Input: green shaft with two green gears fixed on it.
Output: red shaft with yellow and pink gears rotating idly on it.
The gears are permanently in mesh. The orange toothed clutch has sliding key joint with the output shaft. The clutch’s 3 positions are controlled by a rack-pinion drive.
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.