{"schemaVersion":1,"slug":"iec-open-circuit-output-l-type","name":"IEC open-circuit output, L-type (open collector)","kind":"symbol","abbreviation":"OC-L","aliases":["underlined diamond output","open-collector qualifier","open-drain qualifier"],"category":"logic-signals","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"Underlined diamond inside an outline: an open-circuit output that can only drive a low level.","description":["The underlined diamond marks an output, such as an NPN open collector or an N-channel open drain, that can supply a relatively low-impedance L level when on and is open when off. An external pull-up is needed. TI's public overview notes this output type supports a positive-logic wired-AND connection.","When a variant with a built-in passive pull-up exists, a further mark inside the diamond distinguishes it. Reviewing the exact qualifier tells the drafter whether an external pull-up must be added to the schematic.","The qualifier does not state the maximum pull-up voltage. Some open-drain outputs tolerate a higher pull-up rail than the device supply and some do not."],"readingNotes":["Underline below the diamond: pulls low only.","Find the external pull-up on the net."],"drawingChecklist":["Draw the diamond with its underline next to the output.","Show the pull-up resistor.","Record the permitted pull-up voltage."],"distinction":"The H-type open-circuit output has the line above the diamond and drives a high level only.","facts":[{"label":"Drives","value":"Low level only"},{"label":"Wired connection","value":"Wired-AND in positive logic"},{"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":"Describes the L-type open-circuit output qualifier and wired-AND capability."}],"related":["iec-open-circuit-output-h-type","iec-open-collector-buffer","ansi-wired-and-connection"],"artwork":"s28-iec-open-circuit-output-l-type","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEC","form":"Diamond with underline inside the outline at the output","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."},"plainEnglish":{"title":"What does IEC open-circuit output, L-type (open collector) mean?","introduction":"The underlined diamond marks an output, such as an NPN open collector or an N-channel open drain, that can supply a relatively low-impedance L level when on and is open when off. An external pull-up is needed. TI's public overview notes this output type supports a positive-logic wired-AND connection.","example":"When a variant with a built-in passive pull-up exists, a further mark inside the diamond distinguishes it. Reviewing the exact additional drawing mark tells the drafter whether an external pull-up must be added to the schematic.","drawings":"The additional drawing mark does not state the maximum pull-up voltage. Some open-drain outputs tolerate a higher pull-up rail than the device supply and some do not.","terms":[{"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."},{"name":"Rating","meaning":"A value stating the conditions for which equipment is specified."}],"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"}],"detail":"Underlined diamond inside an outline: an open-circuit output that can only drive a low level. The H-type open-circuit output has the line above the diamond and drives a high level only.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/iec-open-circuit-output-l-type","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/iec-open-circuit-output-l-type.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":"Describes the L-type open-circuit output qualifier and wired-AND capability."}]}