It looks like what you have is a sound and motion DCC decoder. Like many decoders - if not all made in recent years - it can work on either DC or DCC. You'll need to do a "hardwire" installation, two wires from the decoder goes to the track pickups, and two wires go to the motor (assuming the DC battery powers the track, and isn't onboard the engine?) The motor must be isolated from the frame, so it's only getting power thru the decoder. You'll also need to attach a speaker, unless one came already attached.
I suppose you could connect it up to the track power only, and use it as a "sound only" decoder, but you could have gotten a sound-only decoder for quite a bit less than the decoder you have. But it would work OK as sound only. You could also attach a larger speaker and run it as an "under the table" sound system, not attached to the engine per se.
Anyway, with a diesel sound, yes the diesel RPM sounds should rev up as you apply power to the model. You can adjust the rate using the CVs (control values) of the decoder.
How do on-board sound modules work electricly? My question is mainly in regards to the Prime mover soud. Does the sound chage due to the voltage change to the motor or something else?
I want to hook up a MRC on-board sound module with transmitter into a LEGO battery powered DC locomotive. I am only concerned about getting the horn, bell and prime mover sounds to work (the module also allows for various light controls which Im not conecernd with yet). Im just not quite sure how it needs to be wired to the motor and am afraid to try it so as not to risk damaging the module as Walthers sells them for $66 and says they are discontinued after they sell out. Any help would be greatly appreciated.
Here is the MRC isound module nfo:
http://www.modelrectifier.com/resources/trainsound/0001000-1001ins.pdf
Thanks,
Sal
WFB, WI