Overview

The term telecommunications generally refers to two-way transmission and reception of intelligent signals by wire and cable and through the air, as contrasted with the one-way transmission of radio and television broadcasting. It encompasses the transmission of voice, data, video, and facsimile (fax) signals from point to point over a frequency span from audio to microwaves. However, its primary focus is still on telephone communications that are carried by wire, coaxial, fiberoptic, and undersea cable, as well as terrestrial microwave and satellite relays, and cellular mobile telephone links.

The merging of computers and telephone networks has dissolved the boundary between the two technologies. The computer and telephone-line modem are vital for such services as fax, accessing the Internet, and for sending and receiving E-mail, but they are dependent on wire or cable links. Both the cordless and cellular mobile telephones depend on radio-frequency links, as do the pagers and handheld computers called personal communications devices (PCDs).

New concepts in telecommunications promise to keep the whole industry in a state of flux for many years to come. For example, fleets of commercial communications satellites have been lofted into earth orbit so that telephone calls can be made between any two locations on earth. Where alternative land lines exist, the lower-cost terrestrial links can be selected. The new low-altitude Iridium and Globalstar satellites are now competing for global telephone service business with the geosynchronous Inmarsat satellites.

The purchase of cable television companies by prominent long-distance multinational telephone service providers...