Belt and Gear Drive

Input is the green shaft of two green pulleys (Dg dia.) rotating regularly with Vg velocity.
Output is the pink crank of Vp velocity.
The blue block of a blue small pulley (Db dia.) and a gear of Zb teeth idly rotates on the pink crank.
The yellow block of a yellow large pulley (Dy dia.) and a gear of Zy teeth idly rotates on the pink crank.
The orange gear of Zo teeth idly rotates on a pin of the pink crank.
Vp = Vg (Dg/(Dy.Db)).((Db.Zy – Dy.Zb)/(Zy + Zb))
This case:
Dy = 3.Dg + 3.Db
Zo = 20; Zb = 40; Zy = 80
Vp = 9.Vg
Vp can be very small by choosing appropriate pulley diameters and gear tooth numbers in order to decrease value of ((Db.Zy – Dy.Zb).