{"schemaVersion":1,"slug":"trapped-key-transfer-permissive","name":"Trapped-key transfer permissive","kind":"symbol","abbreviation":"TTP","aliases":["Switchgear interlocking functions","switchgear Switchgear interlocking functions","switchgear","Switchgear","Key availability","Dependent operation permission"],"category":"control-circuits","drawingTypes":["Schematic"],"referenceFamilies":["Manufacturer"],"summary":"Represents the required transfer of a key between equipment to enforce an operating dependency.","description":["Represents the required transfer of a key between equipment to enforce an operating dependency. An interlocking function permits or blocks an operation according to the positions and conditions of related equipment. Electrical, mechanical and trapped-key interlocks implement different parts of a coordinated operating philosophy.","In a switchgear feeder panel, a control diagram can prevent an incompatible combination of breaker, disconnector and earthing-switch positions. The physical equipment documents determine which restrictions are mechanically enforced. For this reference, the drawing identifies “Key availability” at the input and “Dependent operation permission” at the output. Key sequence and electrical state are different evidence.","Identify each initiating position, the action being blocked and the consequence of missing feedback. An illustrative logic diagram must not be treated as an operating procedure or proof of a complete safety system. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation."],"readingNotes":["Start at the named input: Key availability. Identify its source device or document and the state represented on the drawing.","Follow the named output: Dependent operation permission. Cross-reference its destination and separate the command from confirmation that the equipment responded.","Key sequence and electrical state are different evidence.","Identify each initiating position, the action being blocked and the consequence of missing feedback. An illustrative logic diagram must not be treated as an operating procedure or proof of a complete safety system."],"drawingChecklist":["Label the source and connection reference for key availability.","Identify the destination and defined state of dependent operation permission.","Record the equipment or control-document revision supporting this functional block.","Check this application limit in the project design: Key sequence and electrical state are different evidence."],"distinction":"Key sequence and electrical state are different evidence. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.","facts":[{"label":"Representation","value":"Functional block"},{"label":"Installation focus","value":"Switchgear"},{"label":"Input / boundary","value":"Key availability"},{"label":"Output / connection","value":"Dependent operation permission"},{"label":"Lookup label","value":"TTP is a library lookup label, not a standard device designation."}],"references":[{"sourceId":"pi26-masterclad","relevance":"Public technical context for switchgear interlocking functions. Breaker control, mechanism, position contacts, racking interlocks and test interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation."}],"related":["iec-mechanical-interlock-between-devices","earthing-switch","dual-incomer-parallel-closing-interlock"],"artwork":"pi26-trapped-key-transfer-permissive","publishedOn":"2026-11-03","updatedOn":"2026-11-03","provenance":"independent-public-research","representation":{"type":"functional-block","focus":"switchgear","family":"interlocks","input":"Key availability","output":"Dependent operation permission"},"plainEnglish":{"title":"What this block does","introduction":"Represents the required transfer of a key between equipment to enforce an operating dependency.","example":"In a switchgear feeder panel, a control diagram can prevent an incompatible combination of breaker, disconnector and earthing-switch positions. The physical equipment documents determine which restrictions are mechanically enforced. For this reference, the drawing identifies “Key availability” at the input and “Dependent operation permission” at the output. Key sequence and electrical state are different evidence.","drawings":"Start at the named input: Key availability. Identify its source device or document and the state represented on the drawing. Follow the named output: Dependent operation permission. Cross-reference its destination and separate the command from confirmation that the equipment responded.","terms":[{"name":"Input","meaning":"Key availability"},{"name":"Output","meaning":"Dependent operation permission"},{"name":"Application reference","meaning":"An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections."}],"diagram":"flow","steps":["Key availability","TTP","Dependent operation permission"],"caption":"A reading guide. The entry's original illustration and input/output facts describe this application.","sources":[{"label":"Masterclad medium-voltage switchgear: circuit-breaker section interlocks","url":"https://productinfo.se.com/masterclad_mv_switchgear_ib/6055-30-masterclad-15kv-mv-switchgear-ib/English/6055-30%20Masterclad%20MV%20Switchgear%20Indoor%20%28bookmap%29_DD00646805.xml/%24/Section6-CircuitBreakerSectionInter-58DD6EC7"}],"profileId":"power-installation-interlocks"},"url":"https://eloragrid.ai/symbols/trapped-key-transfer-permissive","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/trapped-key-transfer-permissive.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pi26-masterclad","publisher":"Schneider Electric","title":"Masterclad medium-voltage switchgear: circuit-breaker section interlocks","url":"https://productinfo.se.com/masterclad_mv_switchgear_ib/6055-30-masterclad-15kv-mv-switchgear-ib/English/6055-30%20Masterclad%20MV%20Switchgear%20Indoor%20%28bookmap%29_DD00646805.xml/%24/Section6-CircuitBreakerSectionInter-58DD6EC7","scope":"Breaker control, mechanism, position contacts, racking interlocks and test interfaces.","type":"manufacturer","checkedOn":"2026-11-03","reuse":"link-only","relevance":"Public technical context for switchgear interlocking functions. Breaker control, mechanism, position contacts, racking interlocks and test interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation."}]}