This document covers maintenance of the Primary Rate Access (PRA) physical layer@ which consists of equipment and facilities that exist as part of the customer access and the customer installation (see figure 1). Maintenance of the data-link and network layers associated with the primary rate interface is covered in another ISDN management standard. Purpose The purpose of this standard is to establish required capabilities for the maintenance and operations needed for the primary rate physical layer associated with access to Integrated Services Digital Networks (ISDNs).This standard establishes needed maintenance functionality in customer and network equipment@ particularly from the perspective of maintenance functionality available at the network boundary and from Operations Systems. Structure Clause 1 describes the purpose@ scope@ and structure of this document. Section 2 lists referenced documents. Clause 3 provides definitions of new terms introduced by this standard. Clause 4 describes PRA models that are used in Clause 5 to help describe the required maintenance capabilities. PRA maintenance topics for further study are discussed in annex A. Details of the relationships at the customer installation between the maintenance capabilities at the various interfaces and reference points in the ISDN reference model and the physical interfaces to the primary rate customer equipment are provided in annex B. PRA equipment interface operations under fault conditions are described in annex C. A list of acronyms used in this document is provided in annex E. A bibliography of related standards appears in annex F.