This standard specifies digital hierarchy format requirements. This standard is intended to be used in conjunction with the American National Standard for Telecommunications - Digital Hierarchy - Electrical Interfaces, T1.102-1993 (R1999). Compliance with this standard is necessary if the various networks that comprise the hierarchy are to be interconnected. Since this is an interconnect specification, no equipment design requirements are provided. Such requirements, and additional format specifications enabling end-to-end communication between terminals, will be found in the appropriate equipment specifications.