Cam 1 rotates about fixed axis A and its working surface is composed of concentric circular arcs a and b of different radii. Follower 4 oscillates about fixed axis B and carries roller 3 which rolls along the surface of cam 1. Compression spring 2 holds roller 3 in contact with cam 1. When cam 1 rotates, contacts d and e are periodically closed and opened. Proper closing of the contacts is ensured by spring 5 because contact d can turn slightly about axis C.
$3100$SmC,SE$