Interetsing Unit for UPY

I noticed this picture. It is of UPY #2706. The locomotive designation is a 3GS21B. Now, after a little research, I cannot seem to kind a lot of information on this type of unit. I know BNSF has a few too. They remind me of a stretched switcher!

Anyone knowmore?

It says pretty much everything about it, in about the middle of the long hood!!!

"Ultra Low Emissions Diesel Genset Switcher"

It has 3 engine/generator sets (aka Gensets) which in total provide about 2100 horsepower. Each engine produces about 700HP, and depending on the power required determines how many engines of the three are on - it saves fuel compared to say a GP38, with one engine and putting out 2000HP, that is always on, no matter how many cars its pulling or sitting at idle. the genset can shut the other engines off and only be running on the one while at idle or while moving itself around lite, or pulling one or two cars.

Ok, thanks.

there's an ad for them on the back of some recent TRAINS magazines. that's all i can tell you.

Isn't that all Cummins power in there?
Yeah, a "TRAINS" magazine has info on the Genset switchers.
Each engine seems to have its own alternator. With both the D77 and D78 traction motors available on either of the two Gensets, how can you tell as to which type is used?