Radio receiver crude triode, was invented in 1906 by Lee De Forest as a more sensitive detector for radio receivers, by adding a third electrode to the thermionic diode detector, the Fleming valve. It was not widely used until its amplifying ability was recognized around 1912. The first tube receivers, invented by De Forest and built by hobbyists until the mid 1920s, used a single Audion which functioned as a grid-leak detector which both rectified and amplified the radio signal. There was uncertainty about the operating principle of the Audion until Edwin Armstrong explained both its amplifying and demodulating functions in a
Harold Rosen (electrical engineer) him with hands-on experience with radio communications and the then-new field of radars. In 1949, Rosen married Rosetta, and they had two sons, Robert (born 1950) and Rocky (born 1966). Rosetta died in 1969. In 1984 he married Deborah Castleman, a satellite systems engineer also working at Hughes Aircraft Company. Rosen died on January 30, 2017 due to complications from a stroke, aged 90. Rosen has more than 80 patents. He was a Fellow of the IEEE and the AIAA, and a member of the National Academy of Engineering. Rosen has received numerous awards which include: Harold Rosen (electrical engineer)