3Com U.S. Robotics 56K Voice User Manual page 32

5. Find an empty ISA expansion slot that's at least as long as the gold
edge of your modem. (ISA slots are dark plastic grooves lined with
metal.) Unscrew and remove the expansion slot cover. It is the long
narrow piece of metal that keeps dust from entering through the
opening perpendicular to the slot.
6. Holding the modem by each corner, align the gold edge with the empty
expansion slot. Push down gently until the modem snaps into the slot.
The diagram shows horizontally aligned expansion slots. Some
computers have vertically aligned slots. The instructions apply to both
styles.
You need to apply a little pressure to seat the modem properly.
Sometimes a gentle back and forth motion helps fit the modem all the
way into the slot. If you feel resistance, the modem may not be
properly lined up with the slot. Do not force it into the slot. Remove the
modem and try again.
26 56K Voice Faxmodem Internal - User's Guide
Internal Modem Installation with Windows 3.x