# IEC logic identity element Canonical URL: https://eloragrid.ai/symbols/iec-logic-identity-element Publisher: Elora Grid Updated: 2026-10-28 Lookup label: = Drawing use: Schematic Reference families: IEC, Manufacturer ## Symbol convention Convention: IEC Form: Rectangular element with the = general qualifier 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. Element marked = whose output is active only when all inputs stand at the same logic state. ## In plain English ### What does IEC logic identity element mean? The = additional drawing mark defines a logic identity function: the output is active when every input is in the same state, whether all active or all inactive. For two inputs this is the equivalence or exclusive-NOR function, but with three or more inputs it is a distinct agreement check. ### A simple example Identity elements are useful for voting and agreement logic, such as confirming that three redundant transmitters agree before allowing an action. The drawing should state what happens on disagreement, since the element only reports whether agreement exists. ### What the drawings help you do The symbol does not provide majority selection. If two-out-of-three voting is intended, a different element or a combination of AND and OR elements is needed. ### This particular reference Element marked = whose output is active only when all inputs stand at the same logic state. A negated =1 element means not exactly one active; it matches identity only for two inputs. ### Terms - Signal: Electrical information passed between devices, rather than necessarily the main power supply. - Schematic: A drawing showing function and connections rather than physical appearance. Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram. - [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf) ## What it represents The = qualifier defines a logic identity function: the output is active when every input is in the same state, whether all active or all inactive. For two inputs this is the equivalence or exclusive-NOR function, but with three or more inputs it is a distinct agreement check. Identity elements are useful for voting and agreement logic, such as confirming that three redundant transmitters agree before allowing an action. The drawing should state what happens on disagreement, since the element only reports whether agreement exists. The symbol does not provide majority selection. If two-out-of-three voting is intended, a different element or a combination of AND and OR elements is needed. ## How to read it - With three or more inputs, read = as all equal, not as majority. - Check what downstream logic does on a disagreement. ## Information to show or reference - Use = only where full agreement is intended. - Label redundant inputs with their channel identifiers. - Show the disagreement response on the same sheet. ## Important distinction A negated =1 element means not exactly one active; it matches identity only for two inputs. ## Facts - Qualifier: = (all inputs same state) - Two-input equivalent: Exclusive-NOR - Artwork scope: Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic ## Public references - [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf) — Texas Instruments. Defines the = logic identity qualifier. ## Graphic scope Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.