# ANSI three-input NOR gate

Canonical URL: https://eloragrid.ai/symbols/ansi-three-input-nor-gate
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: NOR3
Drawing use: Schematic
Reference families: IEEE / ANSI, Manufacturer

## Symbol convention

Convention: IEEE / ANSI
Form: OR outline with three inputs and an output bubble
Distinctive-shape form as used in IEEE/ANSI-style schematics and manufacturer data books. Independent educational drawing; exact standard geometry and compliance are not asserted. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.
Related representation: [NOR gate](https://eloragrid.ai/symbols/logic-nor-gate)

Three-input OR outline with an output bubble; the output is high only when all three inputs are low.

## In plain English

### What does ANSI three-input NOR gate mean?

The three-input NOR gate is the OR outline with three inputs and a bubble at the pointed output. The output is high only when all inputs are low. Triple three-input NOR packages provide the function and it is often used to create an all-clear signal.

### A simple example

When all inputs are themselves active-low alarm lines, the same function may be easier to read as an AND outline with bubbled inputs. A consistent choice across the drawing set makes reviews quicker.

### What the drawings help you do

The symbol does not show output drive strength or whether the output may be wired to others. Check the device type before connecting outputs together.

### This particular reference

Three-input OR outline with an output bubble; the output is high only when all three inputs are low. An AND outline with three bubbled inputs is the De Morgan equivalent of this gate.

### Terms

- Terminal: An identified point where a conductor connects.
- 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.

- [SNx4HC27 triple 3-input NOR gates](https://www.ti.com/lit/ds/symlink/sn74hc27.pdf)


## What it represents

The three-input NOR gate is the OR outline with three inputs and a bubble at the pointed output. The output is high only when all inputs are low. Triple three-input NOR packages provide the function and it is often used to create an all-clear signal.
When all inputs are themselves active-low alarm lines, the same function may be easier to read as an AND outline with bubbled inputs. A consistent choice across the drawing set makes reviews quicker.
The symbol does not show output drive strength or whether the output may be wired to others. Check the device type before connecting outputs together.

## How to read it

- Look for the output bubble at the point of the outline.
- Check whether a De Morgan form is used elsewhere for the same signal.

## Information to show or reference

- Show the output bubble clearly.
- Name the condition each input represents.
- Note the device section and pin numbers.

## Important distinction

An AND outline with three bubbled inputs is the De Morgan equivalent of this gate.

## Facts

- Inputs: Three
- Output high when: All inputs low
- Artwork scope: Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic

## Public references

- [SNx4HC27 triple 3-input NOR gates](https://www.ti.com/lit/ds/symlink/sn74hc27.pdf) — Texas Instruments. Manufacturer documentation for triple three-input NOR gates.

## 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.