This section is from the book "Bepler's Handy Manual of Knowledge And Useful Infomation", by David Bepler. Also available from Amazon: Bepler's Handy Manual of Knowledge and Useful Information.
One whistle signifies "down brakes." Two whistles signify "oft brakes." Three whistles signify "back up." Continued whistles signify "danger," Rapid short whistles "a cattle alarm." A sweeping parting of the hands on a level with the eyes, signifies "go ahead." Downward motion of the hands with extended arms signifies "stop." Beckoning motion of one hand signifies "back." Red flag waved up the track, signifies "danger." Red flag stuck up by the roadside, signifies " danger ahead." Red flag carried on a locomotive, signifies " an engine following." Red flag hoisted at a station, is a signal to "stop." Lantern at night, raised and lowered vertically, is a signal to " start." Lantern swung at right angles across the track is a signal to "start." Lantern swung in a circle signifies "back the train."