Actuation is the equipment assembled to a valve, damper or other device that provides the power to open or close the valve, as well as report on its current postion. The basic types of operators are Electric, Pneumatic, and Electro-hydraulic. Actuators can provide linear motion, or provide, 90 degree rotation for 1/4 turn valves. They can also be multi-turn for longer strokes. Accessories such as positioners and limit switches can be combined for control and notification of valve status..