This standard specifies the requirements for interchangeability, installation, hardware and software design, and equipment testing of civil aircraft avionics equipment (hereinafter referred to as avionics equipment). This standard applies to digital avionics equipment, including systems, subsystems, equipment and LRU (Line Replaceable U-nit, field replaceable unit). When applying this standard, its content may be tailored to meet the specific requirements for avionics equipment of a specific aircraft.