Lever 1, weighted to hold it in its extreme positions, has slot a of specially designed noncircular shape and turns about fixed axis B. Pin d, in slot a, is rigidly secured to rod 2 which slides in guide e of base 3. Two shoulders b limit the travel of rod 2. Rod 2 is shifted to and held in its extreme positions by turning lever 1 about axis B.
$335$SL,SE$