Links 2, 5 and 6 turn about fixed axes A, B and C. Lever 1, subject to a constant torque, is restrained from rotation by pawl 2 which is hinged to link 3 bearing against one arm of angle lever 4. When key 5 is depressed by a sharp blow, lever 6 raises link 3 and disengages pawl 2 from lever 1. As the left end of lever 6 is raised, the horizontal arm of angle lever 4 runs against adjustable stop a. As a result, link 3 is free to descend and permit pawl 2 to re-engage lever 1. For further rotation of lever 1 it is necessary to return key 5 to i ts upper position and to depress it again. Pawl 2 is engaged either by the action of the weight of link 3 or by means of a supplementary spring.
$259$SL,SD$