original_query: What were the reasons for reintroducing the two-wire or 'metallic circuit' system in the late nineteenth century? What is the most relevant chunk to answer the query?
query: What were the reasons for reintroducing the two-wire or 'metallic circuit' system in the late nineteenth century?
answer: The two-wire system was reintroduced in the late 19th century because currents in the earth induced by power systems, electric railways, other telephone and telegraph circuits, and natural sources like lightning caused unacceptable interference to audio signals.