A cam timer or drum sequencer is an electromechanical system for controlling a sequence of events automatically. It resembles a music box with movable pins, controlling electrical switches instead of musical notes.
A 7 cam 7 contact cam timer
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path. The cam can be a simple tooth, as is used to deliver pulses of power to a steam hammer, for example, or an eccentric disc or other shape that produces a smooth reciprocating motion in the follower, which is a lever making contact with the cam. A cam timer is similar, and were widely used for electric machine control before the advent of inexpensive electronics, microcontrollers, integrated circuits, programmable logic controllers and digital control.
Fig. 2 Basic displacement diagram for a rotating cam
Fig. 3 Cam profile
Motorcycle transmission showing cylindrical cam with three followers. Each follower controls the position of a shift fork.
Key duplicating machine. The original key (mounted in the left-hand holder) acts as a linear cam to control the cut depth for the duplicate.