In lean manufacturing, the alert system that lets workers signal or stop production for a quality problem is called andon.
An andon system notifies supervisors, maintenance staff, and other workers when a defect, equipment failure, material shortage, or safety concern occurs. A worker may activate it with a pull cord or button, while some systems trigger automatically through production equipment. Lights, sounds, text displays, or other signals can show where the problem occurred.
The system is closely associated with Toyota’s production system and the quality-control principle of jidoka, often translated as automation with a human touch. At Toyota, an initial alert may request assistance without immediately stopping the line; if the problem cannot be corrected quickly, production can be halted so defective work does not continue downstream.
Andon is sometimes confused with poka-yoke, which means mistake-proofing, or kanban, a scheduling and replenishment method. Gemba refers to the actual workplace, not the alert mechanism itself.