What are the exact words which the narrator uses to greet the signalman?

When the narrator arrives in the vicinity of the signal box, he greets the signalman with the following words:

"Halloa! Below there!"

On hearing these words, the signalman does not look up towards the narrator, as expected, but looks down the line. This causes the narrator to repeat the words and, this time, he is acknowledged by the signalman.

While these words may appear ordinary, they are, in fact, significant to the signalman. Later in the story, for instance, he reveals that he heard those exact words on "one moonlight night." The figure, to whom the voice belonged, appeared to be warning him about an impending accident, but it suddenly disappeared.

Six hours later, however, there was indeed an accident on the line in which numerous people were killed or wounded. For the signalman, then, these words are synonymous with that strange warning, and this causes him to be extremely wary of the narrator.