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A circle with a cross inside it, marking a lamp or indicator.
Also known as: Bulb symbol, Indicator lamp symbol, Circle with an X, Light symbol
A circle crossed by two diagonal lines marks a lamp. The cross has no physical counterpart in the component — unlike most schematic symbols it depicts nothing, and is simply a mark chosen to be unmistakable at small size.
Marks a lamp or indicator light in a circuit: a component that produces light when current passes through it.
Contexts: Electrical equipment
Does not depict the component. Unlike the capacitor's plates or the inductor's coil, the cross inside the circle stands for nothing physical and was chosen for legibility at small size.
Contexts: Electrical equipment
Appears in several forms across conventions — a circle with a diagonal cross, a circle with an upright cross, or a circle with a wavy line for a signal lamp — which are not fully interchangeable between standards.
No single canonical drawing is asserted here.
Contexts: Electrical equipment
Distinguishes an illuminating lamp from an indicator by what is inside the circle. A circle with a cross through it is the general lamp; a circle with rays drawn outward is a signal or indicator lamp, whose job is to be looked at rather than to light a room. On a control panel the second is what a reader is almost always seeing.
Contexts: Technical drawing, Electrical equipment
Related forms that are not treated as separate canonical symbols — see our variant rules.
Signal lamp
A circle with short rays radiating from it, marking an indicator whose purpose is to show a state.
A plain circle with two straight lines crossing at its centre, drawn corner to corner so the cross touches the circle at four points.