Digital Communication

For most of the last 100 years of the 20th century the connection between the subscriber and their telephone exchange was copper twisted pair buried in the pavement or distributed overhead on poles. Given the enormity of the investment in this local loopinfrastructure it is hardly surprising that it had lasted for so long. However, by the late 1990s the convergence between voice, computer and television applications – and its inexorable move to digital-based technologies – had led to an erosion of demarcations.

For most of the history of fixed line telephony, the bandwidth that copper provided was some 3KHz, limited by analogue techniques and designed to be the cheapest solution that the telecomms operator could get away with. However, the twisted pair is inherently capable of much higher bandwidths and over short distances can carry video or broadband data. New technologies – such as ISDN and ADSL – were developed to enable higher performance to be delivered over the existing infrastructure. Innovation and competition was significantly helped by government action to end incumbent telecomms companies’ monopoly over the local loop.

In addition, the 1990s had seen cable companies investing massively in alternative connections to the home. Not all use the same technology, but the great majority have fibre optic cable to the curbside cabinet and coaxial cable from there to the home. In most cases these cable networks were installed to deliver television to the home and were designed on the basis of broadcast TV services. However, as much of the developed world continues its inexorable move towards broadband, their high bandwidth can be exploited to deliver other forms of digital-based services too.

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