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Updated: May 18, 2025
The ancients had evolved systems by which any word could be spelled, but they did not seem to be able to apply them practically to their primitive heliographs. An application of sound-signaling was worked out for Alexander the Great, which was considered one of the scientific wonders of antiquity.
There is another form of sound-signaling which, though it has been developed in recent years, may properly be mentioned in connection with earlier signal systems of similar nature. This is the submarine signal. We have noted that much attention was paid to communication by sound-waves through the medium of the air from the earliest times.
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