Starting at the front end, one immediately notices the distinctive rounded "bulldog" nose and cab section that was a classic EMD trademark for more than four decades. Introduced in 1939 on the EMD FT freight diesel, the "bulldog" nose was adapted to the E7 unit in 1945 when EMD resumed production of passenger diesels following World War II. This replaced the more slanted nose found on all prewar EMD passenger units. Immediately behind the cab is the engine room which contains two EMD model 567A 1000 horsepower, 12-cylinder diesel engines with an operational range of between 275 and 800 rpm. Located just forward of and just behind the center carbody door, each engine powers several important auxiliary components, the most prominent of which is an EMD model D4D main generator mechanically coupled directly to each engine. Each of the main generators provides 600 volts DC electrical power needed to operate two traction motors riding on each set of trucks. Each of the two main generators also drives an auxiliary generator which provides 74 volts of power for such items as the headlight, the cab gauges, and the main controller located in the cab. Each auxiliary generator, in turn, is coupled mechanically to a traction motor blower that provides cooling ventilation for the truck-mounted traction motors. In addition to powering the two generators, each engine drives (through a system of belts) four 26-inch-diameter radiator cooling fans located directly above each engine. The fans operate at the same speed as the engine in order to provide maximum cooling at the highest engine speeds. Adjacent to each auxiliary generator along the outer carbody wall is an electrical cabinet that contains numerous relays, switches, and other electrical gear needed to operate the locomotive. At the extreme rear of the unit is an oil-fired steam generator that provided heat for the passenger cars in cold weather. In most E7's, including all PRR units, this was originally a Vapor Corporation model 4530 generator capable of providing 3000 pounds of steam per hour. The underfloor components of each unit include a pair of three-axle truck assemblies especially designed for high-speed passenger service. Riding on the two end axles of each truck is an EMD model D7 electric traction motor, four in all. As in most electric locomotives, these motors convert electrical energy into mechanical force through a series of gears on both the motor and the axle. The center axle on each six-wheel truck is merely an idler used primarily to distribute the weight, thus providing a smoother ride at speeds above 65 mph. Between each of the two trucks is a 1200-gallon water tank for the steam generator and an identical 1200-gallon fuel tank. Every one of the 5901's sister units - 509 in all - have been scrapped. Among last survivors of their kind at the Museum, No. 5901 is assured the permanent place of honor she richly deserves among the locomotives that made railroad history in Pennsylvania.