# IEC binary decoder (X/Y coder)

Canonical URL: https://eloragrid.ai/symbols/iec-binary-decoder
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: BIN/OCT
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Rectangular coder with X/Y qualifier such as BIN/OCT
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: [Binary decoder / demultiplexer](https://eloragrid.ai/symbols/binary-decoder-demultiplexer)

IEC coder marked BIN/OCT or similar, converting a binary input code into one active output.

## In plain English

### What does IEC binary decoder (X/Y coder) mean?

IEC coders use the general additional drawing mark X/Y, where X is the input code and Y is the output code. A three-to-eight-line decoder is therefore marked BIN/OCT, with input weights 1, 2 and 4 and outputs numbered 0 to 7. Enable inputs are often combined with an & element in the common-control area.

### A simple example

Decoders select one of several devices, relays or indicator lines from a binary code. A drawing should keep the output numbers so a reviewer can confirm that, for example, input code 5 activates output 5.

### What the drawings help you do

The additional drawing mark says nothing about output polarity; polarity triangles at outputs show active-low outputs, which are common on decoder devices.

### This particular reference

IEC coder marked BIN/OCT or similar, converting a binary input code into one active output. A BCD/7SEG coder produces segment drive patterns, not one-of-n outputs.

### Terms

- Coil: A wound conductor that can produce a magnetic field when energised.
- 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)
- [SN74HC138 — binary decoding and demultiplexing](https://www.ti.com/lit/ds/symlink/sn74hc138.pdf)


## What it represents

IEC coders use the general qualifier X/Y, where X is the input code and Y is the output code. A three-to-eight-line decoder is therefore marked BIN/OCT, with input weights 1, 2 and 4 and outputs numbered 0 to 7. Enable inputs are often combined with an & element in the common-control area.
Decoders select one of several devices, relays or indicator lines from a binary code. A drawing should keep the output numbers so a reviewer can confirm that, for example, input code 5 activates output 5.
The qualifier says nothing about output polarity; polarity triangles at outputs show active-low outputs, which are common on decoder devices.

## How to read it

- X/Y gives input and output codes.
- Check output polarity marks before reading the truth table.

## Information to show or reference

- State the code pair, such as BIN/OCT.
- Show input weights.
- Mark active-low outputs.

## Important distinction

A BCD/7SEG coder produces segment drive patterns, not one-of-n outputs.

## Facts

- Qualifier: X/Y, for example BIN/OCT
- Outputs: One-of-n selection
- 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. X/Y coder qualifier and coder examples.
- [SN74HC138 — binary decoding and demultiplexing](https://www.ti.com/lit/ds/symlink/sn74hc138.pdf) — Texas Instruments. Binary decoder and demultiplexer 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.