A torpedo that changed radio channels
A radio-controlled torpedo had a vulnerability: if an enemy transmitted a strong signal on the same frequency, it could drown out the command telling the torpedo where to go. This is called jamming. Hedy Lamarr and composer George Antheil proposed a way to make that interference harder: have the sender and torpedo switch frequencies together, rapidly and according to a shared pattern.
A jammer tuned to one frequency might then lose the signal as it moved elsewhere. To keep the command readable, however, both ends had to make the same changes at precisely the same moments. A receiver that missed the pattern would lose contact with the torpedo.
A composer’s machine becomes part of the design
Their 1941 patent described using synchronized, perforated rolls—much like those that control player pianos—to determine when the radio would change frequencies. The rolls could encode a sequence of changes known to both transmitter and receiver. Antheil’s experience with mechanical music systems helped shape this unusual approach to a communications problem.
The key idea was not simply to use many frequencies. It was to make the signal move in a coordinated, unpredictable-to-an-outsider sequence, so an enemy would have a harder time keeping its interference in step.
Why the idea waited
The U.S. Navy did not put the patented system to use during World War II. Its mechanical synchronization scheme was difficult to fit into practical military equipment of the time, and the patent did not become a wartime torpedo system. The underlying principle—coordinated frequency changes to resist interference—became more practical as electronic components improved.
Lamarr and Antheil’s proposal was an early example of frequency hopping, a technique later used in various radio systems. It was not the direct blueprint for every modern wireless technology, but it showed how a signal could protect itself by refusing to stay in one place on the dial.
