.
WHAT OTHER REQUIREMENTS APPLY TO THE USE OR MANUFACTURE OF TELEPHONE
FACSIMILE MACHINES?
FCC rules require that each transmission to a telephone facsimile
machine must clearly contain, in a margin at the top or bottom
of each transmitted page or on the first page of the transmission,
(1) the date and time the transmission is sent (2) the identity
of the sender and (3) the telephone number of the sender or of
the sending machine. All telephone facsimile machines manufactured
on or after December 20, 1992 must have the capacity to clearly
mark such identifying information on the first page or on each
page of the transmission.
[Note, according to the FCC January 13, 1993 Public Notice, the
requirement to mark faxes with the above identifying information
on applied to fax machines and not for fax cards used in computers
pending reconsideration proceedings.]
WHO IS RESPONSIBLE FOR COMPLIANCE WITH FCC RULES ON TELEPHONE FACSIMILE
TRANSMISSIONS?
The person on whose behalf a facsimile transmission is sent will
ultimately be held liable for violations of the TCPA or FCC rules.
DO THE TCPA AND THE FCC'S RULES PREEMPT STATE LAW?
The TCPA specifically preempts state law where it conflicts with
the technical and procedural requirements for identification of
senders of telephone facsimile messages or automated artificial
or prerecorded voice messages.
The TCPA and the FCC's rules do not preempt state law which imposes
more restrictive requirements or regulations for (1) the use of
facsimile machines or other electronic devices to send unsolicited
advertisements, (2) the use of autodialers, (3) the use of artificial
or prerecorded voice messages, or (4) the making of telephone
solicitations.
Thus, depending on state law, the TCPA, the FCC's rules and/or
state laws could apply to your company's services. You should
contact the state public utilities commission in each state where
your company provides the services listed in the previous paragraph
to determine what laws apply in those states.
WHERE CAN I ORDER A COMPLETE COPY OF THE TCPA AND THE FCC'S ORDER
EXPLAINING IMPLEMENTATION OF THAT ACT?
Copies can be ordered from the FCC's contractor for public records
duplication: Downtown Copy Center, 1990 M Street, N.W., Suite
640, Washington, D.C. 20036 (telephone: (202) 452-1422). You should
ask for copies of the Telephone Consumer Protection Act and the
Report and Order in CC Docket No. 92-90 released by the Commission
on October 16, 1992 (In the Matter of Rules and Regulations Implementing
the Telephone Consumer Protection Act of 1991).
Canadian Law
OTTAWA-HULL, Nov. 7 (Canada NewsWire) -- The CRTC today approved
proposals to limit the hours during which uninvited facsimile
calls can be made for the purpose of solicitation in Bell Canada
and BC TEL territories. The Commission also shortened the interval
during which telemarketers must comply with a consumer's request
not to be faxed again (Telecom Order CRTC 96-1229).
``With the growing presence of fax machines in Canadian homes,
there have been many consumer complaints about the misuse of fax
advertising,'' said CRTC Chairperson Francoise Bertrand. ``Large
numbers of consumers have complained about facsimile calls waking
up their families in the middle of the night or tying up their
machines with unwanted ads, and about the time taken by some telemarketers
to comply with do not fax' requests.''
``Under the Telecommunications Act, the Commission has the responsibility
to protect citizens' privacy and prevent undue inconvenience or
nuisance from unsolicited telecommunications, while taking into
account the legitimate uses of such communications and the guarantee
of freedom of expression set out in the Charter of Rights. Overall,
we believe the measures approved today constitute an appropriate
balance between the protection of citizens' privacy and commercial
freedom of expression.''
``Nonetheless,'' Ms. Bertrand concluded, ``the CRTC will continue
monitoring consumer complaints regarding the use of facsimile
calls and will address the issue again if public annoyance continues
to be significant.''
As a result of today's decision, uninvited fax advertising in
the areas served by Bell and BC TEL will be permitted only during
the following hours: between 9 a.m. and 9:30 p.m. from Monday
to Friday; and between 10 a.m. and 6 p.m. on Saturday and Sunday.
These hours refer to the time zone of the called party.
In addition, telemarketers must remove names and numbers from
their faxing lists within seven days -- instead of the current
30 -- after a consumer asks. A subscriber's do not call' request
remains in effect for three years.
