Digital transmission in the local network

The local network has evolved for the conveyance of speech-band signals in an efficient manner. Fortuitously, this network can also carry higher frequency signals, although with some restrictions. The advent of modern semiconductor technology has allowed engineers to exploit these higher frequencies to provide additional services. Initially these additional services were generally restricted to analogue pair-gain and alarm systems but, with the birth of the information technology age, the capability of the local network to carry high-speed digital signals is being exploited. From a review of the characteristics of the local network and an assessment of its ability to carry digital signals a perception of the future evolution of the local network and the likely penetration of digital systems emerges.