This ARINC Standard defines the installation characteristics of second generation L-band satellite communication systems. It provides the traditional form, fit, function, and interfaces for the installation of satcom equipment for use in all types of aircraft. Description of avionics equipment (e.g., Satellite Data Unit (SDU), Antennas, etc.) are included. Supplement 6 adds references to new Diplexer/Low Noise Amplifiers (DLNAs) defined in Supplement 8 to ARINC Characteristic 781: Mark 3 Aviation Satellite Communication Systems. The five new DLNAs are intended to protect Inmarsat Classic Aero and SwiftBroadband (SBB) satcom equipment from ground-based cellular sources, such as cellular Long Term Evolution (LTE) and Ancillary Terrestrial Component (ATCt). The DLNAs are categorized by desired features and service (e.g., new DLNA versus drop-in replacement, LTE and/or ATCt protection, Classic Aero and/or SBB service).