A runtime system of an industrial controller has a running level model which has a plurality of running levels of different types with different priority. The sensor comprises a body member having an aperture therethrough. The master generates signals used to control vertical retrace and buffer swapping for itself and the slaves. standing on one leg for a selected test period. Some racks are continuous, curvilinear, and are made from rods or heavy gauge wire. It also allows a combination of the modes controlled by the mode selector and the separate spray mode.