EVERBRIGHT TECH TIP – NO vs NC

🔧 NO vs NC — What’s the Difference?

If you’ve worked with push buttons, relays or control circuits, you’ve probably come across NO and NC.

But what do they actually mean?

NO = Normally Open
The contact is open when the device is in its normal, unactivated state. When activated, the contact closes.

NC = Normally Closed
The contact is closed in its normal state. When activated, the contact opens.

A simple example:
🔘 START button → commonly uses NO contact
🛑 STOP button → commonly uses NC contact

Why is a STOP button commonly NC?

Because if there is a broken wire or loss of connection in the control circuit, the circuit can be designed to stop rather than continue operating.

Understanding NO and NC is one of the basics of industrial control circuits—but it’s an important one!

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