The INTELSAT TDMA/DSI System is a complex, centrally‐controlled communications system, the performance of which will depend to some extent on the effectiveness of the alignment, maintenance and testing procedures. However, the wide range of disciplines encountered in the system mean staff currently familiar with the existing FDMA network may have difficulty with these new and unfamiliar fields. The purpose of this series of four papers is to provide an understanding of the necessity for, and operation of, the SSOG test procedures for the INTELSAT TDMA/DSI system. In this first part, the overall system and its testing requirements will be discussed as a foundation for a discussion of the SSOG tests in Part 2.