The hydraulic telegraph and the ancient…sms

Only one night needed to transmit the message of the Fall of Troy to Mycenae despite the 550 kilometers separating the two glorious states. The news traveled through successive fire signals (beacons) with a pre-agreed message between Agamemnon and Clytemnestra, the royal couple of Mycenae. The occurrence refers to Aeschylus tragedy “Agamemnon” (5th century B.C.) and is the oldest mention in that ancient form of telecommunication. The play also describes in detail all of the mountainous beacons that reported the occurrence: Ida (south of Troy), mount Hermes (in Lemnos), Athos, Makistos mount (in Chalkis), Messapion (in Boeotia), mount Kithairon, Mount Aigiplankton (in Megara) to Mount Arachnaion (in Mycenae).

Replica of the hydraulic telegraph of Aeneas Tacticus and indicative messages in periods of war operations. OTE Group Telecommunications Museum.

But what happened in unpredictable situations in which it was impossible to have a pre-agreed message? This weakness was overcome by the hydraulic telegraph invented by Aeneas Tacticus of Stymphalus, in the middle of the 4th c. B.C. The new mechanism was able to transmit a large amount of pre-agreed messages. If you visit the OTE Group Telecommunications Museum in Athens, the signs that have been placed in the hydraulic telegraph replica give an idea of the context of those messages: "enemy in sight", "cyclical movement", "infantry in action", “King's Arrival”, "cease fire", " release of hostages", "misleading signals", "front-attack” ,"pestilence bout" and so on.

Map with the most well – known telecommunication group of beacons in ancient Greece. OTE Group Telecommunications Museum.

How did it work
How was and how did the hydraulic telegraph work? His description was rescued by the historical Polybius (2nd century B.C.), who says that there were identical cylindrical containers in all stations. From a tap on their base, the containers filled up to the same point with water. A cork floated on the surface of the water, on which a wooden stick was mounted vertically, carrying the pre-agreed messages.

"The successful transmission of the pre - agreed messages by the hydraulic telegraph of Aeneas Tacticus, used on war periods, was based on the absolute simultaneity between the transmitter and receiver operators

“Peltasts in action”, “retreat”, “alarm”. Indicative messages sent with the hydraulic telegraph during war. OTE Group Telecommunications Museum.

The system was based on the absolute simultaneity between the transmitter and receiver operators, who had to be very careful not to send the wrong message, which would be disastrous during wars. Every time a message had to be transmitted, the sender raised a lit torch, marking the simultaneous opening of the taps and waiting for a response. As soon as the receiver turned on its own torch, the two operators opened the tap at the same time. When the water level reached the height that corresponded to the desired message, with the same procedure of the torches, the transmitter informed the receiver to close his cork.

Information: Permanent exhibition of OTE Group Telecommunications Museum, 25 Proteos str., Nea Kifissia, https://www.otegroupmuseum.gr/portal

Exhibition "IDEA - Ancient Greek Science and Technology", Cultural Center “Hellenic Cosmos”, 254 Pireos str, Tavros, www.hellenic-cosmos.gr

View of the exhibition “"IDEA - Ancient Greek Science and Technology" hosted on the Cultural Center “Hellenic Cosmos”. In the foreground there is a replica of the Aeneas Tacticus hydraulic telegraph.

A museum and an exhibition
That brilliant method for the prompt messages transmission knew a greatly use in the enormous empire created by Alexander the Great. Those who want to learn more about both the mechanism and telecommunications in Greece is worth to visit the OTE Group Telecommunications Museum, where its replica is exhibited along with a wealth of information material. A replica of the hydraulic telegraph is also exhibited in the exhibition "IDEA - Ancient Greek Science and Technology" organized by the Foundation of the Hellenic World and the Science Center and Technology Museum NOESIS hosted on Cultural Center "Hellenic Cosmos" until October 2018.

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