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由东京NTT 所经营的日本全国通信网现正按照最新国际标准——同步数字系列(SDH)技术“网路节点接口”(NNI)的要求进行技术改造。包括数字微波和光纤传输系统两种方式的NNI 通信线路已于1990年3月在日本许多地方投入商用。为了把它的通信网改造成能够提供各种宽带ISDN 业务的高速数字网,NTT 从1989年末就在国内开始使用这种新技术。NNI 是1988年由CCITT 提出的一项新的数字技术建议,以实现全世界数字网的标准化。
Japan’s national communications network, operated by Tokyo’s NTT, is now undergoing technological transformation as required by the latest international standard, Synchronous Digital Hierarchy (SDH) Network Node Interface (NNI). The NNI communication line, which includes both digital microwave and fiber optic transmission systems, was commercially available in many parts of Japan in March 1990. In order to transform its communications network into a high-speed digital network capable of providing a wide range of broadband ISDN services, NTT started to use the new technology domestically from the end of 1989. NNI is a new digital technology proposal put forward by the CCITT in 1988 to standardize digital networks around the world.