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

KEY NC

Symbols

Key-operated normally-closed switch

A key-operated NC switch opens its reference closed contact through the key mechanism. Its access and switching functions must be documented separately.

Drawing use: Schematic
Application: Control circuits
Reference family: IEC / Manufacturer

A distinction that matters

NC identifies the contact reference state, not a guarantee of tamper-proof control.

Full reference

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

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