The RB-PLI6 is a passive line isolation unit used to isolate audio signals from ground loops between areas, which can be caused by equipment powered from different mains supplies or phases on the same supply. The input and output are connected together via a transformer, and the unit has internal jumpers allowing inputs and/or outputs to be balanced with respect to ground. The unit requires no mains power to operate.

This unit is useful when audio needs to be transmitted over a relatively long cable length. By isolating the signal using transformers, ground loop currents that may be present in non-isolated signals are completely eliminated.