Side-by-side reference

Understand the difference.

Compare the meaning, drawing context and source references of two entries. A similar graphic or shared abbreviation does not establish equivalence.

First referenceCompare with

PB NO

Symbols

Normally open pushbutton

A normally open pushbutton combines an operator-actuated mechanism with a contact shown open in its defined normal state. Momentary and maintained or latching operation are separate characteristics that must be described explicitly.

Drawing use: Schematic
Application: Control circuits
Reference family: IEC / IEEE / ANSI

A distinction that matters

A NO contact symbol by itself does not identify the pushbutton actuator or its mechanical operating mode.

Full reference

PB NC

Symbols

Normally closed pushbutton

A normally closed pushbutton has a contact closed in its specified normal state. Actuation changes that contact state according to the selected operator and contact block. Momentary, maintained, latching and positive-opening characteristics must be identified from device documentation.

Drawing use: Schematic
Application: Control circuits
Reference family: IEC / IEEE / ANSI

A distinction that matters

An ordinary NC pushbutton and an emergency-stop device are not interchangeable solely because both drawings show a closed contact.

Full reference

Original educational previews. Follow the source references on each full entry for the appropriate standard or selected product.