# IEC NOT element (rectangular form)

Canonical URL: https://eloragrid.ai/symbols/iec-not-gate
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: 1
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Single-input element marked 1 with output negation
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. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.
Related representation: [Logic inverter](https://eloragrid.ai/symbols/logic-inverter)

Single-input IEC box marked 1 with a negation at the output, inverting the logic state.

## In plain English

### What does IEC NOT element (rectangular form) mean?

The IEC inverter is a single-input element carrying the additional drawing mark 1, meaning the one input must be active, together with a negation at the output. The result is that the output is active when the input is inactive. Data books often replace the circle with a polarity triangle to show an active-low output.

### A simple example

Because negation can be drawn directly on any input or output, a standalone NOT box is often only used where an inverter really exists as a component or as a separate program instruction. On purely functional logic sheets drafters usually fold the inversion into the next element as a negated input.

### What the drawings help you do

The symbol gives no information about input thresholds. A Schmitt-trigger inverter adds the hysteresis additional drawing mark; without it, slow or noisy inputs may not be handled cleanly.

### This particular reference

Single-input IEC box marked 1 with a negation at the output, inverting the logic state. A box marked 1 without output negation is a non-inverting buffer.

### Terms

- Normally open / normally closed: The contact state in the normal condition defined for the drawing.
- 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)
- [SN74HC04 — digital inverters](https://www.ti.com/lit/ds/symlink/sn74hc04.pdf)


## What it represents

The IEC inverter is a single-input element carrying the qualifier 1, meaning the one input must be active, together with a negation at the output. The result is that the output is active when the input is inactive. Data books often replace the circle with a polarity triangle to show an active-low output.
Because negation can be drawn directly on any input or output, a standalone NOT box is often only used where an inverter really exists as a component or as a separate program instruction. On purely functional logic sheets drafters usually fold the inversion into the next element as a negated input.
The symbol gives no information about input thresholds. A Schmitt-trigger inverter adds the hysteresis qualifier; without it, slow or noisy inputs may not be handled cleanly.

## How to read it

- Check whether the inversion is a real component or only a notation choice.
- Look for a hysteresis mark if the input comes from a slow signal.

## Information to show or reference

- Mark the box with 1 and negate the output.
- Avoid stacking inverters when a negated input would do.
- Reference the device when the inverter is a discrete part.

## Important distinction

A box marked 1 without output negation is a non-inverting buffer.

## Facts

- Qualifier: 1 with output negation
- Input count: One
- 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 1 qualifier and logic negation.
- [SN74HC04 — digital inverters](https://www.ti.com/lit/ds/symlink/sn74hc04.pdf) — Texas Instruments. Manufacturer inverter documentation.

## 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.