Hedy Lamarr's Hidden Workbench

Hedy Lamarr was one of the best known film actresses of the 1930s and 1940s. Studios sold her as a beautiful face, and interviewers rarely asked her about anything else. In private she kept a small workbench in her home and spent evenings sketching inventions.

Before she left Europe she had been married to an arms manufacturer, and she had sat through years of business dinners about weapons. She had listened. One problem stayed with her: a radio-guided torpedo could be pushed off course if an enemy jammed the single frequency that carried its orders.

With the composer George Antheil she worked out an answer. Instead of one steady frequency, the transmitter and the torpedo would hop together through a changing sequence of frequencies, in step, like two players reading the same roll of music. An enemy listening on one channel would catch only a fragment.

They received a patent in 1942. The Navy did not use it. Decades later, related ideas, spreading a signal across many frequencies, became ordinary in wireless communication, and Lamarr was finally known as an inventor and not only as a face.