Definition
A digital logic circuit whose output is high (logic 1) only when all of its inputs are low (logic 0). If any input is high, the output is low. It is the logical inverse of an OR gate.
Plain English
An electronic switch that turns its output ON only when every input is OFF. As soon as any input turns ON, the output turns OFF.
Context Anchor
Seen mainly in aircraft electronics, avionics maintenance, and digital circuit descriptions, rather than in normal cockpit procedures.
Derivation
The name combines NOT and OR. An OR gate gives a high output if any input is high. Putting NOT in front inverts that result, so the gate is called NOR — "not OR."
Why Pilots Care
Pilots don't operate gates directly, but understanding them helps when troubleshooting avionics or interpreting how warning and annunciator systems decide when to trigger or stay silent.
Analogy
Think of a panel light that comes on only when two switches are both off. If either switch is turned on, the light goes out. That is the basic idea of a NOR gate.
Intuition Check
Do not picture a physical gate or read “nor” only as a grammar word. In electronics, a NOR gate is a circuit whose output is the opposite of an OR decision: any yes input makes the output no.
Example Sentence 1
The annunciator panel uses a NOR gate so the "all systems normal" light stays on only when none of the fault inputs are active.
Example Sentence 2
A failed NOR gate prevented the proper interlock between the two sensor inputs.