It is not the letter B, but the general alarm signal on the railway - long and three short... You can also signal with the letter C" - three short - the signal to the train to get back...

I wonder who of the authors of this council was driving in the locomotive cabin? Sound insulation, which allows you not to shake up from the noise of the engine, will easily protect the ears from the sluggish bips of the clutch, and at the distance where the driver will hear them, the driver in the car will only cross and have time.