The invention of the Audion tube is credited to which inventor?

• A. Lee De Forest
• B. Reginald Fessenden
• C. Guglielmo Marconi
• D. Samuel Morse

Answer: (A)

The main idea is that the Audion opened the door to signal amplification in radio by adding a grid to a vacuum tube, creating the first practical amplifier. Lee De Forest is the inventor who made this breakthrough with the Audion around 1906, turning a simple detector into a device that could amplify weak electrical signals. This amplification was key for making receivers more sensitive and for driving transmitters, which enabled longer-range radio communication and the early growth of broadcasting. The leap came from introducing the control grid between the cathode and anode, allowing small changes in grid voltage to produce large changes in plate current. Before this,—like the Fleming valve with just two elements—there was no built-in amplification. Reginald Fessenden contributed important early radio experiments, especially with voice transmission, but he did not invent the Audion. Guglielmo Marconi advanced wireless telegraphy, and Samuel Morse invented the telegraph and Morse code.