Non-programmable thermostats can be set to one of two modes- 1 heating or 1 cooling- to control the temperature in a room. For use with central gas, oil, electric furnaces, a/c, millivolt or ( heat pump without aux ) Single Stage Systems. Does not work with multi-stage systems & 120/240V electric baseboard. Support a heat or cool swing set up (0.2-2 F), which will either prolong or shorten the temperature open time. The battery is easy to replace and the hidden design does not affect the thermostat appearance. (Low Battery Indicator) The font size for large screen text should be 68.5 points so that it is clearly visible from a distance of 6 meters and easy to handle. Very Suitable for Middle-Aged and Elderly People, Easy-to-read Digital 4.5 sq. in. Room Temperature Calibration Adjustment, and 5 Minute Compressor Delay Protection (Selectable on or off) Support dual powered 24VAC Power or 2 AAA Batteries, C-wire is not required. Friendly Service: 2-year Worry-Free Warranty and 24h Customer Service