Apple Macintosh PowerBook Internal Modem/Ethernet - Manual (Page 4)

Using your modem
It’s a good idea to become familiar with a modem’s general operations. This
section explains what modems do and shows how to designate the PowerBook
G3 Internal Modem in the software you plan to use with the modem.
What modems do
Modems allow computers to communicate over telephone lines. While
computers manipulate information in digital format, most telephone systems
carry information as analog (wave) signals. Therefore, in order for computers
to communicate over the PSTN (Public Switched Telephone Network),
information must be converted to and from digital and analog formats. A
modem (modulator/demodulator) handles these format conversions. The
modem of the sending computer converts information from digital format to
an analog signal by a process called modulation. The modem of the receiving
computer converts the analog signal back to digital format by a process called
demodulation.
Modems also dial, establish connections, and control the flow of data across
the telephone line so that transmission takes place with optimal speed
and accuracy.
Preparing for a modem connection
Before two computers can exchange data over telephone lines, their modems
must establish a connection and agree on how data will be transmitted.
Your modem is already set to make the best possible connection
automatically. See “Technical Specifications,” later in this manual, for a list
of specifications.
Note: In general, it is best to use your modem’s automatic settings. If you
want to control the speed, error control, and data compression settings
yourself, see the Modem AT Command Set (a file on your hard disk) or the
user’s guide that came with your data communications software.
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