Optical and digital potentiometers and controllers. In one embodiment of the invention, a paddle slider is maintained within a housing along with a light source and sensor. The amount of light received by the sensor is a function of the position of the slider and, accordingly, a control signal output may be developed corresponding to the mechanical position of the slider. In other embodiments, light sources are caused to impinge on reflective surfaces which reflect the light through a film onto additional reflective surfaces which direct the light to a sensor. The film may be of varying optical density along the length thereof such that the amount of light received corresponds to the position of the slider, or the film may be digitally encoded such that separate light beams received by the sensor will correspond to a digital position of the slider. In another embodiment, a cylindrical digitally encoded film is rotated between a light source and sensor, thereby varying the output of the sensor. In still another embodiment, a pressure bar is maintained upon a slide and transverses a switch pad which is connected to an electronic decoding circuit. As the slide is moved, the output of the switch pad changes as a digital function of the position of the slide.