NO
Normally open contact
A contact shown open in the normal state defined for its device.
Schematic
Symbols · MBB
Make-before-break changeover contact
A make-before-break changeover contact establishes the next path before releasing the previous path during its documented transfer.
Schematic · MBB
What it represents
A make-before-break changeover contact establishes the next path before releasing the previous path during its documented transfer. The temporary overlap must be understood for the connected circuits.
How to read it
- Identify any circuits that would be interconnected during the overlap.
- The preview is an original explanation of this function. Match the actual drawing convention to its legend and the selected equipment documentation.
Information to show or reference
- Label common and throw terminals
- State overlap sequence
- Reference connected-circuit compatibility
A distinction that matters
A break-before-make transfer opens the previous path before establishing the next.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
AutoCAD Electrical: Level, flow, keyed and measurement switches
Public documentation of this equipment function or named vendor variant; the illustration is independently authored and is not the source graphic.
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.
Explore related references
Put the reference into a drawing workflow.
Elora Grid helps electrical teams work with drawings, specifications and equipment information. Explore the drafting workflow or join the early-access waitlist.