This ETS specifies the characteristics of an access digital section for the Integrated Services Digital Network (ISDN) primary rate access between the user-network interface (at the T reference point@ defined in ETS 300 011 [1]) and the local exchange (at the V.3 reference point@ defined in CCITT Recommendation Q.512 [4]) supporting the primary rate interface channel structure defined in CCITT Recommendation I.412 [3] and ETS 300 011 [1] and the additional functions required for operation and maintenance of the access digital section according to ETR 001 [2]@ Option 2. The requirements of this ETS satisfy network performance requirements of CCITT Recommendations G.821 [5] on error performance as well as CCITT Recommendations G.801 and I.350 with regard to availability. Annex A (normative) to this ETS specifies requirements for interworking between the Primary Rate Access Digital Section (DS) and the Exchange Termination (ET) and the definition of the ET layer 1 state machine which are outside the scope of this ETS but which are nevertheless important. Annex B (normative) specifies a modification of the requirements when Line Termination (LT) and ET functions are combined in one unit. Annex C (normative)@ to be provided@ will specify the requirements for conformance testing. This ETS does not specify the requirements of the digital transmission system used within the access digital section.