[skimoose]

Morse code was used heavily by the railroads, but there was another signaling system that was also employed by railroads which was expressed in dashes and ohs or dots. That was the system of train whistle (or in the diesel age air horn) blasts. This is not just the engineer having fun, the sequence of long and short blast has meaning.

Here's the North American system, other parts of the world use different signals.

Sequence What it means:
Succession of short sounds Used when an emergency exists, or if persons or livestock are on the track.
– When train is stopped. The air brakes are applied and pressure is equalized.
– – Train releases brakes and proceeds.
o o Acknowledgment of any signal not otherwise provided for.
o o o When train is stopped: means backing up, or acknowledgment of a hand signal to back up.
o o o o Request for a signal to be given or repeated if not understood.
– o o o Instruction for flagman to protect rear of train.
– – – – Flagman return from the west or south.
– – – – – Flagman return from the east or north.
– – o – Train is approaching public grade crossing(s). This is known as Rule 14L in almost all railroad operating rules.
– o Inspect the brake system for leaks or sticking brakes.

Dave says All aboard!