Input: pink gear shaft.
Its number of remained teeth Z1c = 9
Its number of teeth (teeth-completed) Z1 = 20
Its number of cut-off teeth Z1f = Z1 – Z1c = 11
The blue gear (teeth-completed) has Z2 = 20 teeth.
When the pink makes 1 revolution, the blue makes 1/2 revolution.
Glass disk is fixed to the blue shaft. Orange circular slider is fixed to the disk by red screw (pushing on bottom of the dovetail groove). Violet slider reciprocates with dwells at both ends of its stroke. It is possible to get dwell at middle of the stroke by adjusting position of the circular slider on the disk.