Lever 1, turning about fixed axis A, has slot a of special shape which actuates pin 3. Pin 3 slides along a guide of link 2. Link 2 is connected by turning pair d to lever 1. When lever 1 is turned, link 2 is shifted from one extreme position to the other. Each extreme position corresponds to a position of lever 1 up against one of the stops b and a position of link 2 up against one of the stops c. Spring 4 applies force to hold the device in its extreme
positions.
$350$SL,SE$