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IEC retriggerable monostable
IEC monostable showing only the single-pulse qualifier; each new trigger restarts the output pulse.
IEC
IEC · 1⊓
IEC non-retriggerable monostable
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.
- 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.
Read the source: Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A) · SN74LS221 dual monostable multivibrators with Schmitt-trigger inputs
IEC · 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.
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 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.
A distinction that matters
The retriggerable monostable extends its pulse on each new trigger and is drawn without the 1.
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)
Lists the nonretriggerable monostable general qualifier.
SN74LS221 dual monostable multivibrators with Schmitt-trigger inputs
Manufacturer monostable multivibrator 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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