一、技术可行性1．ISDN的国际标准和实施技术已经成熟70年代初CCITT提出ISDN的基本概念，具体规定了ISDN系统的设备、网络和业务的国际标准，80年代中后期ISDN技术进入试验阶段，90年代各国相继投入使用。ITU—T对其建议不断完善。在技术方面我国为建立ISDN已做了大量准备工作 First, the technical feasibility 1. ISDN international standards and implementation technologies have matured In the early 1970s, CCITT put forward the basic concept of ISDN, specifying the ISDN system equipment, networks and services in international standards. In the mid-to-late 1980s, ISDN technology entered the pilot phase. In the 1990s, various countries successively put into use . ITU-T constantly improves its recommendations. In terms of technology, China has done a lot of preparatory work to establish ISDN