NEG-IN
IEC logic negation at input
Small circle where an input meets an outline: an external 0 produces the internal 1 (active) state.
IEC
IEC · POL-IN
IEC polarity indicator at input (active-low input)
Small triangle on an input lead meaning a low level produces the internal active state.
In plain English
What does IEC polarity indicator at input (active-low input) mean?
The polarity indicator is a small right-angled triangle drawn on the input line where it meets the outline. It states that the L level produces the internal 1 state. Because it refers directly to levels, it does not need a positive or negative logic declaration, which is why device data books favour it.
A simple example
On drawings that combine device-level schematics with functional logic, the polarity triangle tells the reader that a pin is active low, such as an enable, chip-select or reset input. In positive logic it means the same as a negation circle.
What the drawings help you do
The triangle does not indicate an internal pull-up or default state for an unconnected input. Those details are device data.
This particular reference
Small triangle on an input lead meaning a low level produces the internal active state. The negation circle is a logic statement that needs a declared convention; the triangle is a level statement.
- 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)
IEC · Right-angled triangle on the input line next to the outline
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.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
Schematic · POL-IN
What it represents
The polarity indicator is a small right-angled triangle drawn on the input line where it meets the outline. It states that the L level produces the internal 1 state. Because it refers directly to levels, it does not need a positive or negative logic declaration, which is why device data books favour it.
On drawings that combine device-level schematics with functional logic, the polarity triangle tells the reader that a pin is active low, such as an enable, chip-select or reset input. In positive logic it means the same as a negation circle.
The triangle does not indicate an internal pull-up or default state for an unconnected input. Those details are device data.
How to read it
- Read the triangle as active when low.
- Equivalent to a negation circle only in positive logic.
Information to show or reference
- Draw the triangle on the outside of the outline, pointing in the signal direction.
- Use it consistently in place of circles on level-based schematics.
- Name active-low nets with a consistent suffix or overbar.
A distinction that matters
The negation circle is a logic statement that needs a declared convention; the triangle is a level statement.
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)
Explains the logic polarity indicator and why data books use it.
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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