{"schemaVersion":1,"slug":"changeover-contact","name":"Changeover contact","kind":"symbol","abbreviation":"CO","aliases":["Form C","SPDT","single pole double throw","transfer contact","HCR23R","VCR23R"],"category":"control-circuits","drawingTypes":["Schematic"],"referenceFamilies":["IEC","IEEE / ANSI"],"summary":"A contact arrangement switching a common connection between two contact paths.","description":["A changeover contact connects a common terminal to one of two alternative contact paths according to its operating state. Form C and SPDT are terms commonly encountered for this arrangement. The actual terminal numbering and transfer behaviour come from the selected device.","The schematic should make the common terminal and normal state clear. A mirrored or differently oriented drawing can retain the same logical arrangement, but terminal associations must not be inferred from appearance alone."],"readingNotes":["Locate the common terminal and determine the path shown in the defined normal state.","Use device data to identify transfer timing and any special overlap behaviour."],"drawingChecklist":["Identify the common terminal.","Link both switched paths to the parent device.","Keep terminal identifiers consistent with wiring documentation."],"distinction":"Two unrelated NO/NC contacts are not automatically one changeover contact. Confirm whether they share a common connection and operating mechanism.","facts":[{"label":"Connections","value":"Common and two alternative paths"},{"label":"Alternative terms","value":"Form C; SPDT"},{"label":"Transfer characteristics","value":"Device-specific"},{"label":"Public Autodesk reference names","value":"HCR23R, VCR23R (vendor identifiers, not IEC symbol IDs)"}],"references":[{"sourceId":"autodesk-contacts","relevance":"Public Form C relay contact variants."}],"related":["normally-open-contact","normally-closed-contact","selector-switch","relay-coil"],"artwork":"changeover","publishedOn":"2026-10-13","updatedOn":"2026-10-13","provenance":"independent-public-research","url":"https://eloragrid.ai/symbols/changeover-contact","illustration":{"url":"https://eloragrid.ai/library/illustrations/changeover-contact.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"autodesk-contacts","title":"Relays and contacts: public symbol reference","publisher":"Autodesk","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-011C62B8-9EC8-485C-B47D-B22A3F7B7574.htm","type":"cad-reference","scope":"Normally open, normally closed and changeover contacts, relay coils and latching relay variants.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public Form C relay contact variants."}]}