Idiot light is a mildly derogatory term that refers to a simplistic method of displaying information about a system (e.g. an engine, or a piece of factory equipment). Usually found in display panels, such as an automobile dashboard, idiot lights consist of an illumination source (usually an incandescent light bulb or an LED) with an explanatory symbol or text label. An "idiot light" will only turn on after a malfunction has occurred, providing no warning in advance, nor details of the malfunction's extent afterwards.