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A rectangle with a line through it, marking a fuse.
Also known as: Fuse schematic symbol, Rectangle with a line, Cartridge fuse symbol
A fuse is drawn as a rectangle with a line running through it lengthwise — the body and the wire inside that melts. It is a deliberately sacrificial component, and the symbol marks the point a circuit is designed to fail.
Marks a fuse: a component containing a conductor designed to melt and break the circuit when current exceeds a rated value.
Contexts: Electrical equipment
Draws the component literally — the rectangle is the fuse body and the line through it is the element inside that melts.
Contexts: Electrical equipment
Marks the point at which a circuit is intended to fail, which makes it a safety feature rather than a fault; replacing a fuse with a higher-rated one defeats the protection it exists to provide.
Contexts: Electrical equipment
Has several drawn forms in use, including a plain rectangle, a rectangle with a line, and an S-shaped curve within a rectangle, which vary by convention and by era.
No single canonical drawing is asserted here.
Contexts: Electrical equipment
Is drawn two different ways by two different standards. The international form defined by the IEC is a rectangle with a line running through it from lead to lead; the form defined by the American ANSI and IEEE standards is an S-shaped or looped line between two terminals, and in older drawings a small rectangle with a wavy line. Neither is a mistake and neither is old-fashioned — a reader meeting an unfamiliar drawing of a familiar component is usually looking at the other continent's standard rather than at an error.
Contexts: Technical drawing, Electrical equipment
Is annotated with its rating and its speed, and both matter. A fuse marked T is time-lag and tolerates the surge a motor or a transformer draws at switch-on; one marked F is quick-acting and protects semiconductors. Substituting one for the other passes inspection and defeats the protection.
Contexts: Electrical equipment
Related forms that are not treated as separate canonical symbols — see our variant rules.
IEC rectangle-and-line form
A plain rectangle with a straight line through it, the international form.
ANSI looped form
An S-curve or loop between two terminals, the form used in American schematics.
A narrow rectangle standing in a wire, with a straight line running through it from one short end to the other.
Under IEC practice the resistor is also a plain rectangle in a wire; the fuse's internal line is the distinguishing mark.