An illuminated electric part includes a manipulating shaft which is rotatable and is stable at least at two points. A current balancing circuit is provided that maintains a constant current demand on the eFuse voltage supply that is sufficient to blow an eFuse. The illumination elements may be modular, allowing components to be mixed and matched for different sizes of blade retractors, or may be a single integrated unit. Each of the time period indicators includes an item container. The trough and tower are of particular value in a sulphuric acid plant and a carbon dioxide capture plant. In the partially energized configurations, the poppet and check ball permit flow to and from all of the ports, and incremental changes in the internal displacement of the poppet produce incremental changes in a control pressure.