This document covers maintenance of the Basic Rate Access (BRA) 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 basic 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 basic 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. Clause 2 lists referenced documents. Clause 3 provides definitions of new terms introduced by this standard. Clause 4 describes BRA models that are used in Clauses 5 and 6 to help describe the required capabilities for maintenance of the Customer Access@ and the optional capabilities for maintenance of the Customer Installation. Annex A gives guidance on the use of performance monitoring capabilities from the user point of view. A list of acronyms used in this document is provided in annex B.