Fax Modems; Choosing Fax Software Programs - IBM Aptiva Handbook

Fax modems

Fax modems send and receive facsimiles and generally
transmit and receive pictures better than text or other
data. In a fax machine, a page is read by a scanner and
broken into a series of dots representing light and dark
portions of the page. These dots compose the pictures,
graphics, letters, and numbers printed by the fax
machine.
The scan rate option in your fax software deter-
Important: mines the size of a fax and how much time it takes
to transmit the file.
The fax machine scans a page line-by-line and records
the number and position of each dot in a scan line. This
information is converted into a special code and
transmitted to another computer or fax machine. This
transmission uses a set of transfer and modulation
specifications called protocols.
Fax machines and modems are connected in Groups.
The Group a fax machine belongs to indicates its speed
and level of technological advancement. The original fax
machines were Group 1 machines. These are the
slowest machines and are almost obsolete today. Faster
Group 2 fax machines replaced the Group 1 machines.
Group 2 machines are also nearly obsolete today. Most
fax machines sold today are Group 3 machines.
Generally, a Group 3 fax machine can connect most
efficiently to another Group 3 machine and may also be
able to connect to many Group 2 machines. However, a
Group 2 machine cannot connect to a Group 3 machine.
The modem in your computer works with most Group 3
fax machines but not Group 2 or Group 1 fax machines.
168 Appendix C: Modem information
Choosing fax software
programs
If your computer did not come with fax software, you
must buy a fax software program to operate your fax
modem. Also, if you add a fax modem to your computer,
you need to purchase fax software.
You send commands to a fax modem (or the fax portion
of a data modem) using a revised version of the AT
command set. This revised version includes two
different sets of commands: Class 1 and Class 2. Some
modems support one class of command while others
support both. When buying a fax software program,
choose the highest class that your modem supports.
The modem in your computer supports class 2 fax
machines.
CAS and SENDFAX are two other commonly used com-
note: mand sets. These command sets are not supported by the
modems already installed in IBM Aptiva PCs.