# IEC non-retriggerable monostable

Canonical URL: https://eloragrid.ai/symbols/iec-non-retriggerable-monostable
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: 1⊓
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Rectangular element with the 1 and single-pulse qualifier
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.

IEC monostable marked with 1 and a single pulse: a trigger during the output pulse is ignored.

## In plain English

### What does IEC non-retriggerable monostable mean?

The non-retriggerable monostable produces one output pulse of fixed duration when triggered. Further triggers during that pulse have no effect. IEC drawings show the additional drawing mark 1 with a single pulse shape inside the outline, and timing component connections are shown as non-logic inputs.

### A simple example

These elements are used to stretch short events into pulses long enough to be seen by slower logic, or to produce a fixed-width command. The external resistor and capacitor that set the pulse width should be drawn next to the element and the nominal width stated.

### What the drawings help you do

Pulse width tolerance depends on the timing components and the device. The symbol shows the behaviour, not the accuracy.

### This particular reference

IEC monostable marked with 1 and a single pulse: a trigger during the output pulse is ignored. The retriggerable monostable extends its pulse on each new trigger and is drawn without the 1.

### Terms

- Normally open / normally closed: The contact state in the normal condition defined for the drawing.
- Terminal: An identified point where a conductor connects.
- Signal: Electrical information passed between devices, rather than necessarily the main power supply.

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)
- [SN74LS221 dual monostable multivibrators with Schmitt-trigger inputs](https://www.ti.com/lit/ds/symlink/sn74ls221.pdf)


## What it represents

The non-retriggerable monostable produces one output pulse of fixed duration when triggered. Further triggers during that pulse have no effect. IEC drawings show the qualifier 1 with a single pulse shape inside the outline, and timing component connections are shown as non-logic inputs.
These elements are used to stretch short events into pulses long enough to be seen by slower logic, or to produce a fixed-width command. The external resistor and capacitor that set the pulse width should be drawn next to the element and the nominal width stated.
Pulse width tolerance depends on the timing components and the device. The symbol shows the behaviour, not the accuracy.

## How to read it

- Retriggers during the pulse are ignored.
- Find the timing resistor and capacitor connections.

## Information to show or reference

- Show the single-pulse qualifier.
- Draw the timing components and state the nominal width.
- Mark trigger input edge sense.

## Important distinction

The retriggerable monostable extends its pulse on each new trigger and is drawn without the 1.

## Facts

- Retrigger behaviour: Ignored during pulse
- Example device: Dual monostable multivibrators with Schmitt-trigger inputs
- 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. Lists the nonretriggerable monostable general qualifier.
- [SN74LS221 dual monostable multivibrators with Schmitt-trigger inputs](https://www.ti.com/lit/ds/symlink/sn74ls221.pdf) — Texas Instruments. Manufacturer monostable multivibrator 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.