The GEA 71 is a micro-processor based input/output Line Replaceable Unit (LRU) used to monitor sensor inputs and drive annunciator outputs for aircraft airframe and engine systems. The GEA 71 interfaces with various sensors on the aircraft and communicates airframe and engine information via RS-485 digital interface to GIA 63(W) Integrated Avionics Units or IAUs. The GIAs then interface with the GDU Primary Flight Display(s) (PFD) and Multi-Function Display (MFD). Typically, the MFD shows engine instrumentation while the PFD normally shows airframe alerts provided by the GEA 71. Engine/airframe instrumentation is also displayed on the PFD and/or MFD while the system is in reversionary mode. The PFD and MFD displays serve as the user interface for the GEA 71.