I've had many sets of air horns on my vehicles from double, triple and even had up to 8 trumpets covering two sets at one stage. Had Mexican hat dance, dixie, alternating triple LOVE EM LOL.
What Gonz has sounds like a standard tri-tone airhorn. Single line from air pump split to each trumpet.
The picture earlier looks like the alternating triples, normal operation is all at once, flick a switch and it will alternate high, middle, low, middle, high, middle, low, middle etc in rapid succession.
Next step for me is a twin trumpet from a truck or train, already have the air tank and compressor mounted for tyre inflation.
