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Optical communication system by Aeneas Tacitus, 4th century B.C.
Aeneas Tacitus, a Greek military scientist and cryptographer, invented an optical communication system that combines water and beacon telegraphy. Torches indicated the beginnings and the ends of message transmissions while water jars were used to transmit the messages. These jars had a plugged standard-size hole drilled on the bottom side and were filled with water. As those who sent and those who received the message unplugged the jars simultaneously, the water drained out. Because the transmitted messages corresponded to water levels, the sender indicated by torch signal that the appropriate water level has been reached. It is a disadvantage that the possible messages are restricted to a given code, but as this system was mainly used for military purposes, this was offset by the advantage that it was almost impossible for outsiders to understand these messages unless they possessed the codebook.
With communication separated from transportation, the distant became near.
Tacitus' telegraph system was very fast and not excelled until  the end of the 18th century.
For further information see Joanne Chang & Anna Soellner, Decoding Device,  http://www.smith.edu/hsc/museum/ancient_inventions/decoder2.html
 http://www.smith.edu/hsc/museum/ancient_inven...
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