Carrier Performance EDGE Owner's Manual page 50

Hybrid Heat (heat pump with a furnace system only)
This thermostat works with the Carrier Hybrid Heat systems offering
maximum comfort and economy by automatically controllin 9 whether
your system delivers heatin 9 with the heat pump, with the furnace, or
with both options working together,
Service reminders
The thermostat tells you when it's time to change the UV light in the
evaporator coil box connected to the furnace (if equipped), humidifier
pad (if equipped), and furnace filter, Each reminder - check UVlight,
check hum pad, check filter - will be displayed on the upper left of
the screen, (For important safety reasons, ask your dealer to replace
your UV li9ht,) _ _
To remove the reminder after you or your dealer have
replaced the indicated product, press and hold the done
button for about three seconds, oooooo
Outdoor temperature display
The thermostat automatically displays the outdoor temperature only
when the door is closed,