7 day programmable thermostat, unique program for every day of the week, user option: 2 or 4 periods per day, temporary override & manual hold, keyboard lock, speed slide for easy programming, selectable Fahrenheit/Celsius setting, adjustable temperature swing differential, adjustable second stage heat offset, air filter monitor, easy view large back lit display, selectable smart recovery, easy to use, easy installation, dual powered, uses 2 "aa" alkaline batteries, not included, for use on: universal compatibility for conventional heat & a/c, for heat pumps with up to 2 stage heat/1 stage cool, 3 wire heat only hydronic systems, hot water, zone valves, & gas millivolt heaters.