IBM xSeries 305 Type 8673 User Manual page 22

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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xSeries 305 Type 8673: User's Guide