Phryctoria

Phryctoria (Greek: φρυκτωρία) was a semaphore system used in Ancient Greece. The phryctoriae were towers built on selected mountaintops so that one tower (phryctoria) would be visible to the next tower (usually 20 miles away). The towers were used for the transmission of a specific prearranged message. One tower would light its flame, the next tower would see the fire, and light its own.

In Aeschylus tragedy Agamemnon, a slave watchman character learns the news of Troy's fall from Mycenae by carefully watching a fire beacon.^[1]^[2] Thucydides wrote that during the Peloponnesian War, the Peloponnesians who were in Corcyra were informed by night-time beacon signals of the approach of sixty Athenian vessels from Lefkada.^[3] When Cnemus attacked Salamis Island, the Salaminians informed they Athenians and asked for help by beacon-fires.^[4]

Phryctoriae and Pyrseia

Diagram of a fire signal using the Polybius cipher

Ιn the 2nd century BC, the Greek engineers from Alexandria, Cleoxenes (Greek: Κλεόξενος) and Democletus (Greek: Δημόκλειτος) invented the pyrseia (Greek: πυρσεία). Πυρσεία from πυρσός which means torch. The letters of the Greek alphabet were listed on a table. Each letter corresponded to a row and a column on the table. By using two groups of torches (five torches in every group), the left indicating the row and the right the column of the table, they could send a message by defining a specific letter through combination of light torches. ^[5]

The coding system was as follows:

	1	2	3	4	5
1	Α	Β	Γ	Δ	Ε
2	Ζ	Η	Θ	Ι	Κ
3	Λ	Μ	Ν	Ξ	Ο
4	Π	Ρ	Σ	Τ	Υ
5	Φ	Χ	Ψ	Ω

When they wanted to send the letter O (omicron), they fired five torches on the right set and three torches on the left set.

References

^ Aeschylus. Oresteia, Agamemnon (in Greek). p. 2. καὶ νῦν φυλάσσω λαμπάδος τό σύμβολον, αὐγὴν πυρὸς φέρουσαν ἐκ Τροίας φάτιν ἁλώσιμόν τε βάξιν500-400BC
^ Sommerstein, Alan H. (2009). Aeschylus. Oresteia: Agamemnon. Cambridge, MA: Loeb Classical Library, Harvard University Press. So now I am still watching for the signal-flame, the gleaming fire that is to bring news from Troy and tidings of its capture
^ Thucydides, Peloponnesian War, 3.80
^ Diodorus Siculus, Library, 12.49
^ Polybius. The Histories, Volume IV: Book 10 P. 46. Translated by W. R. Paton. Revised by F. W. Walbank, Christian Habicht. Loeb Classical Library 159. Cambridge, MA: Harvard University Press, 2011. "These torches having been lowered the dispatcher of the message will now raise the first set of torches on the left side indicating which tablet is to be consulted, i.e., one torch if it is the first, two if it is the second, and so on. Next he will raise the second set on the right on the same principle to indicate what letter of the tablet the receiver should write down"