Radio features are components of a radio that allow the user to control the sound and other settings. Knobs and DIALS are two of the most common radio features. Knobs are round, usually circular, controls that can be turned to adjust the volume or other settings. DIALS are flat, usually rectangular, controls that can be used to select a station or other settings. Both knobs and DIALS are used to adjust the sound and other settings on a radio.