In one revolution of the pink input crank, the orange output slider performs two strokes, one long and one short. At the rightest point of each stroke, the links are in toggle to get high mechanical advantage and low speed.
The violet screw and the yellow slider are for adjusting stroke position.
The mechanism is applied for cold-heading rivet machines where two consequent blows of hammer (the orange slider) are needed in one revolution of crankshaft.