Dell E2015HV User Manual page 55

Activate the computer and wake up the monitor to gain access to the
OSD.
If you press any button other than the power button, the following
messages will appear depending on the selected input:
If VGA or DVI or DP cable is not connected, a floating dialog box as shown
below appears. The monitor will enter Power Save Mode after 5 minutes
if left at this state.
Operating the Monitor 55
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