V. About Fax Modems
Since fax machines are essential business tools today, it has become a trend
for modem vendors to add fax capability to their products.
A fax machine is made up of a scanner, printer and fax modem. The sending fax
machine scans a sheet of paper and convert its image into a code for
transmission over the telephone line. The receiving machine reconverts the
codes and prints a facsimile of the original. (However, some fax modems can
send and receive fax, while others can only send but not receive fax.)
Here are some terms you'll need to know about fax modems:
Group 3 is the international standard for communication between two fax
devices (fax machines or fax boards). Fax machines have evolved over the past
20 years. Groups 1 and 2 fax machines transmit a single page at six and three
minutes respectively and were used throughout the 1970s. Group 3 transmits one
page in as little as 20 seconds (at 9600 bps). Group 3 resolution is 203x98
dpi in standard mode and 203x196 dpi in fine mode. Virtually all fax machines
sold in the market today are Group 3 units.
V.27ter is the modulation scheme used in Group 3 Facsimile for image transfer
at 2400 and 4800 bps.
V.29 is the modulation scheme used in Group 3 Facsimile for image transfer
over dial-up lines at 9600 and 7200 bps.
V.17 is a new CCITT standard. It's the modulation technique for use in
extended Group 3 Facsimile that allows 12000- and 14400-bps fax transmission.
CAS (Communications Application Specification) is a communications protocol
developed by Intel and DCA (the software company know for Crosstalk) for a
combination fax and modem board that allows personal computer users to
exchange data more easily with fax machines. CAS was introduced in 1988. It
has been supported in many applications software (e.g. WordPerfect).
In the past, no standard existed for a microcomputer to deal with a fax board.
As a result, the software for a particular fax board won't work with another
fax board from a different manufacturer. (Although CAS has been moderately
successfully, it hasn't become the industry standard.) The Electronic
Industries Association/Telecommunications Industry Association (EIA/TIA) has
been developing new standards (Class 1 & Class 2) for microcomputers to
communicate with fax modems. As a result, you can buy a software program that
will work with Class 1 (or Class 2) fax modems from different manufacturers.
The Class 1 standard provides minimal hardware support for sending a fax from
a microcomputer, while Class 2 adds over 40 AT-command set instructions and
places more functionality into the modem.
Note that the Class 2 standard is not expected to be finalized until August,
1992. In fact, most "Class 2" fax modems in the market today are based an
obsolete draft. (It has become epidemic for computer vendors to announce
products that are supposed to meet a standard while the standard doesn't even
A fax modem may not be as useful as you'd think. (Personally, I don't find fax
modems to be useful or reliable. But I know people who can't do without their
fax modems.) Fax modems are good for sending, but not receiving fax. You may
still need (or want) a fax machine even if you have a fax modem.
Fax machines are easy to use. Fax modems are not. Anyone that knows how to use
a phone can learn to use a fax machine within a few minutes. A fax machine
will work no matter what kind of computer you have. It also doesn't matter
what operating system or environment you are running on your computer.
To use a fax modem, you may need to use a (sometimes more than one) software
program. I use DOS, Windows, and OS/2 on my PC. The DOS software for the fax
board is clumsy and hard to use, the Windows software is easy but unbearably
slow. (A two-page resume took about 10 minutes to send with the fax board. I
can print it out and send it with a fax machine in less than 3 minutes.) And
the machine locked up many times while I tried do something else. (If you use
Microsoft Windows, you should know that unrecoverable application errors are
not gone. They are called general protection faults in Windows 3.1)
If you need to fax a printed document, you'll need to have a scanner to get it
into your computer. To print out a fax received by your fax modem, you'd need
a printer. Also, your computer needs to be on to receive fax.
However, there are several advantages for using a fax modem (if you can live
with its shortcomings):
It's worth noting that many documents that are faxed should be sent by e-mail.
(A high-tech employment agency recently asked me to fax my resume and then had
it re-typed into the computer. I suggested that I sent the resume by e-mail,
but they didn't use e-mail.)
- You won't have a paper jam if you're faxing a multi-page document.
- The software for fax boards are more flexible and versatile. A fax board
can be a life-saver if you regularly fax the same document to several people.
- You don't have to print out the document you want to fax if it's generated
with your computer. And the quality is better.
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