In accordance with previously established conditions for unsolicited
facsimile calls, telemarketers must provide sufficient information
to allow the subscriber to follow up on the call. They are also
required to display the originating calling number, or an alternate
number where they can be reached, unless number display is unavailable
for technical reasons. Sequential dialing is prohibited, and callers
using random dialing must ensure that no calls are made to emergency
lines and healthcare facilities. Callers who violate any of the
above conditions may have their service terminated by Bell or
BC TEL after two business days' notice.
Facsimile calls made for purposes other than solicitation (e.g.
emergency and other public service announcements, account information,
and market or survey research) are not subject to the new rules.
Similarly, these rules do not preclude facsimile calls by businesses
responding to messages or requests by telephone subscribers.
Copies of today's telecom order are available through our Internet
home page (http://www.crtc.gc.ca)
or by contacting the public examination room of any CRTC office:
| CITY |
TELEPHONE |
TDD |
FAX |
| Halifax |
(902) 426-7997 |
(902) 426-6997 |
(902) 426-2721 |
| Montreal |
(514) 283-6607 |
(514) 283-8316 |
(514) 283-3689 |
| Ottawa-Hull |
(819) 997-2429 |
(819) 994-0423 |
(819) 994-0218 |
| Winnipeg |
(204) 983-6306 |
(204) 983-8274 |
(204) 983-6317 |
| Vancouver |
(604) 666-2111 |
(604) 666-0778 |
(604) 666-8322 |
For further information: CRTC Public Affairs, Ottawa, K1A 0N2,
Tel: (819) 997-0313, TDD: (819) 994-0423, Fax: (819) 994-0218/
One of the problems with computer-based facsimile that was never
anticipated by the developers of the original fax standard was
the need to be able to route incoming faxes to the appropriate
user on a computer system or network.
Faxes arrive at a fax machine with no electronic addressing information
and only a typed or handwritten name on the cover sheet.
There are several methods available or proposed for the routing
of received faxes. They are listed below along with some of their
advantages and disadvantages.
-
Description:
Received faxes are examined at a workstation by an operator who
manually decides who ought to receive the fax. Depending on the
software being used this can be done using:
- a proprietary fax client
- an email client
- a web browser
The general concept is that the user can view the cover sheet
of each received fax and select the intended recipient from a
pull-down list. With well designed software it is possible to
route a fax in a matter of seconds -- far faster than manually
sorting, collating, and delivering hardcopy faxes.
Advantages:
- almost 100% reliability
- no special action or hardware required by sender
- no special hardware/software/telephone line required by receiver
- efficiency far higher than manual sorting of paper faxes
Disadvantages:
- manual intervention required
Description:
With this method an OCR software package tries to convert the
image of the cover sheet into text which is then scanned for the
name of the user the fax is to be routed to.
Advantarges:
- manual intervention not required
- no special action or hardware required by sender
- no special hardware/telephone line required by receiver
Disadvantages:
- low reliability (especially with standard resolution faxes)
- extra-cost software (about $1,600) needed
- only typed cover sheets
Description:
With this method an ICR software package tries to convert the
image of the cover sheet into text which is then scanned for the
name of the user the fax is to be routed to.
The difference between ICR and OCR is that ICR uses more powerful
(but much slower) neural net algorithms which can handle standard
resolution faxes as well as handwriting (printed).
Advantages:
- manual intervention not required
- no special action or hardware required by sender
- no special hardware/telephone line required by receiver
- better recognition than OCR (even with standard resolution
faxes and some handwriting).
Disadvantages:
- extra-cost software required (anywhere form $2,000 to $20,000
depending on package and platform) required
- reliability not 100%
Description:
A mechanism has been added to the T.30 fax protocol (in 1994)
to allow the sender of a fax to key in an extension number which
can be used by the receiver to route the fax.
For example, if a particular individual were to be associated
with fax extension 215, then the sender would dial (say): 9268182#215
The fax machine would dial 9268182 and send the extension number
(215 in this example) as the sub-address.
Advantages:
- manual intervention not required
- no special software/telephone line required by receiver
- 100% reliability (assuming the sender enters the extension
number).
Disadvantages:
- sender required to have a new fax machine with support for
subaddressing
- sender required to know how to use new fax machine and how
to enter sub-address
- fax modem which supports T.30 subaddressing required
Description
This method of routing is similar to T.30 sub-addressing in that
the sender enters a fax extension number when dialling the number
(i.e. 9268182#215). Technology never brought to market
by Novell.
