It had been popular from the early 20th century for its ease of use as compared to completely handbook gearboxes of that time.  Compound Planetary Gearset This automatic transmission takes advantage of a set of gears, called a compound planetary gearset, that looks like one planetary gearset but really behaves https://hectoracayv.bloggazza.com/32826003/not-known-details-about-gearbox-auto