This document defines the characteristics of first generation L-band satellite communication system installations including the avionics equipment. This document provides traditional form, fit, function, and interface standards for the installation of Satcom equipment for use in all types of aircraft. It defines the satellite data unit in a 6 MCU form factor. It also provides a summary description of each avionics component that would comply with this document. Supplement 14 adds references to ARINC Characteristic 781 and address equipment configurations and functionality associated with SwiftBroadband services.