Railroad Code of Whistle Signals Antique Original SignAs I tried to do some research into the history of railroad signals in order to date and to fully understand! this sign, I've realized it is a vast and complicated history I don't have enough knowledge, or patience, to dive deep into! I did learn that the use of train whistles seems to have originated in England in 1832, when a stationmaster suggested that the trains should have an audible signaling device, and thus a local musical instrument builder