The prototype of the DT-6-6-2000 was commissioned by the Elgin, Joliet and Eastern Railway, which ultimately used 27 of the 45 locomotives of this type. These were transfer switchers for handing over freight trains between marshalling yards. A central cab lay between two engines. Two naturally aspirated eight-cylinders were used in the prototype, which were replaced in series production by six-cylinders with turbochargers. Many locomotives were later modernized with new engines from Baldwin or EMD, each with 1,200 hp. 