The tado° Extension Box acts as a communication link between the tado° Smart Thermostat & the boiler. It replaces extenal controllers, external receivers or is directly connected to the boiler. The Extension Box is powered by 230V mains connection for relays & by low voltage power supply when connected to analog or digital interfaces. For potential free relay wiring, an additional two wire power supply cable maybe required which is provided by tado° upon request. tado° provides installation instructions specific to every heating setup. Those instructions are provided as online webflow. This documentation at hand is no replacement of these instructions & is a documentation of tado° devices & features, not of the installation process itself.