Dell C7017T User Manual page 48

If you press any button other than the power button, the following messages will appear
depending on the selected input:
If VGA, DP, HDMI1/MHL, HDMI2 or HDMI3 cable is not connected, a floating dialog box
as shown below appears. The monitor will enter Power Save Mode after 4 minutes if left
at this state.
48 Operating the Monitor