Advantages:
- manual intervention not required
- no special software/telephone line required
- 100% reliability (assuming the sender enters the correct extension
number).
- sender not required to replace fax machine with newer model
(Novell intended to sell add-on devices for roughly $50 which
will add NEST routing to existing fax machines).
- no special modem or hardware required on receiving end
Disadvantages:
- sender required either to have a new fax machine with support
for NEST addressing or to have a NEST addressing device added
to their fax machine (neither of which ever reached the market)
- sender required to know how to use NEST addressing
- requires that vendor pay significant licence fees to Novell
- widespread acceptance of Novell's scheme is in doubt since
it has not been adopted by any official standards body (but
T.30 subaddressing has) and does not seem to provide any advantages
over T.30 subaddressing.
Description:
With this method the sender of the fax places a bar code (like
those found on groceries) on the cover sheet indicating the name
of the intended recipient.
Advantages:
- manual intervention not required for routing
- no special hardware/telephone line required by receiver
- reliability approaching 100%
Disadvantages:
- sender required to:
- be able to generate bar codes
- be willing to place bar code stickers on faxes or be willing
to use cover sheets provided by recipient
- routing covered by a patent and not generally available without
special licensing
Description:
With this method the TSI of the sending fax machine (i.e. the
phone number of the sender's fax machine) is used to route the
fax.
In other words, every fax from machine X goes to person Y.
Advantages:
- manual intervention not required for routing
- no special action or hardware required by sender
- no special hardware/software/telephone line required by receiver
- high reliability (100% when the sending fax machine is properly
configured with the correct TSI)
Disadvantages:
- requirement that the sending fax machine's TSI be properly
set
faxes from the same machine not permitted to go to different people
(i.e. the sender is not permited to select the recipient...all
faxes from a given machine end up being routed to the same user)
Description:
With this method the system has multiple fax lines and modems
and all faxes that are received on a given fax line are routed
to a particular user (or group of users).
Advantages:
- manual intervention for routing not required
- no special action or hardware required by sender
- 100% reliability
Disadvantages:
- separate phone line and fax modem for each user who wishes
to receive faxes required
Description:
Telephone companies in North America (and some other areas) can
provide a special telephone line (trunk) which is associated with
multiple phone numbers.
For example, a company could obtain a DID trunk from the telco
with a block of numbers (say 926-8110 through 926-8119).
If any of these nine numbers is dialled, the call will come in
on the same DID trunk. The difference is that before ring signal
is sent, the telco central office sends a special signal down
the line identifying which of the (in this case nine) numbers
was dialled.
In this manner the receiving device can differentiate between
a call to 926-8110 and 926-8115 (even though the two calls would
come in on the same phone line) and can route all calls (faxes)
to 926-8110 to one person and all calls (faxes) to 926-8115 to
someone else.
Advantages:
- manual intervention not required
- sender not required to have special fax machine or hardware
- 100% reliability (assuming the sender uses the correct fax
number).
Disadvantages:
- requirement for a special phone line from telephone company
that is more expensive that a standard (POTS) phone line.
- DID line not able to be used to outgoing faxes (requires an
additional standard phone line, although a single modem can
be shared between the DID and POTS line for both incoming and
outgoing faxes)
- special hardware and modem to intercept DID signalling information
required
Description:
Telephone companies outside of North America (and some other
areas) can provide a special ISDN telephone line (trunk) which
is associated with multiple phone numbers. (DDI is the ISDN equivalent
of DID, see above.)
Advantages:
- manual intervention not required
- sender not required to have special fax machine or hardware
- 100% reliability (assuming the sender uses the correct fax
number number).
Disadvantages:
- requirement for a special services on top of an ISDN phone
line from telephone company that may be more expensive that
a standard ISDN phone line.
- special hardware and/or modem to intercept DDI signalling
information required
Description:
DTMF routing requires the sender to manually dial the fax modem
and once the modem answers, type in a special routing code before
pressing the send button the fax machine.
The fax software at the receiving end looks up the number in
a table of users to determine the intended recipient.
Advantages:
- manual intervention not required on receiving end
- sender not required to have special fax machine or hardware
- 100% reliability (assuming the sender enters the correct DTMF
number).
Disadvantages:
- requires sender to go through contortions to manually dial
fax number, wait for answer, and then type in DTMF routing code
- requires modem that can recognise DTMF tones
|
