E-units standardized the two engine configuration for passenger locomotives to maximize power and, while the less-reliable Winton Diesel prime movers were in use, faced a less severe loss of power should one of the engines become disabled. While E-units were used singly for shorter trains, longer trains needed multiple locomotive units; many railroads used triple units. E-units could be purchased with or without cabs; units with a cab are called A units or lead units, while cabless units are called B units or booster units. B units did contain hostler controls, but they could not be so controlled on the main line. The locomotive units were linked together with cables which enabled the crew in the lead unit to control the trailing units. Railroads tended to buy either ABA sets (two cab-equipped units facing in opposite directions with a booster in between) or ABB sets (a single cab with a pair of boosters). The former did not need to be turned to pull in either direction, but B units were less expensive than A units and gave a smoother line to the train.