# IEC polarity indicator at input (active-low input)

Canonical URL: https://eloragrid.ai/symbols/iec-active-low-input-indicator
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: POL-IN
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: 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.

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.

### 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)


## 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.

## Important distinction

The negation circle is a logic statement that needs a declared convention; the triangle is a level statement.

## Facts

- Meaning: L level produces internal 1
- Equivalent in positive logic: Input negation circle
- 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. Explains the logic polarity indicator and why data books use it.

## 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.