The A/B 5.1 surround switcher can be used to compare alternate mixes (ie DAW mix output to a DVD output) or as a surround alternate speaker selector. There are 3 groups of 6 input/outputs on 1/4\" TRS connectors. These can be connected as two inputs to one output (to compare mixes) or one input to two outputs (for alternate speakers). The A/B5.1 has balanced inputs and outputs and is passive. Switching is done with relays there are no electronics in the audio signal path.