Which invention did Hedy Lamarr and George Antheil patent in 1942 to help guide torpedoes?

Hedy Lamarr and George Antheil patented a frequency-hopping spread-spectrum communication system in 1942 to help guide torpedoes.

Their design used synchronized piano-roll mechanisms to make a transmitter and receiver rapidly switch among radio frequencies. The changing pattern was intended to prevent an enemy from jamming or intercepting the guidance signal. The patent was assigned to the United States Navy, although the Navy did not immediately adopt the system for wartime torpedoes.

Lamarr was a film actor and inventor, while Antheil was an avant-garde composer. Their idea did not directly create modern Wi-Fi or Bluetooth, but related spread-spectrum techniques later became important in secure and resilient wireless communications.

The common claim that Lamarr invented Wi-Fi is too broad. Her patent described a specific frequency-hopping concept, and later engineers developed the technologies used in modern wireless networks. The invention nevertheless demonstrated remarkable foresight about interference-resistant communication.