I don’t know why, but Soundtraxx is very elusive with this information. I bought a TSU-750 #827011 for an ALCO 539 non-turbo and it’s not listed on the card. I even went to Soundtraxx website and it is not easy to find this information for any of the decoders. You may need to just call them.
On a side note, I have an Athearn Genesis SD70ACe with a GN-1000 and the manual shows the settings for CV 115 (horn) are:
I have an older version of JMRI. For a AT-1000 710, it suggests that the K3L should be a value of 6 in CV115. For the TSU-750 Alco 244, it suggests that the value in CV115 should be 8.
Unfortunately the manuals are useless when it comes to answering the OP’s question. The manual tells you that for different values in CV115 you can get alternate horns 1, 2, 3, and so forth, but they don’t tell you what horns 1, 2, 3, and so forth are.
They are? I picked up a Loksound Select Alco 244, needed to set the horn to an M3RT1, and the little sheet included listed which values in the prime mover/horn select CV set which horn. No guessing.
MRC is the real bad one. They have the CV to set multiple horns but even their tech support has no idea which horn is which value of the CV. “We don;t keep records of that” is what they told me.
Then I recind my comment. I buy my Loksound decoders in bulk and they just come ten wrapped in bubble wrap. The few singles that I’ve gotten in the box were blank decoders and come with no documentation. The download section on the site doesn’t list the horns and their numbers. The problem is that with each new file, they are continually updating the horn selection and aren’t revising the older files for consistency.