Phryctoria

Phryctoria was a semaphore system used in Ancient Greece. The phryctoriae were towers built on selected mountaintops so that one tower would be visible to the next tower. 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. 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.
When Cnemus attacked Salamis Island, the Salaminians informed the Athenians and asked for help by beacon-fires.
Polybius wrote that Pyrsourídas were beacons established by Perseus of Macedonia across the entire region, enabling him to receive rapid reports about events in different locations. The Byzantine encyclopedia Suda notes that this system was similar to the later Byzantine beacon network.

Phryctoriae and Pyrseia

Ιn the 2nd century BC, the Greek engineers from Alexandria, Cleoxenes and Democletus invented the pyrseia. 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, 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.
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, they fired five torches on the right set and three torches on the left set.
File:Replica of fire signals and beacons, Kotsanas Museum of Ancient Greek Technology.jpg|thumb|A small reconstruction of fire signals and beacons in Museum of [Ancient Greek Technology|Kotsanas Museum of Ancient Greek Technology], Athens, Greece.