NO
Normally open contact
A contact shown open in the normal state defined for its device.
Schematic
Symbols · NC
Normally closed contact
A contact shown closed in the normal state defined for its device.
Schematic · NC
What it represents
A normally closed contact is closed in the normal state specified for its device. Actuating the parent device may open it. The drawing must establish that state convention and associate the contact with the appropriate equipment and terminal designations.
NC contacts occur in relay logic, indication and control circuits. The contact representation alone does not establish safety behaviour, failure response or suitability for a safety function. Those properties depend on the complete device and system design.
How to read it
- Follow the parent-device reference and the relevant circuit path.
- Check whether the drawing describes a de-energised, unactuated or explicitly stated operating state.
Information to show or reference
- Reference the parent device.
- Document the contact terminals.
- Explain any state convention that differs from the general legend.
A distinction that matters
An NC mark does not prove a circuit is fail-safe or establish positive-opening characteristics. Consult the selected device and complete control design.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Relays and contacts: public symbol reference
Public normally closed relay contact categories.
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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