Complex sentence: In 1893 he modified d'Arsonval's electrotherapy equipment by the addition of a wire coil resonator to produce higher potentials, inventing the Oudin coil, which was used in electrotherapy through the 1920s.
Split into simpler sentences: In 1893 he modified d'Arsonval's electrotherapy equipment by the addition of a wire coil resonator to produce higher potentials, inventing the Oudin coil. The Oudin coil was used in electrotherapy through the 1920s.