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De Forest, Lee

(Encyclopedia)De Forest, Lee, 1873–1961, American inventor, b. Council Bluffs, Iowa, grad. Yale, 1896. He was a pioneer in the development of wireless telegraphy, sound pictures, and television. His triode (1906)...

radar

(Encyclopedia)radar, system or technique for detecting the position, movement, and nature of a remote object by means of radio waves reflected from its surface. Although most radar units use microwave frequencies, ...

European Southern Observatory

(Encyclopedia)European Southern Observatory (ESO), an intergovernmental organization for astronomical research with headquarters in Garching, near Munich, Germany. The ESO began in 1962 as a consortium among Belgiu...

SETI

(Encyclopedia)SETI sĕtˈē [key] [Search for ExtraTerrestrial Intelligence], name given to a series of independent programs to detect radio signals from civilizations beyond the solar system. Modern SETI efforts c...

broadcasting

(Encyclopedia)broadcasting, transmission, usually using radio frequencies, of sound or images to a large number of radio or television receivers. In the United States the first regularly scheduled radio broadcasts ...

short waves

(Encyclopedia)short waves, radio waves whose frequencies range from about 3 to 25 megahertz (Mhz), corresponding roughly to the high-frequency band (see radio frequency). When they impinge on certain layers of the ...

Paley Center for Media

(Encyclopedia)Paley Center for Media, American archive of radio and television programs, and forum for the discussion of the role and evolution of electronic media as well as the intersections of media and society;...

Saca González, Elías Antonio

(Encyclopedia)Saca González, Elías Antonio ālēˈäs äntōˈnēō säˈkä gōnsälˈās [key], 1965–, Salvadoran political leader, president of El Salvador (2004–9), b. Usulután. “Tony” Saca worked as...

audiovisual education

(Encyclopedia)audiovisual education, educational instruction by means of materials that use the senses of sight and hearing to stimulate and enrich learning experiences. The successful use of motion pictures and ot...

radar astronomy

(Encyclopedia)radar astronomy, application of radar to the determination of distances and planetary features within the solar system, such as rotation rates. A short burst of radio waves is transmitted in the direc...