Installing the 3Com Impact Digital Modem 2-3
Installing the 3Com Impact Digital Modem
This installation procedure assumes that you are familiar
with IBM and IBM-compatible or Apple Macintosh
computers. If you are not, refer to the user guide that
accompanied your computer for instructions on hardware
installation and operating system commands.

Installing the Digital Modem in an IBM-compatible PC

To install the 3Com Impact digital modem model 3C870 or
3C872 in an IBM or IBM-compatible computer:
1Turn off the computer.
2Ensure that the 3Com Impact digital modem power switch
is in the Off position.
3Insert the 9-pin male end of the 3Com Impact digital
modem-to-PC serial signal cable into the connector
labeled Computer on the digital modem’s back panel and
tighten the connector screws.
4Connect the other end of the 3Com Impact digital
modem-to-PC serial signal cable to a serial
communications (COM) port on the back of your PC and
tighten the connector screws.
Most COM port connectors are labeled COM, SERIAL, or
RS-232-C. On an IBM AT PC and most laptops or notebooks,
connect the cable to a 9-pin COM port connector.
5Connect the 3Com Impact digital modem power cable to the
connector marked 12V AC on the back panel of the digital
modem.
See Figure 2-1 for the location of the 12V AC connector on
the digital modem’s back panel.
6Plug the transformer end of the power cable into a
standard 117V ac wall outlet.