Fisher GS 220 is a 4 part control valve for automated process control applications. It is used for applications requiring a high level of accuracy and repeatability. The control valve consists of four main components: actuator, positioner, valve body and valve accessories. The actuator is a pneumatic diaphragm or linear motor unit that converts the pressure signal from the positioner into a valve stem movement, which then adjusts the flow rate or position of the valve plug. The positioner accepts the commanded signal from the control system to precisely position the valve plug in response to process conditions. The valve body houses the shutoff portion of the valve, which can be a single or double guided valve plug or an open loop globe-style valve. The valve accessories include such components as pressure differential transmitters, lever adapters, accessories for mounting, and stem extensions.