Born Aug 26 1873 - Died Jun 30 1961
Space Telegraphy Radio
Patent Number(s) 879,532
In the early 1900s, the great requirement for further development of radio was an efficient and delicate detector of electromagnetic radiation. Lee de Forest provided that detector. DeForest found a clue to creating the long-sought detector of electromagnetic radiation in John A. Fleming's invention of the so-called electronic valve. The most serious drawback of the Fleming valve was that it was relatively insensitive to changes in the intensity of incident electromagnetic radiation. Moreover, the Fleming valve could act only as a rectifier, not an amplifier. DeForest's simple but revolutionary answer was to insert a third electrode between the cathode and the anode. The audion amplifier was the most important of de Forest's more than 300 patents.
DeForest’s audion was used for many different purposes such as a detector for radio signals, an amplifier of audio, and an oscillator for transmitting currents. The Audion was used to transmit radio waves from radio frequency (RF) to audio frequency (AF). This allowed radio waves to be heard through headphones or even broadcast via loudspeaker. The audion has been most famously used in long-distance telephone service as it enables sound to travel over wireless communication systems. DeForest’s audion vacuum tube was the key component of all radio, telephone, radar, television, and computer systems before the invention of the transistor in 1947.