Actress Hedy Lamar Invents Radio Frequency Hopping During WWII

Actress Hedy Lamar received a patent on August 11, 1942 for inventing a secret way of guiding torpedoes against the Nazi U boats that were wrecking havoc on the allies.

"Frequency hopping."

The American Physical Society has the story.

Legend has it that Lamarr approached him for endocrinological advice, but the two soon began chatting about weapons, particularly radio-controlled torpedoes and how to protect them from jamming or interference. She realized that “we’re talking and changing frequencies” all the time, and that a constantly changing frequency is much harder to jam.

This became the basis for their design for a torpedo guidance system. Lamarr contributed the idea of frequency hopping, while Antheil drew on his experience with “Ballet Mécanique” and the sixteen player pianos to devise a means of synchronizing the rapidly changing radio frequencies envisioned by Lamarr. Their joint invention used a mechanism similar to piano player rolls to synchronize the changes between the 88 frequencies–not coincidentally, this is also the standard number of piano keys–and called for a high-altitude observation plane to steer a radio-controlled torpedo from above. They submitted their patent on June 10, 1941, and the patent was granted on August 11, 1942.

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