Handle 1, turning about fixed axis A, has latch b. Plunger 4, sliding in a fixed guide, has pin c which slides along a flat surface of handle 1. Plunger 4 is actuated by spring 3. Disk 2, turning about vertical fixed axis B, has grooves a around its circumference. Disk 2 is held in the required indexed position by handle 1 whose latch b enters the corresponding groove a of disk 2 due to the action of spring 3. When handle 1 is turned counterclockwise it releases disk 2.
$401$SL,I$