Plural of signal; transmitted information, signs, or indicators used to convey messages or data. Can refer to electrical impulses, radio waves, or any form of communication medium.
From Latin 'signum' meaning 'mark' or 'sign', through Old French 'signal'. Originally referred to military or nautical flag communications before expanding to include all forms of transmitted information.
The first transatlantic radio signal—just the Morse code letter 'S'—was transmitted by Marconi in 1901, but many scientists thought it was impossible due to Earth's curvature. They didn't yet understand that radio waves could bounce off the ionosphere, effectively bending around the planet.
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