Apple Power Macintosh 8600 - Manual (Page 45)

Choosing and connecting a modem
A modem is a piece of equipment that turns the data from your computer into
information that can be transmitted over telephone lines. The modem enables
your computer to send and receive telephone calls, to connect to the Internet,
to access online services, and to communicate with other computer users.
Some modems also allow you to transmit documents on your computer to fax
machines as well as receive faxes as documents that you can view on screen
or print.
Keep in mind that when your phone and a modem share a single phone line,
you will not be able to use both at the same time, even if they are attached to
separate phone jacks. While you use a modem, outside callers get a busy
signal and you cannot call out. Conversely, when you use your phone, you
cannot use the modem. (If you miss phone calls because you often use your
modem, you may want to get a second phone line installed or get a phone
company message service which, unlike an answering machine, will record
messages even when your phone is off the hook or you are online.)
Also keep in mind that long-distance charges accrue when your modem dials
long-distance numbers. In most cases, an online service or an Internet service
provider will have a local access phone number so that long-distance charges
do not apply.
45 Connecting Your Computer to a Telephone Line