The features of a gyroscope and a universal joint are combined to produce a constant velocity drive between two skew shafts. The essential feature of this assembly is that the two shafts are connected to a ring, one from the inside and one from the outside. The connections are made in such a way that the shafts can rotate relative to the ring. The rotating axes of the shafts on the rings are perpendicular.
Note that the inner yellow ring and the outer green ring are shown only to illustrate the relationship to the gyroscope. The mechanism is operable without them.