Balun

A contraction of “balanced” and “unbalanced.” Originally popularized by radio engineers, it referred to the transformer used to connect a balanced or symmetrical load (such as a dipole antenna) to an unbalanced load (such as a coaxial-cable feed line). Today, it has been expanded to refer to any interface (usually a transformer) between balanced and unbalanced lines or circuitry. A balun may also provide impedance transformation, as 300-ohm balanced to 75-ohm unbalanced, or vice versa. Another popular use is in transitioning between balanced twisted pair and an unbalanced coaxial cable.