"In this standard@ the minimal set of bearer services for the basic rate interface for the integrated services digital network (ISDN) that conforms closely to the architectural concepts described by CCITT are defined. The telecommunications environment in the United States for the ISDN basic rate interface is explicitly considered. The bearer services defined in this standard are the minimal set of services defined in Bearer Services Supported by and ISDN@ CCITT Recommendation 1.211@1 which are to be supported by public networks for the ISDN basic rate interface. The description method used by CCITT@ which is called the ""method for the characterization of telecommunication services supported by an ISDN and network capabilities of an ISDN@"" is summarized in Section 4@ and the description of the essential bearer services that should be supported by a public ISDN in the United States follows in Section 5. The signaling procedures for these bearer services are defined in American National Standard for Telecommunications- Integrated Services Digital Network (ISDN) Data-Link Layer Signalling Specification for Application at the User-Network Interface@ ANSI T1.602-1989@ American National Standard for Telecommunications- Integrated Services Digital Network (ISDN)- Layer-3 Signaling Specification for Circuit Switched Bearer Service for Digital Subscriber Signaling System Number 1 (DSSSI)@ ANSI T1.607@2 and American National Standard for Telecommunications- Integrated Services Digital Network (ISDN)-Layer-3 Signaling Specification for X.25 Packet Switched Bearer Service for Digital Subscriber Signaling System Number 1 (DSSSI)@ ANSI T1.608.2 Digital communication between the user and the network equipments is defined in American National Standard for Telecommunications - Integrated Services Digital Network (ISDN) - Basic Access Interface for Use on Metallic Loops for Application on the Network Side of the NT (Layer 1 Specification)@ ANSI Tl.601-1988@ and American National Standard for Telecommunications - Integrated Services Digital Network (ISDN) - Basic Access Interface for S and T Reference Points (Layer 1 Specification)@ ANSI Tl.605-1989. 1 The designation numbers for the CCITT Recommendations that appear in this standard refer to the 1984 CCITT Red Book. Contact the secretariat for more recent information. 2 This standard is currently under development. Contact the secretariat for more recent information."