xtend Calling LinesThe first generation of Electronic Switching System (IS) appeared in the early 1960's. But within a few years these were superseded by the system which reflected new concepts based on the combination of communications and computers. Over the same period, digital transmission techniques have also been greatly improved.Computer control of exchanges, time divisions switching and the transmission of information in digital form are the basis for the successful large scale telecommunications connections throughout Korea. The recent development of microelectronics, space and optical fiber technologies made it possible to spread new telecommunications services around the world. Besides voice and text, huge quantities of visual information are being transmitted. Videotex systems connect subscribers to data banks and display economic, financial and scientific information as text or graphics on a television screen. In addition, services such as video-conferencing, teletex and electronic mail are widespread. All of these services could be integrated into a single global network called Integrated Services Digital Network (ISDN). An ISDEN comprises digital switching, computer control and optical fiber digital transmission.Telecommunications network consist of subscriber terminals, subscriber lines, local exchanges, toll exchanges and interexchange circuits.Subscriber terminals have evolved from the simple telephone set designed to provide basic voice telephony. The current trend is toward increasing intelligence in the terminal, enabling subscribers to perform a range of functions which enhance the telephone utility. The terminals associated with other services such as facsimile and data have also become more versatile and sophisticated. Already the concept is emerging of a multipurpose terminal for text, data and other non telephone services as well as being used as a telephone. An ordinary telephone line will be able t...
