Reginald Fessenden

Reginald Aubrey Fessenden was a Canadian-born electrical engineer who pioneered amplitude-modulated radio broadcasting. On December 23, 1900, he achieved what is regarded as the first transmission of speech by radio, sending a message roughly a mile across a test site, and he patented the heterodyne principle for receiving radio signals in 1905. In January 1906 he achieved the first two-way transatlantic radiotelegraph exchange, and by Christmas Eve that year he is credited, though the claim remains debated among historians, with an early radio broadcast of voice and music for a general audience. Beyond radio, he invented the beat-frequency oscillator and the hot-wire barretter for receiving weak signals, and developed the Fessenden oscillator, an underwater electromechanical transducer that became foundational to sonar. He held more than 500 patents across fields including reflection seismology and television apparatus, and received the Institute of Radio Engineers Medal of Honor in 1921.