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一、ISDN发展简史 由于公共电话网络对非话音业务传输的固有限制,早已不能满足人们对数据、图形图象,乃至视频等非话音信息的通信需求。为此电信部门不得不建设各种通信网络,包括用户电报网、电路交换数据网、分组交换网及其它专用网。 虽然上述专网在一定程度上解决了当时急需的问题,但是存在通信网络标准不统一、经济性差、效率低、使用不便、用户与管理部门的关系复杂等缺点。 针对以上问题,70年代初,欧洲国家电信部门开始寻找新技术解决问题。ISDN的出现立即引起业界的广泛关注。但由于通信协调障碍和政策影响,直至90年代ISDN才开始在全世界范围内普及应用。1993年底,由22个欧洲国家的电信
First, a brief history of the development of ISDN Because of the inherent limitations of the public telephone network transmission of non-voice services, has long been unable to meet people’s data, graphics, graphics and video and other non-voice communication needs. To this end the telecommunications sector had to build a variety of communication networks, including subscriber telegraph networks, circuit-switched data networks, packet-switched networks and other private networks. Although the private network to some extent to solve the much-needed problems at the time, but there are not unified communications network standards, poor economy, low efficiency, inconvenience in use, the relationship between users and the management of complex shortcomings. In response to the above questions, in the early 1970s, European national telecommunication departments began to search for new technologies to solve the problems. The emergence of ISDN immediately caused widespread concern in the industry. However, due to the obstacles of communication coordination and the influence of policy, ISDN did not begin to popularize in the whole world till the 90s. By the end of 1993, telecommunications from 22 European countries