The requirements in this Standard apply to a device between an end-user DTE and the network interface (NI) of an intraLATA or interLATA carrier generally referred to as NCTE and herein referred to as SCDSU. This Standard includes the framing formats, pulse density requirements, physical, electrical protection, signaling, maintenance, end-to-end compatibility requirements and other necessary criteria for the proper operation of a customer's DTE with PSDS. This Standard does not include the requirements for ISDN, but does include the functions required for interworking with ISDN.

Specific implementations of PSDS can, and some currently do, offer subrate service over PSDS using rate adaption. This Standard, however, does not address rate adaption for subrate services. Those interested in specific implementations of subrate services using rate adaption over PSDS should contact the appropriate manufacturer or service provider.

The digital interface areas in Part 68 are currently under consideration. This Standard gives adequate design latitude to comply with current service offerings not requiring Part 68 compliance. Should compliance be required in the future, changes to this Standard might be required.