It was a hydraulic telegraph created in the 4th century B.C. by the Greek Aeneas Tacticus.
It was designed to send long-distance messages for military purposes. The device had pre-arranged message to be sent across the empire of Alexander the Great.
These messages were, ‘enemy on sight’, ‘cavalry’, ‘we need wheat’, ‘infantry in action’, ‘cyclical movement’ etc.
These devices were placed on selected hills.
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