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Much more than just a pretty face

5/10/2020

 
Picture
​Hedy Lamarr was one of the most provocative film stars of Hollywood’s golden age. She also invented something in 1942 that the average person uses all the time and carries with them everywhere they go.

Hedy Lamarr was about as far from the image of a technical innovator and inventor as one could expect. A 1930’s and 40’s starlet, she graced movie screens with the likes of Spencer Tracy and Clark Gabel. Despite such a busy filming schedule, Hedy Lamarr still had time to invent what is now known as Spread Spectrum Frequency Transmission.

It’s very easy to interfere with a transmitter that sits on the same frequency. In World War II this had serious implications for radio communications. All the enemy had to do was find the frequency the Allies were on and jam it, or they could quietly eavesdrop and collect intelligence data.

But if the transmitter constantly changes frequencies, and the receiver changes with it, then the transmission is much more secure because it never stays on any one channel for very long. It would be impossible for the enemy to follow the constant changes.
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That’s basically how spread spectrum frequency transmission works. Hedy Lamarr, along with a musician neighbor, came up with a device that used something like paper piano rolls to change the frequencies. If both the transmitter and receiver had copies of the same roll, and the rolls were running exactly in sync, the system would work. The paper rolls were a 1940’s version of “software.”

Lamarr was granted a patent on August 11, 1942.

As things went, the US Navy took a pass on Hedy Lamarr’s invention until 1962 when the Cuban Missile Crisis forced the American military to up their technological game. By then the patent had expired but Lamarr’s legacy was secure.

Today, cellphones, wifi, Bluetooth, remote controlled devices, security alarms, public safety communications systems…almost everything wireless uses some form of spread spectrum. The frequency hopping is controlled by computers instead of paper rolls and occurs thousands of times per second. The net result is less interference and more security.

Hedy Lamarr died in 2000, just about when cellphones became an everyday item and well before Bluetooth or wifi.

[Source: Chris Warren]
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