Input: green shaft with four gears fixed on it.
Output: red shaft with pink, violet, yellow and blue gears rotating idly on it.
The gears are permanently in mesh. The orange toothed clutches has sliding key joint with the output shaft. 3 positions of each clutch are controlled by blue barrel cam. The mechanism gives 4 speeds and neutral positions.
To avoid clutch collision, the speed change must be carried out when the input shaft stops. The operation shown in this video is for the case of very slow speed.