Push Button Symbol: NO, NC & Momentary Contacts

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• Read a push-button symbol, distinguish normally open from normally closed contacts, and separate momentary action from a maintained switch.
• Original symbol illustrations, a reading check and feedback for learning.

What does this symbol mean?

A push button is a manually operated control device that changes its contact state while it is actuated. In the common schematic convention a normally open (NO) contact is drawn open in the reference state and closes only while pressed; a normally closed (NC) contact is drawn closed and opens while pressed. A momentary button returns to its reference state when it is released.

The symbol describes contact action and the standard reference state. It does not state voltage, current rating, enclosure type, colour, illumination, ingress protection or safety function, and it is not the same as a maintained switch that keeps its position after actuation.

See the symbol

How to read it in context

1. Identify the drawing type, then find the device tag (often S or SB, or a project letter) and the push-button entry in the legend.
2. Read the contact in its documented reference state and decide whether it is NO or NC, then check for any note that names a momentary or maintained action.
3. Use the control schematic, device schedule and manufacturer data for contact form, colour, illumination, ratings and terminal numbers.
4. Treat the drawn state as documentation only; field state and safe work conditions come from the approved verification procedure.

Common look-alikes and mistakes

• A push button and a maintained switch can look similar; the action note and the legend separate momentary from maintained.
• NO and NC describe the defined reference state, not whether a field terminal is energized or safe to touch.
• An illuminated or metal push button can resemble an indicator lamp; read the tag, legend and circuit role instead of the appearance alone.
• The symbol does not make a control circuit safe to work on and does not authorize testing or repair.

Try the symbol-reading check

Standards, sources and related symbols

These are independently drawn teaching diagrams. They help you read a drawing, but the project legend, applicable standard and equipment documentation control the actual meaning. Editorial source check: 29 October 2026.

• IEC 60617 — graphical symbols for diagrams
• IEC 60617 — graphical symbols for diagrams
• US Department of Energy — Engineering Symbology, Prints, and Drawings
• Switch Symbol in Electrical Schematics & Floor Plans
• Contactor Symbol: Coil, Main Contacts & Control
• Relay Symbol on Electrical Drawings: Coil, NO/NC Contacts & Tags
• Electrical Drawing Symbols: 4 Core Diagram Types
• Content responsibility and review status