The A.B Loop unit is an entirely passive router therefore it is completely transparent. It is the combination of an A.B unit and a Loop unit in one single box. A bright LED, powered with a 9V battery or a power supply (not included), indicates when the loop is engaged. 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.