DEC
Binary decoder / demultiplexer
Uses binary selection and enable conditions to activate the documented selected output.
Schematic
IEC · BIN/OCT
IEC binary decoder (X/Y coder)
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.
- 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.
Read the source: Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A) · SN74HC138 — binary decoding and demultiplexing
IEC · 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.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
Schematic · BIN/OCT
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.
A distinction that matters
A BCD/7SEG coder produces segment drive patterns, not one-of-n outputs.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)
X/Y coder qualifier and coder examples.
SN74HC138 — binary decoding and demultiplexing
Binary decoder and demultiplexer documentation.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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