A knob is a general term used from door handles to electronic items. It serves the same function of opening and closing. Where a door handle controls the opening and closing of a door, in the case of an electronic circuit it is used for controlling or switching the device on or off. Knobs come in different shapes and sizes depending on where the knob is used.

Knobs come in different forms as well. They can be a simple on/off devices or they can have integrated indicating lamps within them. Knobs are also used for controlling multipurpose processes that have to work in a sequential manner. Such knobs come with shaft attached with different connectors, insulated from each other and are connected depending on the position of the knob. Many knobs are spring operated.