Phryctoria

Phryctoria (Greek: φρυκτωρία) was a semaphore system used in Ancient Greece.

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 the Athenians and asked for help by beacon-fires.

[5] The coding system was as follows: When they wanted to send the letter O (omicron), they fired five torches on the right set and three torches on the left set.