Today in Germany, Austria and Switzerland it is Inventors’ Day (Tag der Erfinder). November 9th is celebrated as the holiday because it is the birthday of the actress Hedy Lamarr. She invented frequency-hopped spread spectrum in 1942.
The most celebrated invention of frequency hopping was that of actress Hedy Lamarr and composer George Antheil, who in 1942 received U.S. Patent 2,292,387 for their “Secret Communications System”. This early version of frequency hopping used a piano-roll to change among 88 frequencies, and was intended to make radio-guided torpedoes harder for enemies to detect or to jam. The patent was rediscovered in the 1950s during patent searches when private companies independently developed Code Division Multiple Access, a civilian form of spread-spectrum.
For more on Hedy Lamarr, read Hedy’s Folly: The Life and Breakthrough Inventions of Hedy Lamarr, the Most Beautiful Woman in the World.