Fuse boxes and outdoor electrical meters are two examples of metal boxes that are essential to the safe and effective operation of all electronic equipment in homes. Businesses also depend on metal box-enclosed electrical equipment to keep their operations supplied with power. Especially in industrial contexts, businesses cannot do without electrical enclosures; they keep sensitive electronic components from becoming contaminated with dust and debris. They also reduce the chances of components becoming damaged from accidental impact with machinery or workers. Metal box enclosures can be large enough to house entire electrical panels; such enclosures can be seen at many intersections where computerized traffic control software manages the tempo of traffic signals. They can also be as small as simple wall-mounts; many light switches are composed of partial metal boxes covered with a plastic plate for aesthetic and safety purposes.The word "box" evokes rectangular and square shapes, though the words "metal box" can be used to describe metal enclosures with more than just six faces. Also, especially in the case of hand-held examples, many metal boxes feature rounded edges and corners. Depending on a given metal box's application, it may be composed of nothing but a single layer of metal, or it can feature several layers of metal insulated with another material and fitted with interference-resistant shielding. Standardization organizations have established ratings to indicate to professionals what kinds of boxes are suitable for certain purposes. Among the more prominent of these organizations is the National Electrical Manufacturers Association (NEMA), which rates metal enclosures that are used to house electronics. NEMA's rating scale ranges from ratings for products that provide basic protection from dust to products that can be submerged in oil. Other agencies like the International Electrotechnical Commission also produce rating systems that help professionals choose metal boxes that are appropriate for their purposes. While metal boxes may not seem like they merit the scrutiny of international commissions for standardization, the importance of those efforts is clear in recognition of the reality that metal boxes house computers that regulate traffic flow, the hardware that keeps telecommunication lines operational and many other kinds of important equipment.