What Is an Andon Light?

If you have spent any time on a factory floor, you have likely seen the bright, colored lights mounted on machines or above workstations. These are Andon lights, and they are one of the most practical tools in modern manufacturing.

Whether you call them tower lights, stack lights, signal lights, or Andon lights, they all serve the same fundamental purpose: giving your team instant visual information about what is happening on the production floor.

The SL60 modular stack light is one of the most popular Andon lights for industrial applications.

Where Does the Word "Andon" Come From?

The word "Andon" comes from a Japanese term for a paper lantern. Toyota adopted the concept as part of the Toyota Production System in the mid-20th century, using lights and signals to let operators flag problems on the assembly line without delay. When a worker spotted a defect or needed help, they would activate the Andon signal. The line supervisor could see the alert immediately and respond before the issue moved downstream.

That core idea has not changed. An Andon light is still fundamentally about making problems visible the moment they happen, so the right people can respond fast.

What Does an Andon Light Actually Do?

An Andon light is a visual signaling device that communicates machine status, production conditions, or operator alerts using color-coded lights. Each color represents a specific condition. When a machine changes state, the corresponding light turns on, off, or flashes. They can also include a buzzer or audible alarm. This lets anyone on the floor see the status of a workstation from a distance, without walking over or checking a screen.

A typical setup uses green for running, yellow for caution, and red for stopped or fault. But you can configure the colors to mean whatever your operation needs. For a deeper look at color conventions, check out our guide on Andon color codes.

Most tower lights are controlled by a low-voltage signal (typically 24V DC or 110V AC) from a PLC, controller, or simple switch. Each light tier has its own wire, so you can control each color independently. 

Where Are Andon Lights Used?

Andon tower lights show up in virtually any environment where visual status communication matters:

• Manufacturing and assembly lines - machine status, cycle completion, fault alerts
• Warehousing and logistics - pick-to-light systems, conveyor status
• CNC and machining - spindle running, tool change needed, program complete
• Injection molding - cycle status, material feed, quality alerts
• Food and beverage processing - line status, sanitation alerts
• Offices and call centers - availability indicators, service queue status

What Types of Andon Lights Are Available?

There are several styles of Andon lights depending on your application. Modular stack lights let you choose individual color tiers. Multi-color signal lights display multiple colors from a single compact housing. Andon stations combine the light, control switch, and enclosure into one standalone unit. And wireless Andon lights communicate over RF when running cable is not practical.

Choosing between them depends on your mounting space, how many conditions you need to display, and whether the light will be controlled by a PLC or by an operator directly. For a detailed comparison, see our guide on choosing the right stack light.

Learn More

This article covers what an Andon light is and why it matters. If you want to go deeper, we have guides on related topics:

• Stack Light vs. Andon: What's the Difference?
• Andon Color Codes
• Choosing the Right Stack Light
• How to Wire an Andon Light