invented the Tesla coil, an air-cored, dual-tuned resonant transformer for producing very high voltages at high frequency. Audio frequency transformers ("repeating coils") were used by early experimenters in the development of the telephone. See also High-voltage transformer fire barriers Inductive coupling Load profile Magnetization Parametric transformer Polyphase system Power inverter Rectiformer Voltage converter Notes References Bibliography External links General links: (Video) Power transformer inrush current (damping) (Video) Power transformer overexcitation (damping) Three-phase transformer circuits from All About Circuits Electric power conversion 19th-century inventions Hungarian inventions British inventions