A limit switch is an electromechanical device that consists of an actuator mechanically linked to a set of contacts. When an object comes into contact with the actuator, the device operates the contacts to make or break an electrical connection.

The limit switch then regulates the electrical circuit that controls the machine and its moving parts. These switches can be used as pilot devices for magnetic starter control circuits, allowing them to start, stop, slow down, or accelerate the functions of an electric motor.

A Mechanical limit switch is a mechanical device which can be used to determine the physical position of equipment. … Many Mechanical limit switches are the push-button variety. When the valve extension comes in contact with the limit switch, the switch depresses to complete, or turn on, the electrical circuit

The Limit Switch is a visual sign which indicates whether the valve is open or closed. The Positioner allows the valve to open to a specified angle, between 0 and 90 degrees. The Actuator is used to open and close the valve.

The limit switch is a safety control switch located on the furnace just below the plenum. If the plenum gets too hot, the limit switch shuts off the burner.