Raymarine Wireless Mast Rotation Transmitter [T221] Anchoring & Docking Cleats Freedom HF 1800 inverter charger is CEM 96311 Freedom HF 1800 inverter charger is designed to run entertainment systems and small appliances in smaller boats Tent Floor Area: 10 ft x 9 ft This unique transmitter compensates for the movement of a rotating mast to ensure that you get the most accurate wind readings at all times Operating as a wireless device on a Micronet network the Mast Rotation Transmitter compares compass information from the boat with its own information and corrects the wind angle coming from a standard wind transmitter at the mast head