: Since the 19th century, the College of Cardinals has used smoke to announce election results: black smoke indicates a failed vote, while white smoke signals a new pope. Core Signaling Language
: The earliest recorded use dates to the 8th century BC. Soldiers along the Great Wall of China used smoke to signal imminent danger or enemy movements. 1 : Smoke Signal
Because signals were visible to everyone, including enemies, meanings were often pre-arranged between specific senders and receivers to maintain secrecy. However, several general codes became common: : Since the 19th century, the College of