Carrier TC-NAC Owner's Manual page 8

ON-SCREEN INDICATORS
1. Fan mode - on or auto
2. System is in auxiliary (supplemental) mode
3. Current temperature
4. Thermostat mode is either off or using emergency heat
5. Fahrenheit
6. Keypad is locked (no padlock means unlocked)
7. Celsius
8. Battery strength indicator
9. Selected cooling set point: "on" indicates system is in cooling mode
10. Second stage of cooling is active