IBM DS4200 Installation, User's, And Maintenance Manual page 16

Statement 5:
CAUTION:
The power control button on the device and the power switch on the power
supply do not turn off the electrical current supplied to the device. The device
also might have more than one power cord. To remove all electrical current
from the device, ensure that all power cords are disconnected from the power
source.
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IBM System Storage DS4200 Express Storage Subsystem: Installation, User's and Maintenance Guide