本标准定义了ISDN基本速率接口的最小承载服务集，它与CCITT体系结构概念密切一致，并明确考虑了美国电信环境中的服务约束。以前称为T1。604-1990（R2009）。

This standard defines the minimal set of bearer services for the ISDN basic rate interface, which conforms closely to CCITT architectural concepts and explicitly considers the service constraints in the telecommunications environment of the United States. Formerly known as T1.604-1990(R2009).