Telephone system: domestic:70% of exchanges now digital; existing copper subscriber systems now being enhanced with Asymmetric Digital Subscriber Line (ADSL) equipment to accommodate Internet and other digital signals; trunk systems include fiber-optic cable and microwave radio relay
international:satellite earth stations - 2 Intersputnik (Atlantic and Indian Ocean regions), 1 Intelsat, 1 Eutelsat
Definition: This entry includes a brief general assessment of the system with details on the domestic and international components. The following terms and abbreviations are used throughout the entry:
Africa ONE - a fiber-optic submarine cable link encircling the continent of Africa.
Arabsat - Arab Satellite Communications Organization (Riyadh, Saudi Arabia).
Autodin - Automatic Digital Network (US Department of Defense).
CB - citizen's band mobile radio communications.
cellular telephone system - the telephones in this system are radio transceivers, with each instrument having its own private radio frequency and sufficient radiated power to reach the booster station in its area (cell), from which the telephone signal is fed to a telephone exchange.
Central American Microwave System - a trunk microwave radio relay system that links the countries of Central America and Mexico with each other.
coaxial cable - a multichannel communication cable consisting of a central conducting wire, surrounded by and insulated from a cylindrical conducting shell; a large number of telephone channels can be made available within the insulated space by the use of a large number of carrier frequencies.
Comsat - Communications Satellite Corporation (US).
DSN - Defense Switched Network (formerly Automatic Voice Network or Autovon); basic general-purpose, switched voice network of the Defense Communications System (US Department of Defense).
Eutelsat - European Telecommunications Satellite Organization (Paris).
fiber-optic cable - a multichannel communications cable using a thread of optical glass fibers as a transmission medium in which the signal (voice, video, etc.) is in the form of a coded pulse of light.
GSM - a global system for mobile (cellular) communications devised by the Groupe Special Mobile of the pan-European standardization organization, Conference Europeanne des Posts et Telecommunications (CEPT) in 1982.
HF - high frequency; any radio frequency in the 3,000- to 30,000-kHz range.
Inmarsat - International Maritime Satellite Organization (London); provider of global mobile satellite communications for commercial, distress, and safety applications at sea, in the air, and on land.
Intelsat - International Telecommunications Satellite Organization (Washington, DC).
Intersputnik - International Organization of Space Communications (Moscow); first established in the former Soviet Union and the East European countries, it is now marketing its services worldwide with earth stations in North America, Africa, and East Asia.
landline - communication wire or cable of any sort that is installed on poles or buried in the ground.
Marecs - Maritime European Communications Satellite used in the Inmarsat system on lease from the European Space Agency.
Marisat - satellites of the Comsat Corporation that participate in the Inmarsat system.
Medarabtel - the Middle East Telecommunications Project of the International Telecommunications Union (ITU) providing a modern telecommunications network, primarily by microwave radio relay, linking Algeria, Djibouti, Egypt, Jordan, Libya, Morocco, Saudi Arabia, Somalia, Sudan, Syria, Tunisia, and Yemen; it was initially started in Morocco in 1970 by the Arab Telecommunications Union (ATU) and was known at that time as the Middle East Mediterranean Telecommunications Network.
microwave radio relay - transmission of long distance telephone calls and television programs by highly directional radio microwaves that are received and sent on from one booster station to another on an optical path.
NMT - Nordic Mobile Telephone; an analog cellular telephone system that was developed jointly by the national telecommunications authorities of the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden).
Orbita - a Russian television service; also the trade name of a packet-switched digital telephone network.
radiotelephone communications - the two-way transmission and reception of sounds by broadcast radio on authorized frequencies using telephone handsets.
PanAmSat - PanAmSat Corporation (Greenwich, CT).
SAFE - South African Far East Cable
satellite communication system - a communication system consisting of two or more earth stations and at least one satellite that provide long distance transmission of voice, data, and television; the system usually serves as a trunk connection between telephone exchanges; if the earth stations are in the same country, it is a domestic system.
satellite earth station - a communications facility with a microwave radio transmitting and receiving antenna and required receiving and transmitting equipment for communicating with satellites.
satellite link - a radio connection between a satellite and an earth station permitting communication between them, either one-way (down link from satellite to earth station - television receive-only transmission) or two-way (telephone channels).
SHF - super high frequency; any radio frequency in the 3,000- to 30,000-MHz range.
shortwave - radio frequencies (from 1.605 to 30 MHz) that fall above the commercial broadcast band and are used for communication over long distances.
Solidaridad - geosynchronous satellites in Mexico's system of international telecommunications in the Western Hemisphere.
Statsionar - Russia's geostationary system for satellite telecommunications.
submarine cable - a cable designed for service under water.
TAT - Trans-Atlantic Telephone; any of a number of high-capacity submarine coaxial telephone cables linking Europe with North America. telefax - facsimile service between subscriber stations via the public switched telephone network or the international Datel network.
telegraph - a telecommunications system designed for unmodulated electric impulse transmission.
telex - a communication service involving teletypewriters connected by wire through automatic exchanges.
tropospheric scatter - a form of microwave radio transmission in which the troposphere is used to scatter and reflect a fraction of the incident radio waves back to earth; powerful, highly directional antennas are used to transmit and receive the microwave signals; reliable over-the-horizon communications are realized for distances up to 600 miles in a single hop; additional hops can extend the range of this system for very long distances.
trunk network - a network of switching centers, connected by multichannel trunk lines.
UHF - ultra high frequency; any radio frequency in the 300- to 3,000-MHz range.
VHF - very high frequency; any radio frequency in the 30- to 300-MHz range.
Source: CIA World Factbook - Unless otherwise noted, information in this page is accurate as of April 17, 2000