Just incase anyone else is searching for this. This is a servo switch that was built for my project for a diesel heater for a camper van/motor home. When connected up to a thermostat it acts as a diverter allowing heat to be transferred to two different areas once up to temperature . In my case I’m heating up the water using the diesel heater. Once the thermostat hits the required temperature it deactivates and makes the servo move to the other side directing the heat to the camper van/motor home. FYI It can be fully customised to fit your set up like a three way position to allow you to have both hot water and heating in your camper.