The Byzantine beacon system was a semaphore developed in the 9th century during the Arab–Byzantine wars. The Byzantine Empire used a system of beacons to transmit messages from the border with the Abbasid Caliphate across Asia Minor to the Byzantine capital, Constantinople. The main line of beacons stretched over some with stations placed from to . A message could be sent along the line in approximately one hour. A bonfire was set at the first beacon and transmitted down the line to Constantinople.