Link 1, designed as a push button, slides in fixed guides b. It is held in its upper position by spring 6 and has head a with grooves c. Lever 5 turns about fixed axis A and has hinged links 2 which are held in the position shown in the drawing (with respect to lever 5) by flat spring 3. Spring-loaded pin 7 slides in lever 5 and contacts head e of lever 4 which is connected by turning pair B to lever 5. When button 1 is pressed, lever 5 is turned by means of links 2 about pin A and pin 7 slides along head e of lever 4 shifting the lever from one extreme position to the other. The mechanism passes by inertia through the middle neutral position and, as a result, lever 4 is shifted.
$357$SL,SE$