{"schemaVersion":1,"slug":"ansi-three-way-switch","name":"ANSI three-way switch plan symbol","kind":"symbol","abbreviation":"S3","aliases":["S3 switch","three-way switch symbol","3-way switch"],"category":"installation-communications","drawingTypes":["GA"],"referenceFamilies":["IEEE / ANSI"],"summary":"US plan symbol S3 for a three-way switch, used in pairs to control lights from two locations.","description":["The US three-way switch is drawn as S with subscript 3. Two S3 symbols appear on the plan at different entries, connected by switch legs to the same lighting group, and the installer runs travellers between them.","Despite the name, a three-way switch has a single changeover contact. The name refers to its three terminals. The equivalent IEC term is a two-way switch. The symbol does not show traveller routing or box fill; the installer plans this from the pair."],"readingNotes":["Expect S3 symbols in pairs.","Look for S4 symbols between them on long runs."],"drawingChecklist":["Show both S3 locations.","Link to the same fixtures.","Allow for travellers in conduit fill."],"distinction":"S4 is a four-way intermediate device; S3 is the changeover switch used at the ends.","facts":[{"label":"Contact","value":"Single changeover, three terminals"},{"label":"IEC equivalent term","value":"Two-way switch"},{"label":"Artwork scope","value":"Original educational illustration; the exact ANSI or IEEE graphic and compliance are not certified"}],"references":[{"sourceId":"ieee-315","relevance":"Graphic-symbol standards context; not a source of reproduced artwork."}],"related":["iec-two-way-light-switch","ansi-four-way-switch","ansi-single-pole-switch"],"artwork":"s28-ansi-three-way-switch","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEEE / ANSI","form":"Three-way switch, S3","reference":"US architectural electrical plan practice in the ANSI Y32.9 lineage, read alongside IEEE 315 context; independently drawn, not a certified IEEE or ANSI graphic."},"plainEnglish":{"title":"What does ANSI three-way switch plan mean?","introduction":"The US three-way switch is drawn as S with subscript 3. Two S3 symbols appear on the plan at different entries, connected by switch legs to the same lighting group, and the installer runs travellers between them.","example":"Despite the name, a three-way switch has a single changeover contact. The name refers to its three terminals. The equivalent IEC term is a two-way switch. The symbol does not show traveller routing or box fill; the installer plans this from the pair.","drawings":"Expect S3 symbols in pairs. Look for S4 symbols between them on long runs. S4 is a four-way intermediate device; S3 is the changeover switch used at the ends.","terms":[{"name":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."},{"name":"Terminal","meaning":"An identified point where a conductor connects."},{"name":"Schematic","meaning":"A drawing showing function and connections rather than physical appearance."}],"diagram":"flow","steps":["Identify the device and form","Read the connections and state","Check the equipment reference"],"caption":"A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.","sources":[{"label":"IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams","url":"https://standards.ieee.org/ieee/315/515/"}],"detail":"US plan symbol S3 for a three-way switch, used in pairs to control lights from two locations. S4 is a four-way intermediate device; S3 is the changeover switch used at the ends.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/ansi-three-way-switch","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/ansi-three-way-switch.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"ieee-315","title":"IEEE/ANSI 315-1975: graphic symbols for electrical and electronics diagrams","publisher":"IEEE Standards Association","url":"https://standards.ieee.org/ieee/315/515/","type":"standard","scope":"Graphic symbols and designation letters. IEEE lists this edition as Inactive-Reserved; it is a historical reference, not a claim of current compliance.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Graphic-symbol standards context; not a source of reproduced artwork."}]}