Ideal for Spot lights and all other heaters up to 600 watts. Controls the temperature by increasing or decreasing the electrical current to give an even temperature output, ie. the heater will give out less heat when less heat is required (will cause light to dim) rather than switching off altogether as with simple on off type thermostats. With the added function to reduce night time temperatures. This is achieved by connecting a simple plug in type timer to the secondary input of the thermostat which triggers the required (set via a second control dial) night time drop in temperature.