Input: green wheel.
Output: yellow wheel (or vice versa).
The wheels have Archimedean grooves of the same radial distance between successive turnings T and of opposite spiral directions.
Distance between two red pins of blue slider is equal to the one between two bearings of the wheels.
The two wheels rotate in opposite directions with the same speed (transmission ratio i = -1), like in a crossed belt drive but only for limited revolutions.
If T is not the same for the two wheels i differs from -1.