Control knob

A control knob is a rotary device used to provide manual input adjustments to a mechanical/electrical system when grasped and turned by a human operator, so that differing extent of knob rotation corresponds to different desired input.

Control knobs are a simpler type of input hardware and one of the most common components in control systems, and are found on all sorts of devices from taps and gas stoves to optical microscopes, potentiometers, radio tuners and digital cameras, as well as in aircraft cockpits.

[1] A control knob works by turning a shaft which connects to the component which produces the actual input.

Common control components used include potentiometers, variable capacitors, and rotary switches.

The use of a pointer on the knob in conjunction with a scale assists in producing repeatable settings; in other cases there may be a dial or other indicator which is either mechanically linked the knob's rotation (as in many older radio tuners) or which reports the behavior being controlled.