English: A conceptualized model of a simple electro-mechanical actuator. The system converts rotary motion (in the form of an electric motor) to linear motion. When an electrical source is applied to the motor, the threaded shaft is driven and the nut rides up and down the shaft in the corresponding direction. This action provides an extension and retraction capability for tasks requiring a linear displacement. Note that in this example the nut and red tube do not rotate, merely "ride" the threads on the spinning shaft up and down.