Input: pink gear shaft rotating one way (clockwise) at Vi velocity.
Output: green gear shaft that can rotate two ways subject to axial position of the pink shaft.
When the pink gear is in mesh with yellows gears, the output rotates counterclockwise at velocity V1
V1 = Vi/(Zg/Zp)
Zg and Zp are tooth numbers of green and pink gears respectively.
In this video Zg = 60; Zp = 20; V1 = Vi/3
When the pink gear is in mesh with green pins fixed to the green gear, the output rotates together with the input at velocity V2 = Vi.
A pin, which can slide in the hole of the middle bearing to fix the pink shaft axially after adjustment, is not shown.