Andon is a Japanese term related to manufacturing that refers to a system that notifies management, maintenance, and other employees of a quality, quantity, or process problem within a process. The signboard that shows this problem is located centrally, and signals using lights that indicate the specific workstation that has the problem and requires attention in order to complete or continue a process. Some machines can completely stop their process in order to receive the proper attention without continuing a wasteful procedure. The alert given can be automatically activated by the production equipment or machines themselves, but may also be activated manually by an employee by pulling a cord or pressing a button.

Some modern systems have new methods that expose the issues via alerts such as audio alarms, text, graphics, or other means of displaying the problem properly. Audio alerts may be given via coded tones, music with distinctive tunes relating to the alert, or pre-recorded verbal messages. There are some common reasons found for manual activation of the Andon which include shortage in parts, a defect has been made or found, malfunction of tools, or a problem revolving around safety.

The work is stopped until a solution has been found and the issue has been controlled. The alerts may be logged to a database so they can be concentrated on as a major aspect of a continuous-improvement program. The record contains information regarding the situation where the alert was generated, and potentially can provide a description of the event. This allows record to be kept of issues which can be quickly resolved and/or avoiding in the future.

This system, called the Andon System, is one of the key elements within the Jidoka quality-control method which can be traced back to the Toyota business as part of the Toyota Production System, and is therefore considered part of the Lean approach which promotes a lean environment within a manufacturing business as a way to essentially avoid waste and increase overall quality and production. It gives the laborer the capacity, and in addition the strengthening, to stop production when an imperfection is found, and the ability to quickly call for help and repair the issue to continue production without waste.