{"schemaVersion":1,"slug":"iec-timing-relay-form-normally-open-contact-instant","name":"IEC timing-relay form: normally open contact (instant)","kind":"symbol","abbreviation":"KT","aliases":["HTD21I","VTD21I","timing-relay form Normally Open Contact (Instant)"],"category":"control-circuits","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"Timing-relay form form: Normally Open Contact (Instant).","description":["A timing relay separates the initiating signal from the later change of an output contact. The contact state, delayed transition and reset condition are independent: a timer may have immediate contacts alongside delayed contacts under the same device tag. This entry identifies the normally open contact (instant) form in the publisher's IEC-context family.","A control sequence may start an auxiliary before enabling the main load, or keep a fan running after a stop request. Trace supply, trigger and output separately, then draw a timing chart that includes what happens when the trigger ends before a delay has elapsed. The normally-open designation starts with a non-conducting output or open contact in the documented reference condition; operation changes that state. The output contact follows the initiating condition without the intentional delay used by the timer outputs. Its linkage to the timer still needs the same device tag.","The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout."],"readingNotes":["The normally-open designation starts with a non-conducting output or open contact in the documented reference condition; operation changes that state.","The output contact follows the initiating condition without the intentional delay used by the timer outputs. Its linkage to the timer still needs the same device tag.","The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout."],"drawingChecklist":["Identify the initiating supply or control signal.","Label delayed and immediate output transitions separately.","Reference timing settings, reset conditions and the device timing chart."],"distinction":"This entry adds the normally open contact (instant) detail to the broader timing-relay form family. The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout.","facts":[{"label":"Drawing form","value":"Normally Open Contact (Instant)"},{"label":"Public vendor block names","value":"HTD21I / VTD21I. Autodesk identifiers, not standards database IDs."},{"label":"Drawing purpose","value":"timing-relay form"},{"label":"Graphic scope","value":"Independently authored educational illustration; not certified standard geometry, a terminal pinout or a product footprint."}],"references":[{"sourceId":"pub-symbol-timers","relevance":"Public Time Delay Relays table explicitly lists HTD21I / VTD21I with this operating or connection form. Vendor graphics are linked, not copied."}],"related":["on-delay-timer-relay","off-delay-timer-relay","relay-coil"],"artwork":"s28-iec-timing-relay-form-normally-open-contact-instant","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEC","form":"Normally Open Contact (Instant)","reference":"Autodesk IEC-60617 Symbol Preview: Time Delay Relays, HTD21I / VTD21I. This identifies the publisher's library context; exact IEC graphics and database identities are not asserted."},"plainEnglish":{"title":"What does IEC timing-relay form: normally open contact (instant) mean?","introduction":"A timing relay separates the initiating signal from the later change of an output contact. The contact state, delayed transition and reset condition are independent: a timer may have immediate contacts alongside delayed contacts under the same device tag. This entry identifies the normally open contact (instant) form in the publisher's IEC-context family.","example":"A control sequence may start an auxiliary before enabling the main load, or keep a fan running after a stop request. Trace supply, trigger and output separately, then draw a timing chart that includes what happens when the trigger ends before a delay has elapsed. The normally-open designation starts with a non-conducting output or open contact in the documented reference condition; operation changes that state. The output contact follows the initiating condition without the intentional delay used by the timer outputs. Its linkage to the timer still needs the same device tag.","drawings":"The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout.","terms":[{"name":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."},{"name":"Coil","meaning":"A wound conductor that can produce a magnetic field when energised."},{"name":"Terminal","meaning":"An identified point where a conductor connects."}],"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":"AutoCAD Electrical: Time-delay relays","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-DA927086-EEAF-48CB-B9B1-634A4B48C8C7.htm"}],"detail":"Timing-relay form form: Normally Open Contact (Instant). This entry adds the normally open contact (instant) detail to the broader timing-relay form family. The symbol does not supply the time setting, retriggering rule or power-loss behaviour. A three-terminal timing form also needs its actual manufacturer terminal mapping; the vendor name alone does not define a universal pinout.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/iec-timing-relay-form-normally-open-contact-instant","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/iec-timing-relay-form-normally-open-contact-instant.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pub-symbol-timers","title":"AutoCAD Electrical: Time-delay relays","publisher":"Autodesk","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-DA927086-EEAF-48CB-B9B1-634A4B48C8C7.htm","type":"cad-reference","scope":"Public vendor catalogue naming and functional variants. Vendor block names are not IEC identifiers. Linked for reference; no graphics or CAD files are redistributed.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public Time Delay Relays table explicitly lists HTD21I / VTD21I with this operating or connection form. Vendor graphics are linked, not copied."}]}