IBM 5294 Setup Procedure page 16

Remove the plastic covering from the power cord
connection on the back of the controller (as shown).
Safety Precaution
Do not connect or disconnect a power cord during an electrical storm. You
could be seriously injured.
Plug the power cord into the power cord connection on the
back of the controller. Plug the other end of the power cord
into the grounded electrical outlet.
Chapter 2. Setup and Work Station Attachment 7