Deep fryers are used for cooking many fast foods and today commercial fryers can come with an array of different features. They obviously have a basket to raise the food out of the oil when the cooking is completed, but they can have all sorts of other features too. Some have an automatic device to lower the basket into the oil when it is ready and lift it out again when cooking has ended.
There are many companies like Sitform that provide fryers with the latest features like audible alarm, and mechanical or electronic temperature controls. Some have ventilation systems to reduce the smell of frying, oil filters to extend the useful life of the oil and systems to prevent food crumbs being overcooked.
Many commercial fryers are highly energy efficient, especially those using convection heating or infra-red heating, but they can be expensive to purchase in the first place. The more common fryers are either electric or gas operated.
The materials used for commercial fryers are usually stainless steel or mild steel. Stainless steel is preferable because it is not likely to corrode or stain as mild steel can, and it doesn't expand under the heat. Many of the latest commercial fryers have electronic temperature controls.