NOT
Logic inverter
Produces the opposite logical state of its defined digital input.
Schematic
IEC · 1
IEC NOT element (rectangular form)
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.
- 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.
Read the source: Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A) · SN74HC04 — digital inverters
IEC · 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.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
Schematic · 1
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.
A distinction that matters
A box marked 1 without output negation is a non-inverting buffer.
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)
Defines the 1 qualifier and logic negation.
SN74HC04 — digital inverters
Manufacturer inverter 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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