Lamarr, under the name Hedy Kiesler Markey, and composer George Antheil filed a U.S. patent application for a frequency-hopping torpedo guidance system.
On 10 June 1941, Hedy Lamarr — filing under her legal married name Hedy Kiesler Markey — together with avant-garde composer George Antheil, submitted a patent application to the United States Patent Office for a "Secret Communication System." The invention proposed a method of radio-guided torpedo control that used synchronized, rapidly switching radio frequencies — a concept now known as frequency hopping — to prevent enemy forces from jamming or intercepting the guidance signal.
The idea reportedly grew out of Lamarr's concern for Allied forces during World War II after learning about torpedoes being easily jammed. Drawing on her fascination with mechanics and her earlier exposure to munitions technology through her first husband, arms manufacturer Friedrich Mandl, she partnered with Antheil, who had experience synchronizing multiple player pianos, to develop a mechanism for synchronizing frequency changes using a piano-roll-like system.
This filing represents a landmark moment: a Hollywood film star, largely unrecognized for technical work at the time, contributing to a sophisticated wartime communications concept. Though the U.S. Navy did not adopt the technology during the war, the underlying principle would later become foundational to spread-spectrum communications, influencing technologies such as Wi-Fi, GPS, and Bluetooth decades later.
The filing stands as one of the earliest documented instances of a woman in entertainment simultaneously pursuing serious scientific and engineering innovation, challenging contemporary assumptions about the intellectual capacities of actresses.