Valves are special fittings designed to maintain and manage the flow of gasses or liquids in tubing systems. A variety of valve types are utilized both in plumbing & automated set-ups. However, manual appliances differ from automated ones. The distinction lies in the regulation mechanism, which is actually responsible for opening or closing the valve. Automated devices utilize specialized devices called "actuators". Actuators are special mechanisms utilized for opening/closing the valve or putting the inner regulators in the appropriate position. These devices may be operated by electricity, air or liquid pressure. They also require an additional source of power.