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    Hedy Lamar's Patent

U.S. 2,292,397, issued August 11, 1942

On the eve of the Second World War, glamorous actress Hedy Keisler Markey (Hedy Lamar) and avant garde composer George Antheil invented a form of secure wireless communication, frequency hopping spread spectrum (FHSS).

 The patent taught the use of synchronized piano rolls at transmitter and receiver to shift the frequency of a broadcast radio signal, the arbitrary shifts from one frequency to another preventing jamming or eavesdropping. The basic application was to control a torpedo (even though a piano roll in a torpedo does seem rather far-fetched), so the breaks as the system shifted from one frequency to another were not important.

 While never adopted by the military during the life of the patent, today, sixty years after its invention, FHSS has become an important wireless communications protocol, used especially in local area wireless networks, where the data signal is modulated with a narrowband carrier signal that "hops" in a random but predictable sequence from frequency to frequency as a function of time over a wide band of frequencies.