Donner ABY box line selector switcher This is an ABY selector. Power is only used for the light; the switcher is passive. If you don't need the light, you can use it without power. * Normally, you connect a guitar to the AB box and then to two amplifiers, but you can also connect two guitars and play them through one amplifier. In that case, if you set the selector to Y and play both guitars simultaneously, the output of one will decrease. This is not a malfunction; it's the specification of a passive device. Please be aware of this. With original box.