Resonant inductive coupling ("electrodynamic coupling", "strongly coupled magnetic resonance") is a form of inductive coupling in which power is transferred by magnetic fields "(B, green)" between two resonant circuits (tuned circuits), one in the transmitter and one in the receiver "(see diagram, right)". Each resonant circuit consists of a coil of wire connected to a capacitor, or a self-resonant coil or other resonator with internal capacitance. The two are tuned to resonate at the same resonant frequency. The resonance between the coils can greatly increase coupling and power transfer, analogously to the way a vibrating tuning fork can induce sympathetic vibration in a distant fork tuned to the same pitch.