A programmable room thermostat is both a programmer and a room thermostat, which can control most domestic gas or oil powered central heating systems including combination boilers. It allows you to select different temperatures, ‘on and off’ time periods, for different times of the day and days of the week. It works by sensing the air temperature, switching on the heating when the air temperature falls below the thermostat setting and switching it off when the set temperature been reached. E.g. “Centaur State 7” supports up to 6 different temperature settings for a 24 hour, 7 day and weekly cycle.