Kathryn Coldham explains the science behind Hedy Lamarr’s ground-breaking invention of the ‘Frequency-Hopping Spread Spectrum’ (FHSS) used in modern Wi-Fi and Bluetooth technology and the place of the woman inventor in both the 1940s and contemporary society.
Hedwig Eva Maria Kiesler – who was better known by her stage name, Hedy Lamarr – entered the public eye for being an Austrian and American actress during the Golden Age of Hollywood. Born in 1914 in Vienna, she became a Hollywood actress in the late 1930s after meeting the head of MGM, Louis B. Mayer, in Paris. Lamarr had a successful acting career, working alongside the likes of Clark Gable and Judy Garland, but her lesser known pursuit is one that allowed her to change the world – Lamarr was an inventor!
Primarily self-taught, her inquisitive mind led to her devising many inventions and ideas. She presented her sketches of plane wings to businessman and pilot Howard Hughes, in order to make planes travel faster. This was after she independently studied the aerodynamics of birds and the different shapes of fish.
Her big invention came during the Second World War. Lamarr and her friend, Dr George Antheil – a composer and pianist – came up with the idea of creating a frequency hopping signal that could be used to guide radio-controlled torpedoes, without this signal being tracked or intercepted.
A frequency hopping signal is a device that transmits a radio signal by alternating between different frequencies – a term used to describe the number of radio waves that are sent out per second. This alternation is carried out in a random sequence that is known to both the sender and the receiver of the signal, making it impossible for the signal to be overridden and the torpedo to be hijacked.
What made their idea so unique was that Lamarr and Antheil theorised that paper player piano rolls could be used to alternate and control the frequency. These are a type of data storage medium used to operate a player piano – a piano that is programmed to play by itself! The piano rolls contain tiny holes punched into them, each giving rise to a different musical note. A ‘tracker bar’ is used to read the paper so, when the bar passes over a particular hole, its corresponding note is played. This allowed for a series of notes to be pre-determined and played, just as a series of frequencies could be pre-assigned to a signal before it is transmitted or received.
The frequency hopping signal received its patent in 1942 but the invention was not used by the US military since Lamarr and Antheil were not military staff; however, a version of their design was used on US Navy ships during the Cuban Missile Crisis. During the war, Lamarr also wanted to assist the war effort by joining the National Inventors Council, but was turned away and it was suggested that she should use her celebrity status to sell war bonds instead.
Lamarr did not receive recognition for her work until 1997, when she and Antheil received the Electronic Frontier Foundation Pioneer Award. Today, their invention is known as ‘Frequency-Hopping Spread Spectrum’ (FHSS) and is used in modern Wi-Fi and Bluetooth technology – this led to Lamarr and Antheil posthumously becoming members of the National Inventors Hall of Fame in 2014.
At present, female inventors are massively under-represented: for example, in 2016, the country the with largest proportion of female inventors was Russia, at just 15.7% [1.], while the country with the lowest was Japan, with only 3.7%[1.] of its inventors being female. Meanwhile, in Great Britain, 7.3%[1.] of the inventor-workforce were female. There has been some improvement over recent years – including in the UK, where the proportion of female inventors has increased by 16% in the past decade[1.] – but, there is still a long way to go.
Kathryn is an undergraduate physics student at Queen Mary University of London. She has previously worked at CERN and aspires to becoming a particle physicist and a science communicator, to help investigate the building blocks of our universe while inspiring the next generation of physicists.[1.] https://www.gov.uk/government/news/female-inventorship-on-the-rise-worldwide