Honeywell Thermostat, T4 Pro Series, 20 to 30 VAC, 50/60 Hz Frequency, Programmability: 7 day, 5-1-1 day, 5-2 day, or Non-Programmable, Changeover: Auto, Manual, Battery, Hardwired Power Source, 1 Heat/1 Cool Conventional Systems, 2 Heat/1 Cool Heat Pumps Stages, Switch Position: HEAT-OFF-COOL-AUTO-EM HEAT (System), AUTO-ON (Fan), Relay Switch, 3.93 sq-in Display, +/-1 deg F Differential, 40 to 90 deg F Heating, 50 to 99 deg F Cooling Settings, 37 to 102 deg F Operating, to 20 to 120 deg F Shipping and Storage, 5 to 90% RH Non-Condensing Humidity, 0.5 deg C Accuracy, UWP Mounting System Mounting, White, Dimensions: 4-1/16 in L x 4-1/16 in W x 1-3/32 in D