Airfield lighting simulation. Researchers testing an embedded computer system that operates lights in a model airfield. 'Embedded systems' combine computer software and hardware specifically to perform a dedicated function. One requirement of such systems is that they are fail-safe. Therefore, situations in which the technology will be used are simulated to test its effectiveness. The functioning of all lights on the airfield and the location of all planes is monitored by specially networked computers. A typical airfield has several thousand signal lamps. In this simulation they are replaced by light emitting diodes.