The word Andon (行灯) is Japanese for a paper lantern. In a factory it refers to a visual signal system, usually a stacked light tower, a display board or an app notification, that communicates the real-time status of a workstation, cell or line. Green means running normally. Yellow means the operator needs help. Red means the line has stopped.
Any operator can trigger an Andon by pulling a cord, pressing a button, or (increasingly) tapping a tablet. The signal alerts a team leader, who has a defined response time to arrive at the station. If the problem cannot be solved within one takt cycle, the line stops. This is the opposite of hiding problems, it is designed to surface them fast so they can be resolved permanently.
Andon builds two habits that healthy production depends on: operators speak up, and leaders show up. It shortens the distance between a defect appearing and the root cause being addressed. Without Andon, small problems accumulate silently and become big ones, scrap, rework, missed shipments, injuries.
Modern digital Andon extends the same principle beyond the physical light tower. Signals reach the right people through phones, screens and dashboards, and every call is timestamped and logged. That data becomes the raw material for improvement: which stations call for help most often, what response times look like, and where standardized work is breaking down.
