介绍了中国铁路数据通信网现状，以及建设铁路综合数据网的必要性。

The current situation of Chinese railway data communication network was introduced, and the necessity to construct railway integrated data network was given.

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综合业务数字网(ISDN)是综合数字网的延伸，它打破了传统电话网和数据网之间的界限，扩展了网络业务的使用类型和范围。

As extension of IDN network, ISDN has broken the ambit between the traditional telephone network and data network, expanded the application types and scope of network operation.

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综合业务数字网(ISDN)是综合数字网的延伸，它打破了传统电话网和数据网之间的界限，扩展了网络业务的使用类型和范围。

As extension of IDN network, ISDN has broken the ambit between the traditional telephone network and data network, expanded the application types and scope of network operation.

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