it is an infinately vairiable speed trans used in the Fendt tractors. It is a design that uses a plantary drive except the outer ring gear floats for neutral and is braked to speed up the output shaft. The braking of the ring gear is done via means of a hydraulic pump connected to it. As the flow of oil is restricted the ring slows down. The oil pressure is then used to drive a pair of hydraulic motors which are used to help drive the input shaft. Kind of like perpetual motion huhIJ Super efficient. There are several brands on the market, to date none as efficient.