In electronics, inductive coupling refers to the transfer of energy from one circuit component to another through a shared magnetic field. A change in current flow through one device induces current flow in the other device. The two devices may be physically contained in a single unit, as in the primary and secondary sides of a transformer, or may be separated as in the antennae on a transmitter and a receiver. Coupling may be intentional or unintentional. Unintentional coupling is called cross-talk, and is a form of interference. Inductive coupling favors low frequency energy sources. High frequency energy sources generally use capacitive coupling.