Development direction of telephone network

The telephone network has experienced the development process from the artificial network of manual exchange to the automatic network of automatic exchange, and also the evolution from the analog telephone network to the integrated digital telephone network. Compared with analog telephone network, digital telephone network has more advantages in communication quality, service type, service provided for non-telephone service network and automatic control and management of maintenance and operation. The development direction of telephone network is to realize integrated service digital network (ISDN), broadband integrated service digital network (B-ISDN) and personal communication network (UPT). By then, the telephone network will not only be a network for transmitting telephone information, but also provide services such as images and data according to users' requirements. Personal communication network will change the traditional way of communicating with each other only in fixed places, and individuals can communicate with any individual at any place and at any time.

The current development direction of telephone network is program-controlled digital network, that is, program-controlled private branch exchanges are installed in exchange centers at all levels, and the transmission circuits are all digital circuits. Program-controlled digital network is developing rapidly with its excellent communication quality and high automation. At present, the degree of digitization of program control in China has reached more than 85%. The next development direction of telephone network is to realize narrowband integrated services digital network (N-ISDN) and broadband integrated services digital network (B-ISDN).