Panasonic st4 safety beam sensor system panasonic st4 c11 this unit is the controller for the st4 safety beam sensor system the controller has the functionality to support productivity as well as making it easier to design safety circuits a dual pnp or dual npn output gives versatile operation and up to six sets can be serially connected whilst still giving interference prevention the st4 is a safety light beam system that is extremely effective in both wide areas and narrow spaces the f