Kusan-Auburn F-7 Diesel Locomotives

The F-7 engines had a hefty 7-pole AC/DC Pittman motor, which was rated for operation up to 25 volts, and rubber tires were installed on all four drive wheels, thus making these engines very strong pullers. Kusan-Auburn also offered an optional "DUO-TRAC" system, for a slight additional charge, which enabled their locomotives and rolling stock to operate on either two-rail DC or three-rail AC track. For DUO-TRAC, the wheels on either side of an engine or train car were insulated from each other. A slide switch underneath the bottom of a DUO-TRAC engine had two settings: "2 RAIL" and "3 RAIL" and could be changed by the operator, depending on what type of track system they were using. The Texas Special A unit pictured below did not come with the DUO-TRAC upgrade, but the Southern AA units were equipped with it.