The standard instrument cluster contains a microprocessor. The instrument panel cluster (IPC) microprocessor communicates with other controllers in the vehicle over the Class 2 serial data line. The information passed over the Class 2 serial data line, along with direct external connections to other controllers and devices provides the inputs that are used to operate all of the gauges and the illuminated displays in the cluster. Some displays and gauges are operated directly by external sources (devices or controllers) and others are under software control of the IPC. As the IPC microprocessor runs the operating software, the microprocessor continuously processes Class 2 data in order to determine the correct values and states to display.