Steam whistle

The main purpose of railway signaling systems is to manage circulation and guarantee the necessary safety conditions for the movement of trains.
Steam locomotives are equipped with a low-pitched or high-pitched horn, depending on their series. The locomotive's horn is placed at the top of the boiler and is operated by a lever that opens the steam outlet valve and allows sound projection.
Through the hiss of the locomotives, with a shorter or longer ring, the driver can indicate that the train is going to move forward or backward, or that the locomotive's brakes must be tightened or widened. In an alarm situation, it warns acoustically of a dangerous situation.