Recommendation G.704 is a technical standard issued by the International Telecommunication Union’s Telecommunication Standardization Sector (ITU-T). It forms a part of the G-Series recommendations, which govern transmission systems and media.

• Official Designation: ITU-T Recommendation G.704 (10/98)
• Title: Synchronous frame structures used at 1544, 6312, 2048, 8448 and 44 736 kbit/s hierarchical levels
• Core Purpose: To provide the functional characteristics of digital interfaces, ensuring standardized data framing across different network equipment.
• Applicability: The standard applies to interfaces associated with:
  • Synchronous digital multiplex equipment.
  • Digital exchanges used for telephony and ISDNs.
  • PCM multiplexing equipment.
• Scope Limitations:
  • The recommendation does not cover electrical characteristics, which are defined in Recommendation G.703.
  • It does not necessarily apply to interfaces dedicated to non-switched connections, such as those used for transporting encoded wideband signals like broadcast TV.