The blue pin slides on flat portions of the red lever and of the yellow slider.
Input: the red oscillate lever.
Output: the yellow slider.
Dimension condition: d = 0.34b
d: center distance between two revolution joints of the red and green levers.
b: center distance between the blue pin and revolution joint of the green lever.
The slider velocity is constant if the red lever osciltates with a constant velocity in the range +/- 30 degrees (angle α) around the line connecting two revolution joints of the red and green levers.
Otherwise stated, the displacement relation between the red lever and the yellow slider is linear. This feature can be used for length measuring tools where the indicator graduation must be even.
In case without the green bar (the red bar has a pin that contact with the flat portion of the yellow slider) the slider velocity alters (cosine function of angle α).
Advantage over rack-pinion drive: high precision of transmission at low manufacture cost.