Rotary switch general construction includes either open or enclosed frame. In open frame switches the moving parts are clearly visible. In enclosed frame switches the parts are not visible. The design considerations for each are: Open Frame switches offer more flexibility for contact configurations. Open Frame switches have a bifurcated wiping or self cleaning contact system ensuring reliable operation. Open frame switches can have sections sold separately. Enclosed Frame offers more protection from dust and contamination. Enclosed frame switches are generally less expensive and more compact.