Hedy Lamarr, the 1940s Hollywood Actress, Co-Invented the Frequency-Hopping Technology Behind Wi-Fi and GPS

Hedwig Eva Maria Kiesler — better known as Hedy Lamarr — was born in Vienna in 1914 and emigrated to Hollywood in 1937, where MGM cast her in a string of films opposite Clark Gable, Spencer Tracy, and Jimmy Stewart. The studio's marketing called her "the most beautiful woman in the world." What it did not advertise was that she had been working through her teens as an apprentice in a Viennese munitions firm owned by her first husband, Friedrich Mandl, who supplied weapons to fascist governments. She listened. She read. By the time she escaped to Paris in 1937, she had absorbed a working knowledge of guided-torpedo control systems.

The patent

In 1940, watching the early Battle of the Atlantic from afar and horrified that Allied torpedoes were being jammed by German radio countermeasures, Lamarr began sketching a solution. Her idea: don't send the radio control signal on a single fixed frequency. Instead, have the transmitter and receiver simultaneously hop between dozens of frequencies on a synchronized schedule that an enemy listener wouldn't know. Anyone trying to jam the signal would have to jam every frequency at once, requiring far more power than they could deliver.

She partnered with avant-garde composer George Antheil, who had years earlier written a piece called Ballet Mécanique that synchronized 16 mechanical player pianos. Antheil suggested using a similar punched-paper-roll mechanism — exactly like a piano roll — to control the frequency-hopping schedule on both ends. The two filed jointly for U.S. Patent 2,292,387, "Secret Communication System," granted on August 11, 1942.

The Navy says no

Lamarr donated the patent to the U.S. government for the war effort. The Navy filed it away. The reasoning, as later declassified memos suggested, was partly technological skepticism (the player-piano mechanism seemed mechanically fragile inside a torpedo) and partly institutional dismissal — a memo described the inventor as "the actress." The patent expired in 1959 without ever being used in combat.

The quiet conquest of every modern radio

By the 1960s, electronics had advanced to where Lamarr and Antheil's idea could be implemented in solid-state circuits rather than mechanical rolls. The U.S. military adopted frequency-hopping spread spectrum on the Sincgars combat radio in 1962. From there it migrated into civilian standards.

Today, every Bluetooth device on Earth uses frequency hopping to share the crowded 2.4 GHz band with Wi-Fi and microwaves. The U.S. military's JTIDS tactical data link uses it. GPS uses a related technique called direct-sequence spread spectrum derived from the same lineage. The 802.11 family of Wi-Fi standards uses spread spectrum techniques that descend directly from the Lamarr-Antheil patent.

Late recognition

Lamarr received almost no recognition for the invention during her lifetime. The Electronic Frontier Foundation gave her its Pioneer Award in 1997 — three years before her death at age 85. The National Inventors Hall of Fame inducted her in 2014. Austria celebrates an "Inventors' Day" on her birthday, November 9. By the time the Bluetooth Special Interest Group recognized her contribution officially in 2014, an estimated 3 billion devices using frequency-hopping descended directly from her patent were in active use worldwide.

"Any girl can be glamorous," Lamarr once said. "All you have to do is stand still and look stupid." She refused, throughout a 47-film career, to do the latter — and the proof is in your pocket.