Cow-calf

In North American railroading, a cow-calf (also cow and calf) locomotive is a set of switcher-type diesel locomotives. The set usually is a pair; some 3-unit sets (with two calves) were built, but this was rare. A cow is equipped with a driving cab; a calf is not. The two are coupled together (either with regular couplers or a semi-permanent drawbar) and are connected with MU cables and brake lines so that both locomotive units can be operated from a single cab.