tion 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.

Telephones - main lines in use: This entry gives the total number of
main telephone lines in use.

Telephones - mobile cellular: This entry gives the total number of
mobile cellular telephone subscribers.

Television broa