Honeywell Rth3100c Digital Non-programmable Thermostat With Backlit Display Digital Thermometer Easy To Install And Use With Simplified Operation. Backlit Display Is Easy To See And Read. Emergency And Auxiliary Heat +/ Indication. Accurate Termperature Control of +/- 1F. For Consistent Comfort. For Use With Heat Pumps With Auxiliary Heat. Features: Easy To See Read Backlit Display With Soft-touch Button Interface Quality Temperature Control For Heat Pump With Auxiliary Heat Mercury Free Thermostat For Use With Heat Pum