What is work of avionic aircraft maintenance engineer?

Responsible for the work on the Avionics of an Aircraft composed of the following:

communications, navigation and guidance, display systems, flight management systems, sensors and indicators, weather radars, electrical systems and various other computers onboard modern aircraft and spacecraft. It also includes the hundreds of systems that are fitted to aircraft to meet individual roles; these can be as simple as a search light for a police helicopter or as complicated as the tactical system for an airborne early warning platform.