4-10 IBM Personal Computer User Guide
Setting up communications
If your computer has a fax/data modem, it can communicate with other computers
and fax machines.
Some IBM personal computers have a modem already installed. However, if your
computer package comes with a modem but it is not in stalled, open the system and
install the modem first. Refer to sections “Opening the s ystem unit” o n page 7-5 and
“Adding and removing adapter cards” on page 8-4 for instructions.
Before your computer can use its modem, you must complete the procedures in the
following sections:
• “Connecting your modem to the telephone network”
• “Configuring your communications software”

Connecting your modem to the telephone network

Modems are designed to operate over the public switched telephone network
(PSTN or PSN). This is an analog network commonly used by most households.
Connect the modem to an analog network only. If you are not sure about your
telephone line, contact your local telephone company.
Before you connect your modem to a telephone network, read the safety notices in
“Safety information” on page xiii.
Attention!
• Excessive voltages can occur on telephone
lines, especially during lightning storms. To
avoid any possible damage to sensitive
electronic parts, unplug the computer and the
telephone cords during such storms.
• Some businesses, schools, and buildings have
digital telephone systems, known as digital
private branch exchange (PBX) systems. These
systems do not work with the modem.
Connecting your modem to a digital telephone
system might damage the modem.