Abstract: A modular housing structure for rotatably positioning a cam on a shaft at a predetermined position relative to a limit switch. The modular housing includes upper and lower halves which are snap-fit together by an arrangement of projections and recesses which interconnect the housing halves, and hold a limit switch and a rotating cam in a fixed position relative to one another. Additionally, each limit switch module of the invention may be snap-fit onto the top or bottom of an adjacent limit switch module such that a number of modules may conveniently and easily be aligned along a single shaft. The cam rotatably received in each module is unitarily formed of a single material, and includes an inner spring collar which is deflected slightly when a shaft is inserted through the cam.