3Com 56K User's Manual And Reference page 34

Follow the on-screen instructions to access the
COM port settings panel. In this panel you should
find the UART chip used. Match the UART type
listed in MSD with the serial rate listed in the chart.
Select this serial rate in any fax/data programs you
use.
If this is your UART... Select this serial rate
16550 115.2 or 57.6 Kbps
16450 38.4 Kbps
8250 19.2 Kbps
Do not select a 28,800, 14,400, or 12,000 bps serial
port rate if offered. Your modem will not work correctly
with any of these settings. Fix or lock the serial port
(baud) rate. If it's referred to as autobaud , select OFF
Congratulations!
You are now ready to start using your
3Com U.S. Robotics Professional Message
Modem
30
Software Installation
.