最初定义为数字蜂窝电话网络的泛欧洲开放式标准，用来支持语音、数据、文本消息和过境漫游。
Originally defined as a pan-European open standard for a digital cellular telephone network to support voice, data, text messaging and cross-border roaming.
定义：ISDN(综合服务数字网络)，是一个国际转换标准，是为了语音和数据的数码拨号上网电话服务。
Definition of: ISDN (Integrated Services digital Network) an international standard for switched, digital dial-up telephone service for voice and data.
固定电话网、移动电话网、分组数据网与因特网的共存与融合需要制定许多标准才能实现。
Coexisting and converging of fixed networks, mobile networks, packet data networks and Internet needs a number of standards.
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