When wheel 1 rotates, p in 2, secured to the spokes of the wheel,
strikes the teeth of sprocket 5 whose axle is rig id ly mounted
on fork 3. Sprocket 5 has square a which closes contacts 4 each
time the sprocket turns one fourth of a revolution, i.e. per revolu
tion of wheel 1. Therefore, each revolution of the wheel corresponds
to one current pulse.
$4398$SmE,M$