The jingle of Swiss railway is a simple tritone. But: it is different for each of the three main languages (SBB doesn’t operate where Rumantsch is spoken). The abbreviation for each language is taken as notes, with E flat standing in for S because its German name is Es which is also how you pronounce the letter s.
So, the tritone is E♭ B B for German SBB, C F F for French CFF, and F F E♭for Italian FFS.
There is a version replacing the last note with its cord, which is used for announcing major stops.