Class 9 Electrical and electronic apparatus in general, electric apparatus for varying the current intensity in a controlled circuit, dependant upon variations of radiant energy affecting a controlled circuit, said apparatus adapted for use with industrial equipment including signals, safety appliances, counters, combustion supervisors; timing and programming controls for fluid fuel burners, furnaces, and systems, and accessories used therewith; boiler water level and boiler feedwater controls, including low water safety cut-out systems; photoelectric and other electronically operated flame failure systems for such burners and furnaces