It had been initially released in 1939 for vehicles. It contains the fluid coupling and 3 planetary gears. They collectively make three ahead and 1 reverse velocity. There isn't a clutch for engagement and disengagement through the engine. Most transmissions in contemporary autos use synchromesh to synchronise the speeds https://gearbox31863.angelinsblog.com/32961702/indicators-on-gearbox-you-should-know