"DPU"....(dee pee yew)
"Distributed Power Unit" - a radio controlled slave diesel unit (or multiples of) usually cut in the rear of long coal trains. They are controlled from the head end. They are different from the old remote control helper set ups in that the remote unit can be be operated independently of the head end if desired. In other words, it can either work in tandem with the head end or push less, more or even go into dynamic brake while the head end keeps pulling. Also when an automatic brake application is made, the DPU's will assist the reduction and set up too. Likewise, when the brakes are released, the DPU will also assist in recharging - magic stuff!
Just about every loaded coal train through Wichita Falls, TX (there are a lot of 'em) has 2 new Pumpkins on the head end with another Pumpkin cut in on the rear as a DPU. Usually the empty trains have all thre units on the head end.