Lever 1, turning about fixed axis A , has lug a . Levers 2 and 3, linked together by spring 4, have projections b . When lever 1 is turned to either side, lug a engages projection b of lever 2 or 3 (lever 2 as illustrated). This lever i s turned about fixed axis B , forcing projection b of the other lever against stop d and compressing spring 4 . When lever 1 is released, it is returned by spring 4 to its initial (central) position.
$145$SL,L$