Carrier Performance Non-Programmable ADGE Owner's Manual page 37

"Auxheat on"isdisplayed (heat pump and Hybrid Heat s ystems only)
Aux heat on is auxiliary heat. It applies only to the heat pump version. If it is on,
you will see aux heat on. When it is displayed, it means the system has determined
that it's too cold outside for your heat pump to heat the house without help, so it's
getting help from the electric heaters. This happens automatically.
"Em heat" is displayed (heat pump and Hybrid Heat systems only)
Em heat is the display term for emergency heat and applies only to the heat pump
version. When emergency heat has been turned on, Em heat is displayed. You have
to turn on emergency heat manually - it doesn't happen automatically - so if you
see Em heat on the display, it means somebody has turned it on.
There is a power outage
If you lose electricity, you won't have to reprogram the thermostat because your
settings are retained in its memory.