History Column: Hedy Lamarr
Hedy Lamarr (born Hedwig Eva Maria Kiesler, 1914, in Vienna) is best known as a Hollywood actress of the 1940s and 1950s, starring in movies which included Boom Town (1940) with Clark Gable and Spencer Tracy, The Heavenly Body (1944), and Samson and Delilah (1949) opposite Victor Mature.
Her early acting career was in Germany, but in 1938 she moved to Hollywood via London, signed up by Louis B. Mayer of Metro-Goldwyn-Mayer (MGM). She was married (and divorced) six times. She was honoured in 1960 with a star on the Hollywood Walk of Fame for her contribution to the motion picture industry, and she died in January 2000 at the age of 85.
Less well known is the fact that she was also a talented and innovative inventor. In 1942, she and avant-garde musician and inventor George Antheil developed and patented a communications scheme for use in a radio guidance system for torpedoes. The key novelty was that this exploited frequency-hopping both so as not be discovered by an opponent and as a counter to jamming, and this may be considered as a forerunner of spread-spectrum techniques which are now widely used in secure communications. An important aspect of this was the means used for synchronisation of the hopping codes at the transmitter and receiver, which was achieved in a similar way to that used by Antheil to synchronise two pianos whose tunes were controlled by perforated paper strips. The figure below shows a page from the patent. In the top diagram can be seen seven switched capacitors which determined the seven frequencies of the hopping pattern.
A page of drawings from Lamarr and Antheil's patent (1942).
Acknowledgement:
The authors thank Dr E Detoma and Dr S. Maddio for the useful exchange of additional information on the subject.
Further information may be found at:
Richard Rhodes, Hedy's Folly: The Life and Breakthrough Inventions of Hedy Lamarr, Doubleday, New York, 2012.
"A Tale of Two Lives" https://physicsworld.com/a/a-tale-of-two-lives/, August 2018.
Alice George, Smithsonian Magazine, April 2019, https://www.smithsonianmag.com/smithsonian-institution/thank-world-war-…
Bombshell: The Hedy Lamarr Story, feature documentary, 2017 https://www.youtube.com/watch?v=BKXAkITImGU (trailer)
The technique was not exploited directly, but was employed by the US Navy in 1957 as part of the radio link for a sonobuoy. Lamarr and Antheil were posthumously inducted into the US National Inventors Hall of Fame in 2014.
Written by Hugh Griffiths and Alfonso Farina