IBM RT PC Options Installation page 169

Installing Display Options
CAUTION
Tum off the power on the system unit and unplug the power cable from
the electrical outlet.
If you have not removed the covers, see "Removing the Covers From the
System Units" on page 1-4.
Refer to "General Instructions" on page 3-4 when necessary for
information on installing adapters.
7 -4 Options Installation