Etching of Armstrong (1890-1954) who was born in New York City and studied at Columbia University where he invented the regenerative circuit. This which was the first amplifying receiver and reliable continuous-wave transmitter. In 1918, he devised the superheterodyne circuit, which provided a highly selective means of receiving, converting and amplifying weak, high-frequency electromagnetic waves. Finally, in 1933, he invented the wide-band frequency modulation radio transmision system (now known as FM radio), which he perfected, virtually eliminating interference problems from static. Published by the International Telecommunication Union, (1955-1964).
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