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.