He incorporated the previous work of scientists like Michael Faraday (fields and lines of force), André-Marie Ampère (electrodynamics), and Carl Friedrich Gauss (electrostatics).
A coherer was an early radio wave detector consisting of a glass tube filled with metal filings. Its resistance decreased when exposed to radio waves. It was invented by Édouard Branly, and later improved by Oliver Lodge.
He used a spark-gap transmitter (a dipole antenna with a spark gap) to generate waves and a simple loop of wire with a small gap (a resonator) to detect them.