@ally CEV is Consumer Electronic Control
https://en.m.wikipedia.org/wiki/Consumer_Electronics_Control
the ability to interact with the system inside over the HDMI cable.
With the advent of the Energy star power saving program, displays, tvs, and other devices are required to turn off after a period of inactivity.
and are required to show a message that says
No Input, warning you about the impending power off
now your device is off and can’t be turned back on.
CEC provides a low power mechanism to request the device to do things. change channel, and also power on/off.