Description: 1.ABY box (also known as AB circuit selector). Signal is introduced from the “IN” socket. Foot-controlled switch directs the signal to line A or line B. The active line is indicated by indicator light. The other line is silenced (Note: it is silenced not open. Other AB box products open up the other line, which can cause signal interference and other problems). This AB box product is capable of switching between A and B lines at will or simultaneously activates both lines. For best results, please use low resistance equipment for the real time signal inputting. 2.This product is powered by any 9V source just for the indicator light. In other words, the function of this product does not require electric power because the signal lines and indicator lights are totally separated. Consequently, the quality of sound can be perfectly preserved and no noise is generated during signal transfer