{"schemaVersion":1,"slug":"iec-xor-gate","name":"IEC exclusive-OR gate (rectangular form)","kind":"symbol","abbreviation":"=1","aliases":["IEC XOR element","equals-one gate","rectangular exclusive-OR"],"category":"logic-signals","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"Rectangular element marked =1: the output is active when one and only one input is active.","description":["The =1 qualifier defines an exclusive-OR in the strict IEC sense: exactly one input must be active for the output to be active. For a two-input element this matches the familiar XOR truth table. For more than two inputs it is not the same as a cascaded parity function, which IEC writes as 2k+1.","On control drawings the =1 element appears in discrepancy checks, such as comparing a commanded position with a feedback contact, and in change-detection logic. The drafter should keep the element at two inputs unless the one-and-only-one meaning is truly intended.","The qualifier does not indicate timing tolerance. Discrepancy logic normally needs a delay element after the =1 box so that the alarm ignores normal transit time; that delay is a separate symbol."],"readingNotes":["For three or more inputs, read =1 as exactly one active, not odd parity.","Look for a following delay element in discrepancy logic."],"drawingChecklist":["Use =1 only where exactly-one behaviour is intended.","Use 2k+1 instead when odd parity is meant.","Show any discrepancy delay as its own element."],"distinction":"The 2k+1 odd-parity element gives the same result for two inputs but a different result for three or more.","facts":[{"label":"Qualifier","value":"=1 (one and only one input active)"},{"label":"Multi-input caution","value":"Not equivalent to odd parity above two inputs"},{"label":"Artwork scope","value":"Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic"}],"references":[{"sourceId":"s28-ti-ieee91-logic-symbols","relevance":"Defines =1 and distinguishes it from the 2k+1 parity qualifier."},{"sourceId":"pub-electronics-ti-hc86","relevance":"Manufacturer exclusive-OR documentation."}],"related":["logic-xor-gate","iec-odd-parity-element","iec-xnor-gate"],"artwork":"s28-iec-xor-gate","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEC","form":"Rectangular outline with the =1 qualifier","reference":"Qualifying-symbol and dependency conventions as explained in TI's public overview of IEEE Std 91-1984, which incorporates IEC 617-12 work. Independent educational drawing; not certified IEC geometry or an IEC database identifier. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.","counterpart":"logic-xor-gate"},"plainEnglish":{"title":"What does IEC exclusive-OR gate (rectangular form) mean?","introduction":"The =1 additional drawing mark defines an exclusive-OR in the strict IEC sense: exactly one input must be active for the output to be active. For a two-input element this matches the familiar XOR truth table. For more than two inputs it is not the same as a cascaded parity function, which IEC writes as 2k+1.","example":"On control drawings the =1 element appears in discrepancy checks, such as comparing a commanded position with a feedback contact, and in change-detection logic. The drafter should keep the element at two inputs unless the one-and-only-one meaning is truly intended.","drawings":"The additional drawing mark does not indicate timing tolerance. Discrepancy logic normally needs a delay element after the =1 box so that the alarm ignores normal transit time; that delay is a separate symbol.","terms":[{"name":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."},{"name":"Signal","meaning":"Electrical information passed between devices, rather than necessarily the main power supply."},{"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":"Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)","url":"https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf"},{"label":"SN74HC86 — XOR gate logic","url":"https://www.ti.com/lit/ds/symlink/sn74hc86.pdf"}],"detail":"Rectangular element marked =1: the output is active when one and only one input is active. The 2k+1 odd-parity element gives the same result for two inputs but a different result for three or more.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/iec-xor-gate","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/iec-xor-gate.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"s28-ti-ieee91-logic-symbols","title":"Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)","publisher":"Texas Instruments","url":"https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf","type":"manufacturer","scope":"Public explanation of rectangular logic symbols, general qualifiers, input and output qualifiers, dependency notation, bistable elements and coders, consistent with IEC 617-12 work.","checkedOn":"2026-10-28","reuse":"link-only","relevance":"Defines =1 and distinguishes it from the 2k+1 parity qualifier."},{"id":"pub-electronics-ti-hc86","title":"SN74HC86 — XOR gate logic","publisher":"Texas Instruments","url":"https://www.ti.com/lit/ds/symlink/sn74hc86.pdf","type":"manufacturer","scope":"Public device-function and terminal documentation used as an example of xor gate logic. Example part numbers are manufacturer identifiers, not IEC/IEEE symbol IDs. Device ratings, pin numbering and availability remain in the selected product documentation.","checkedOn":"2026-10-14","reuse":"link-only","relevance":"Manufacturer exclusive-OR documentation."}]}