IBM 3270 Option Instructions page 17

18.
Plug the system unit power cord into a properly grounded
power outlet.
19.
If you have the 3270 color display, plug its power cord
into a properly grounded power outlet.
20.
You are ready to check out your installation.
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To check out your installation, refer to "Checkout" in
your IBM 3270 Personal Computer Guide to Operations.
After a successful checkout, for information on the use
of the All Points Addressable Adapter, see your IBM 3270
Personal Computer Control Program User's Guide and
Reference.
AP A Adapter 13