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When selecting push button switches for industrial control, cabinet wiring and electronic DIY projects, you will often encounter the markings 1NO, 1NC and 1NO1NC on product datasheets. These labels describe the internal contact configuration of the button switch and directly affect circuit wiring logic. This article explains the definition and practical differences of these common switch contact types.
Push button switches are widely used in automation equipment, control panels, machinery, and custom electronic projects. Before purchasing, buyers need to understand contact definitions marked NO and NC, which are the core parameters to match your circuit design.
NO stands for Normally Open. A 1NO push button switch means it has one normally open contact. In its natural, unpressed state, the contact remains disconnected and no current can pass through. When the button is pressed, the contact closes and the circuit turns on. Once released, the circuit opens again. This type is commonly used for start signal triggering.
NC stands for Normally Closed. A 1NC push button switch comes with one normally closed contact. Without pressing the button, the contact keeps closed and the circuit stays conductive. Pressing the button breaks the connection and cuts off the current. It is frequently applied in stop circuits and safety interlock systems.
1NO1NC means the push button integrates one normally open contact plus one normally closed contact inside a single switch unit. This structure is also known as SPDT, single pole double throw. One button can simultaneously output two opposite signals: pressing the button closes the NO contact and opens the NC contact at the same time.
This 1NO1NC combination brings great convenience. Engineers and DIY users only need to install one button to get both start and stop feedback signals, saving installation space and reducing wiring work. It is the most popular choice for industrial control panels.
Quick Comparison
1NO：1 Normally Open, circuit OFF at rest, ON when pressed 1NC：1 Normally Closed, circuit ON at rest, OFF when pressed 1NO1NC：1NO +1NC integrated, dual opposite signals in one button
Application Tips
- Use 1NO for start buttons, signal trigger
- Use 1NC for emergency stop, safety protection
- Choose 1NO1NC if you need both signals from one push button
When ordering a pushbutton switch, confirm the contact type (1NO/1 NC/1NO1 NC) to avoid circuit mismatches. We offer a full range of momentary and self-locking push-button switches with different contact options for your choice.
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