The A.B Y unit is an entirely passive router therefore it is completely transparent. It allows routing a signal to amp A or amp B, or both. 2 bright LEDs, powered with a 9V battery or a power supply (not included), indicate which output is selected. In Y mode, a blue LED turns on while the A/B selection remains visible so you know which channel you're going back to when leaving the Y mode. With every Huge Audio router, the power is drawn only when a cable is connected to the input jack plug. Also, if no cable is connected there, the sound is electronically muted on all the amps. This means that absolutely no sound comes out of the unit then, even at maximum volume! Made in Germany.