Editing Transformer (section)

===Other early transformer designs===
In 1889, Russian-born engineer [[Mikhail Dolivo-Dobrovolsky]] developed the first [[Three-phase electric power|three-phase]] transformer at the [[Allgemeine Elektricitäts-Gesellschaft]] ('General Electricity Company') in Germany.<ref>{{cite book|last=Neidhöfer|first= Gerhard|others=In collaboration with VDE "History of Electrical Engineering" Committee|location= Berlin | isbn= 978-3-8007-3115-2|url=http://d-nb.info/990964361|title=Michael von Dolivo-Dobrowolsky and Three-Phase: The Beginnings of Modern e Technology and Power Supply |language=de|year=2008|publisher=VDE-Verl.|edition=2nd}}</ref>

In 1891, [[Nikola Tesla]] invented the [[Tesla coil]], an air-cored, dual-tuned resonant transformer for producing very [[high voltage]]s at high frequency.<ref name="PBS">{{cite web|last=Uth|first=Robert|title=Tesla Coil|date=Dec 12, 2000|work=Tesla: Master of Lightning|publisher=PBS.org|url=https://www.pbs.org/tesla/ins/lab_tescoil.html|access-date=May 20, 2008}}</ref>

[[Audio frequency]] transformers ("[[repeating coil]]s") were used by early experimenters in the development of the [[telephone]].<ref>{{Cite web |title=telephone {{!}} History, Definition, Invention, Uses, & Facts {{!}} Britannica |url=https://www.britannica.com/technology/telephone |access-date=2022-07-17 |website=www.britannica.com |language=en}}</ref>