# IEC odd-parity element

Canonical URL: https://eloragrid.ai/symbols/iec-odd-parity-element
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: 2k+1
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Rectangular element with the 2k+1 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. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.
Related representation: [Parity generator / checker](https://eloragrid.ai/symbols/parity-generator-checker)

Element marked 2k+1 that is active when an odd number of inputs are active, as used for parity.

## In plain English

### What does IEC odd-parity element mean?

The 2k+1 additional drawing mark means the output is active when an odd number of inputs are active. It is what a cascade of two-input exclusive-OR gates actually computes, and it is the correct IEC additional drawing mark for an odd-parity tree drawn as a single element.

### A simple example

Drafters converting older drawings sometimes mark a multi-input parity tree as =1. That is wrong under the IEC meaning, because =1 requires exactly one active input. Replacing it with 2k+1 removes the ambiguity.

### What the drawings help you do

The element does not indicate the number of data bits on its own; show the full input set or a grouped bus with its width.

### This particular reference

Element marked 2k+1 that is active when an odd number of inputs are active, as used for parity. The =1 element gives the same result 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)
- [SN74LS280 — odd/even parity generation and checking](https://www.ti.com/product/SN74LS280)


## What it represents

The 2k+1 qualifier means the output is active when an odd number of inputs are active. It is what a cascade of two-input exclusive-OR gates actually computes, and it is the correct IEC qualifier for an odd-parity tree drawn as a single element.
Drafters converting older drawings sometimes mark a multi-input parity tree as =1. That is wrong under the IEC meaning, because =1 requires exactly one active input. Replacing it with 2k+1 removes the ambiguity.
The element does not indicate the number of data bits on its own; show the full input set or a grouped bus with its width.

## How to read it

- Do not read 2k+1 as exactly one active.
- Check whether the result is used as odd or even parity downstream.

## Information to show or reference

- Use 2k+1 for multi-input parity trees.
- State the word width.
- Reference the parity convention used by the protocol or memory.

## Important distinction

The =1 element gives the same result only for two inputs.

## Facts

- Qualifier: 2k+1 (odd number active)
- Two-input equivalent: Exclusive-OR
- 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 2k+1 and contrasts it with =1.
- [SN74LS280 — odd/even parity generation and checking](https://www.ti.com/product/SN74LS280) — Texas Instruments. Manufacturer parity generator and checker 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.