Abstract: A mercury inertial transducer includes a casing which defines an essentially L-shaped cavity having a substantially horizontal lower arm and a substantially vertical ascending arm; a volume of mercury which, in the rest condition, occupies the lower arm and essentially does not occupy the ascending arm; an input electrode which penetrates the lower arm from the outside and is permanently immersed in the mercury, and a series of separate output electrodes which are spaced along the ascending arm and can be reached in succession by the mercury when it rises in the ascending arm due to an inertial force directed along the lower arm towards the ascending arm. The transducer may be incorporated in a unit including a support which can be fixed to a movable object, such as a motor vehicle, and on which the transducer is mounted so that the inclination of its lower arm to the horizontal and of its ascending arm to the vertical can be adjusted.

Abstract: A piezoelectric spark generator comprises a rolling cam of rectangular cross section, the large side of which amounts to 0.08-0.15 times the effective length of the piezoelectric cartridge and in which the angle of inclination of the diagonal exceeds by 3.degree.-6.degree. the angular stroke of the actuating lever. The small longitudinal faces of the cam rest in grooves in the cooperating blocks. The frame is a piece of sheet steel folded to U-shape. The cam protrudes to the outside through opening in the branches of the frame. A portion of the edge of each opening is shaped to provide an end stop for the actuating stroke of the actuating lever.