IBM Aptiva Handbook page 144

Your modem communications software determines how your
modem operates with Call Waiting. For specific instructions,
see the user's guide or online Help that came with the
communications software.
If your computer came with a fax software already installed,
use the fax software documentation included in your
computer package or the fax software online help for
additional information.
B-4 Appendix B: Modem information
This section provides information on the modem commands
if you operate your modem from the DOS prompt using the
AT command strings.
([HFXWLQJ FRPPDQGV
Your modem is in the Command Mode when powered-on
and is ready to receive and execute AT commands. The
modem remains in the Command Mode until it makes a
connection with a remote modem. Commands may be sent
to the modem from an attached terminal or a PC running a
communication program.
The modem is designed to operate at common DTE speeds
ranging from 300 bps to 115.2K bps. All commands and data
must be issued to the modem using one of the valid DTE
speeds.