This report entails the design process and development of a rotational ring system that must
serve as an user interface for an existing system, the ADEPTH. The goal of the rotational ring is to allow a surgeon to make selections in the user interface system. After careful consideration of the provided list of requirements, it was decided to use changes in magnetic fields, sensed by a Hall sensor. This Hall sensor detects whether an external ring was rotated to the left or to the right. The inside of the ring contains six samarium-cobalt magnets, chosen for their extreme resistance to demagnetisation at high temperatures. This was a consideration, because the magnets have to undergo repeated cycles of sterilisation as hot as 134◦ C. After iterated prototype testing, a final working prototype has been developed, which can communicate wirelessly with the user interface system and send ’left’ & ’right’ commands. This final prototype is watertight and low power, which satisfies two of the most desired requirements.