{"schemaVersion":1,"slug":"iec-open-collector-buffer","name":"IEC open-collector buffer (rectangular form)","kind":"symbol","abbreviation":"1","aliases":["IEC open-drain buffer","L-type open-circuit output buffer","buffer with open-collector output"],"category":"logic-signals","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"IEC buffer with an underlined diamond at the output, showing an open-collector or open-drain stage.","description":["The underlined diamond inside the outline marks an output that can pull to a low level but needs an external pull-up to produce a high level. TI's public explanation describes this as suitable for a positive-logic wired-AND connection. The 1 qualifier makes the element non-inverting overall.","Open-collector outputs are used for shared alarm lines, level shifting to a higher pull-up voltage, and driving small relays or indicator lamps. The pull-up resistor or load must be shown on the drawing, together with its supply, because the element cannot produce a high level by itself.","The symbol does not state the maximum sink current or the maximum voltage the output may be pulled to. Those limits are device data and govern whether a relay coil or lamp can be connected directly."],"readingNotes":["Find the pull-up resistor or load and its supply rail.","Check whether several outputs are wired together."],"drawingChecklist":["Show the underlined diamond next to the output.","Draw the pull-up and label its supply.","Note the sink current and voltage limits where a load is driven directly."],"distinction":"An overlined diamond is the H-type open-emitter output, which sources current and needs a pull-down.","facts":[{"label":"Output qualifier","value":"Diamond with underline (L-type open circuit)"},{"label":"External part required","value":"Pull-up resistor or load"},{"label":"Wired connection","value":"Positive-logic wired-AND"},{"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 the open-collector output qualifier and its wired-AND capability."},{"sourceId":"pub-electronics-ti-ls07","relevance":"Manufacturer open-collector buffer documentation."}],"related":["open-collector-buffer","iec-open-circuit-output-l-type","ansi-wired-and-connection"],"artwork":"s28-iec-open-collector-buffer","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEC","form":"1 element with the underlined-diamond open-circuit (L-type) output 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":"open-collector-buffer"},"plainEnglish":{"title":"What does IEC open-collector buffer (rectangular form) mean?","introduction":"The underlined diamond inside the outline marks an output that can pull to a low level but needs an external pull-up to produce a high level. TI's public explanation describes this as suitable for a positive-logic wired-AND connection. The 1 additional drawing mark makes the element non-inverting overall.","example":"Open-collector outputs are used for shared alarm lines, level shifting to a higher pull-up voltage, and driving small relays or indicator lamps. The pull-up resistor or load must be shown on the drawing, together with its supply, because the element cannot produce a high level by itself.","drawings":"The symbol does not state the maximum sink current or the maximum voltage the output may be pulled to. Those limits are device data and govern whether a relay coil or lamp can be connected directly.","terms":[{"name":"Coil","meaning":"A wound conductor that can produce a magnetic field when energised."},{"name":"Terminal","meaning":"An identified point where a conductor connects."},{"name":"Signal","meaning":"Electrical information passed between devices, rather than necessarily the main power supply."}],"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":"SN74LS07 — open-collector output buffers","url":"https://www.ti.com/lit/ds/symlink/sn74ls07.pdf"}],"detail":"IEC buffer with an underlined diamond at the output, showing an open-collector or open-drain stage. An overlined diamond is the H-type open-emitter output, which sources current and needs a pull-down.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/iec-open-collector-buffer","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/iec-open-collector-buffer.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 the open-collector output qualifier and its wired-AND capability."},{"id":"pub-electronics-ti-ls07","title":"SN74LS07 — open-collector output buffers","publisher":"Texas Instruments","url":"https://www.ti.com/lit/ds/symlink/sn74ls07.pdf","type":"manufacturer","scope":"Public device-function and terminal documentation used as an example of open-collector output buffers. 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 open-collector buffer documentation."}]}