It was the period of iron wire, imperfect transmitters, grounded circuits, boy operators, peg switchboards, local batteries, and overhead lines.
(It; was; the period of iron wire) (imperfect transmitters, grounded circuits, boy operators; peg; switchboards, local batteries, and overhead lines)
It imperfect transmitters, grounded circuits, boy operators
was peg
the period of iron wire
switchboards, local batteries, and overhead lines