We'd like to use analytics cookies to understand which symbols people look up, so we know what to research next. They are not used for advertising and we set none of them unless you say yes. What we store.
Two coils facing each other across parallel lines, marking a transformer.
Also known as: Transformer schematic symbol, Two coils symbol, Isolation transformer symbol
Two coils drawn facing each other across a pair of lines mark a transformer. The lines are the shared iron core, and their presence is the point: the two circuits are coupled magnetically without being connected electrically.
Marks a transformer: two coils sharing a magnetic core, transferring alternating current between circuits and usually changing the voltage.
Contexts: Electrical equipment
Shows the two windings as inductor coils facing each other, with the pair of parallel lines between them representing the shared iron core.
Contexts: Electrical equipment
Shows that the two sides are not electrically connected — the gap between the coils is the isolation, which is the property safety-critical transformers are fitted for.
Contexts: Electrical equipment
Carries small dots beside one end of each winding where the relative phase matters, indicating which terminals rise in voltage together.
Contexts: Electrical equipment
Marks winding sense with a dot at one end of each coil. The dots say which terminals rise in voltage together; swapping them inverts the output. In a power supply that is a nuisance, in a push-pull amplifier or a switching converter it is the difference between working and not.
Contexts: Technical drawing, Electrical equipment
Is drawn two different ways by two different standards. The international form defined by the IEC is two coils drawn as humps facing a pair of core lines; the form defined by the American ANSI and IEEE standards is the same pair of coils, conventionally drawn as spirals. 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
Related forms that are not treated as separate canonical symbols — see our variant rules.
Air-cored transformer
The two windings with no core lines between them, used at radio frequencies where an iron core would be lossy.
Centre-tapped secondary
A third connection taken from the middle of the output winding, drawn as a lead leaving the coil between its ends. The basis of the classic full-wave rectifier.
Two sets of semicircular humps facing each other, separated by two short parallel vertical lines running between them.
Drawn as two inductor coils sharing a core.