 Its microcomputer network control system allows eight of these locomotives to work together in a multi-unit consist and also to work consisted to diesel-electric locomotives.The only externally visible differences between the Classes 20E and 21E are on the end sills, buffer beams, cowcatchers and the left side of the cab roof.The locomotive body is a welded monocoque design, constructed of steel plates and profiled members, which has a compressive strength of and a tensile strength of .