Lamarr's reputation as an inventor is based on her co-creation of a frequency-hopping system with
George Antheil. During World War II, Lamarr was inspired to contribute to the war effort, and focused her efforts on countering torpedoes. In her home, explains author
Richard Rhodes during an interview on CBS, she devoted a room to drafting her designs for frequency-hopping.
[20]
Lamarr and Antheil discussed the fact that radio-controlled torpedoes, while important in the naval war, could easily be jammed by broadcasting interference at the frequency of the control signal, causing the torpedo to go off course.
[21] Lamarr had learned something about torpedoes during her marriage to Mandl. Lamarr and Antheil developed the idea of using frequency hopping to avoid jamming. This was achieved by using a piano roll to unpredictably change the signal sent between a control center and the torpedo at short bursts within a range of 88 frequencies in the radio-frequency spectrum (there are 88 black and white keys on a piano keyboard).
The specific code for the sequence of frequencies would be held identically by the controlling ship and in the torpedo. It would be practically impossible for the enemy to jam all 88 frequencies, as it would require too much power. The frequency-hopping sequence was controlled by a player-piano mechanism.
On 11 August 1942,
U.S. Patent 2,292,387 was granted to Hedy Kiesler Markey, Lamarr's married name at the time, and George Antheil. Although novel, the idea was not implemented in the U.S. until 1962, when it was used by U.S. military ships during a
blockade of Cuba. Lamarr's work was honored in 1997, when the
Electronic Frontier Foundation gave her a belated award for her contributions.
[7]
Lamarr's and Antheil's frequency-hopping idea served as a basis for modern
spread-spectrum communication technology, such as
GPS,
Bluetooth,
COFDM (used in
Wi-Fi network connections), and
CDMA (used in some cordless and wireless cell phones).
[24] Blackwell, Martin, and Vernam's 1920 patent
[25] seems to lay the communications groundwork for Lamarr and Antheil's patent, which employed the techniques in the autonomous control of torpedoes.