The appearance of silicon rectifiers allowed the AC output of the alternator to be converted to DC for battery charging and control circuits. The introduction of solid state electronics also saw the old mechanical voltage regulators replaced. The 3-phase is also converted to DC by the rectifier which provides current for battery charging and control circuits. On a diesel locomotive, this supply would come from an on-board alternator driven by the diesel engine. Gaps A feature of electric railway operation is the gap or neutral section.
Gaps occur in third rail systems and neutral sections in overhead line systems.
See also Electric Traction Power Supplies . Neutral sections in the overhead line are also used for this purpose. Although they are always kept as short as possible, gaps will sometimes cause loss of current to the train. On trains provided with generators or alternators, the momentum in the machine would often be sufficient to maintain some generation over the gap and lighting often remained unaffected. The only difference noticeable to the passenger was the change in the sound of the generator as it lost power and then regained it a second or two later.