The crankshafts were fitted with gears, which drove a sun gear arrangement. The rear clutch controls power to the secondary sun gear. The forward clutch controls power to the primary sun gear. In a typical application, the drive power connects to the sun gear. The Sun gear is b1/b2 and b2 has 64 teeth. In this case, the ring gear is usually fixed and the sun gear is driven. In the image, the yellow shaft carries the sun gear which is almost hidden. Their suns are bonded - in practice, both gearsets share a longer sun gear.