国际电报电话咨询委员会(CCITT)第十八研究组专门研究综合业务数字网(ISDN)。随着数字通信技术的发展采用数字传输和数字交换的综合数字网已受到重视,並向综合业务数字网的方向发展。综合数字网(IDN)是用数字信号传输並采用数字交换的全数字网。在综合数字网中,数字交换和数字通道用于电话,数据传真等各种业务称为综合业务数字网。目前由于电信业务的发展和电子技术的进步,如数字电话网,公共数据网,计算机通信网,电报数据网等各种公用和专用电信网已迅速发展起来,而且随着电子技术的进一步发展和各种新型电信业务的出现,要求经济合理地共享通信网路,这就促进了综合业务数字网的发展, The eighteenth Study Group of the International Telegraph and Telephone Consultative Council (CCITT) specializes in Integrated Services Digital Networks (ISDN). With the development of digital communication technology, the integrated digital network using digital transmission and digital exchange has drawn great attention and has moved towards the integrated service digital network. Integrated Digital Network (IDN) is a digital network using digital signal transmission and digital switching. In the integrated digital network, digital switching and digital channels for telephony, data faxing and other services called Integrated Services Digital Network. At present, due to the development of telecommunication services and advances in electronic technology, various public and private telecommunication networks such as digital telephone network, public data network, computer communication network and telegraph data network have been rapidly developed. With the further development of electronic technology and The advent of various new types of telecommunication services requires the economical and reasonable sharing of communication networks, which has promoted the development of integrated services digital networks,