Apple PowerBook G3 - Manual (Page 53)

Using Your PowerBook and Connecting to a Network 53
What Modems Do
A modem allows your computer to communicate over telephone lines by converting
information from the digital format used by the computer to the analog format used by most
telephone systems. It dials the telephone number, establishes a connection with another
modem, and controls the flow of data so that communication takes place with optimal speed
and accuracy.
To exchange data over a telephone line, your modem and the remote modem must establish
a connection and agree on how data will be transmitted in these ways:
m Connection speed: Initially, your modem tries to connect at its fastest speed. If the
remote modem cannot connect at this speed, your modem tries to use the next highest
speed. The two modems continue this fallback process until they find the highest speed
supported by both.
There are several circumstances that may prevent your modem from communicating at its
fastest speed. For example, the telephone number you use to connect to your ISP may
not support the fastest speed of your modem.
m Error control: Error control ensures data accuracy. Your modem and the remote modem
must agree on an error control method. Your modem will try to use one of the methods it
supports. If the remote modem doesn’t support any of these methods, error control isn’t
used. Modems can still communicate reliably without error control.
m Data compression: Compression increases the speed of data transmission by up to four
times. Your modem will try to use one of the data compression methods it supports. If
the remote modem doesn’t support any of these methods, data compression isn’t used.
Modems can still communicate reliably without data compression.
Your modem is set up to make the best possible connection with other modems
automatically. You do not need to do anything.
Software for Your Modem
Your Macintosh PowerBook comes with modem software, including programs to connect to
the Internet and to send and receive faxes. Some of this software is already installed for you.
Other software, such as your fax software, needs to be installed from a separate CD that came
with your computer. For instructions on using these programs, see their electronic manuals
on your computer’s hard disk or on the CD that came with your computer.
Important The actual speed of data transmission can vary with line conditions. Because
Federal Communications Commission (FCC) rules restrict the power output of modems
used by service providers, transmission speeds are limited to 53 Kbps (53,000 bits per
second) in the United States. You can obtain speeds of 53 Kbps on downloads from an
Internet service provider (ISP) that uses K56flex modems.