综合业务数字网（ＩＳＤＮ），通常指窄带ＩＳＤＮ，即“一线通”，是一种７０年代在电话综合数字网（ＩＤＮ）的基础之上发展起来的技术。在ＩＤＮ中话音和图像等模拟信号要进行模拟／数字变换后才能进行传输，在接受端也要进行数字／模拟反变换才能进行通信。而ＩＳＤＮ是以 Integrated Services Digital Network (ISDN), often referred to as narrowband ISDN, is a “line-by-line” technology that evolved over the telephone integrated digital network (IDN) in the 1970s. IDN in the voice and images and other analog signals to be analog / digital conversion before transmission, the receiver must also carry out digital / analog inverse transform to communicate. The ISDN is