Input: one of the two gears.
Output: the other gear. It turns at the same input velocity but in opposite direction.
Yellow runways are pivoted idly on the gears so it is easy to adjust position of the output.
In place of the pins a stretch of chain fixed to the rack base is a possible variant.
It is possible to set the mechanism to get two gears rotate in the same direction: let the pin rack to mesh with both two gears on one side.