I have some of the last MTH HO locomotives with PS3. I'll look this evening, but I don't think they have a DCS/DCC switch and the manual doesn't mention the switch. They mate fine with Kadee couplers. They do ride a little low compared to the position of Walther's couplers but I run these consists at 70+ smph and they've never come apart yet.
I have run into other issues though: 1) the sound messes up at 73 spmh (the sound slot for this speed is garble and it messes up the sound decoder), 2) some of the last locomotives do not have the engine throttle sounds at all so the engine always sounds the same regardless of speed, 3) be sure to turn off the click-clack auto sound (it doesn't mix with any of the other sounds so you can't use the horn, bell, etc...).
I've also gotten a lot of oil on the tracks which I believe have come from one of the HO locomotives. I suspect the so called sealed gear box is not so sealed. I always have to clean the tracks really good before each run.
Anthony
