IBM 3270 Hardware User's Manual page 119

6. CAUTION
This product is equipped with a power
cord and plug that is grounded for your
safety. To avoid a possible electrical
shock, do not alter this plug or plug it
into an ungrounded wall outlet.
Plug the system unit power cord back into the
wall outlet.
Continue with "Step 2. Run the Power-On Self
Test."
5-4 Book 1 - 3270 PC Work Station User's Guide