telephone and telegraph service over wire and radio systems between correspondents located at great (virtually unlimited) distances from each other. The term “long-distance communications” arose in the technology of transmission of electrical signals over wire communications lines; a synonym is “intercity communications,” and an antonym is “local communications” (within a city or raion).
Telephone, telegraph, phototelegraph, and television signals are transmitted simultaneously over long distances over air, cable, and radio communications lines in which hundreds or thousands of independent communications channels are formed by multiplexing communications lines. The use of artificial earth satellites for long-distance communications is promising. To compensate for signal attenuation, attended and unattended (remote-controlled) repeater stations or relay stations with amplifiers for the transmitted signals are installed on some sections of long-distance ground lines. For deep-sea (cable) long-distance communications unattended repeaters with long service life are installed at certain intervals along the length of the cable. Reliable continuous communications are ensured by the use of standby equipment and automated long-distance communications lines.
N. M. IZIUMOV