Introductory Direct-current generators Synchronous converters Mercury rectiflers Storage batteries Three-wire system Feeder panels Direct-current motors Direct-current circuit breakers Direct current stations Typical electric power stations Low-tensio alternating current High tension switching arrangements and methods of connection Circuit-interrupting devices Oil switches Relays Potential regulators constant-current systems Starting compensators Lightning arresters High-tension switchboards and wiring diagrams Cells and compartments Wall outlets Central stations Typical central stations