Modem connections and standards 155
If you are having trouble connecting to other modems,
try following these guidelines:
• If you know what protocols are available on the
modem you are connecting to, enable a protocol on
your modem that is supported by the other modem.
Usually V.42 works best if both modems support it.
• If you frequently connect to bulletin boards, buy a
modem communications software program that
includes many different software protocols.
Different bulletin boards use different protocols.
• Many network services have their own proprietary
protocols. To connect to these services, you often
have to buy the protocol from the service. Other
network services rely on V.42 or MNP 4.
Connecting with other fax
modems
Fax machines and fax modems are classified into
Groups. Each Group classification indicates the
modem’s transmission rate and level of technological
advancement. The first fax machines were Group 1
machines. These machines, being the slowest, are
almost obsolete today. Group 2 machines, which are
faster than Group 1 machines and slower than Group 3
machines, are also nearly obsolete. 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 with Group 2 or Group 1 fax
machines.
If you purchase additional fax
software
If your computer came with factory installed fax
software, you can use this software to operate your
modem. You can also purchase additional fax software.
If you purchase another fax program, you must
configure this software with the settings used by any
factory installed fax software.
To communicate with a fax modem (or the fax portion of
a data modem), the fax software sends commands from
a specified command set. One of these command sets is
a revised version of the ATcommand set. This revised
version includes two different sets of commands:
Class 1 and Class 2. Some modems support one class
while others support both. The modem in your
computer supports Class 1 fax commands.
Note:
CAS and SENDFAX are two other commonly used
command sets. These command sets are not supported
by the modems already installed in IBM Aptiva PCs.
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