NOR gate symbol

An OR gate with an inverting circle on its output.

Also known as: Inverted OR gate, Logical NOR gate

Engineering & technicalStandard profile

Meanings

A NOR gate outputs a one only when every input is a zero. Like the NAND gate it is functionally complete, and the two are the only gates from which all others can be built.

Officially standardisedVerified fact
Denotes an inverted OR gate: the output is true only when every input is false.
Contexts: Technical drawing, Electrical equipment
Officially standardisedVerified fact
Is, with the NAND gate, one of only two gates from which every other logic function can be constructed.
Contexts: Technical drawing, Electrical equipment

Visual description

A curved-back shape with a pointed front followed by a small hollow circle at the output.

Symmetry: horizontal
Orientation: upright

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

Logic gate
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol instructs and which standard governs it. Where a standard is named it is reported by this source rather than read, so no meaning is typed `official` on that basis.
ANSI Y32.2 / IEEE 315, Graphic Symbols for Electrical and Electronics Diagrams
IEEE / American National Standards Institute · retrieved 2026-08-22
Paywalled and NOT READ in full. Registered so the zig-zag resistor familiar from American schematics can be attributed to the standard that defines it, rather than described as the 'old' or 'wrong' form. See docs/paywalled-standards.md.
Electronic symbol
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.
IEC 60617, Graphical symbols for diagrams
International Electrotechnical Commission · retrieved 2026-08-22
Maintained as an online database and NOT READ in full. Registered so a circuit-diagram record can say which body defines its symbol, and so the divergence between the IEC form and the older American form can be recorded as a real standards difference rather than a drawing preference. See docs/paywalled-standards.md.
Circuit diagram
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.

Last reviewed 2026-08-23

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Meanings

A NOR gate outputs a one only when every input is a zero. Like the NAND gate it is functionally complete, and the two are the only gates from which all others can be built.

Officially standardisedVerified fact

Denotes an inverted OR gate: the output is true only when every input is false.

Contexts: Technical drawing, Electrical equipment

Officially standardisedVerified fact

Is, with the NAND gate, one of only two gates from which every other logic function can be constructed.

Contexts: Technical drawing, Electrical equipment

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

Logic gate
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol instructs and which standard governs it. Where a standard is named it is reported by this source rather than read, so no meaning is typed `official` on that basis.
ANSI Y32.2 / IEEE 315, Graphic Symbols for Electrical and Electronics Diagrams
IEEE / American National Standards Institute · retrieved 2026-08-22
Paywalled and NOT READ in full. Registered so the zig-zag resistor familiar from American schematics can be attributed to the standard that defines it, rather than described as the 'old' or 'wrong' form. See docs/paywalled-standards.md.
Electronic symbol
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.
IEC 60617, Graphical symbols for diagrams
International Electrotechnical Commission · retrieved 2026-08-22
Maintained as an online database and NOT READ in full. Registered so a circuit-diagram record can say which body defines its symbol, and so the divergence between the IEC form and the older American form can be recorded as a real standards difference rather than a drawing preference. See docs/paywalled-standards.md.
Circuit diagram
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for what the component is, how its symbol is conventionally drawn, and where the ANSI and IEC conventions differ. Not used for any claim about the text of IEC 60617, which is paywalled and was not consulted.

Last reviewed 2026-08-23