A DI unit, DI box, direct box, or simply DI (variously claimed to stand for direct input, direct injection, direct induction or direct interface), is a device typically used in recording studios to connect a high-impedance, line level, unbalanced output signal to a low-impedance microphone level balanced input, usually via XLR connector. DIs are frequently used to connect an electric guitar or electric bass to a mixing console's microphone input.