IBM Personal Computer Manual To Operations page 73

Note: If you do not have an IBM
Communications Adapter Cable attached to
your system unit, go to the next page.
8
If you have an IBM Communications Adapter
Cable, it came with a wrap plug. Disconnect the
Communications Adapter Cable at the modem
end (refer to the Communications Adapter
Cable's "Option Installation Instructions" for
the cable-removal procedure).
9
See the figure below and install the wrap plug
(IBM part number 8529280) on the modem end
of the cable (end farthest from the system unit).
Communications Adapter
Cable Connector
(modem end)
/
Communications
Adapter Cable
Wrap Plug
April 1984 Start 20-3