The PCDI is a passive direct box that converts unbalanced stereo line signals such as CD players, MDs, computer sound cards, tape decks and other unbalanced stereo line signals into low-impedance balance signals. The connector has a 3.5mm mini TRS stereo jack or RCA phono jack, through, RCA phono jack, and an XLR male connector on the output. Stereo mono switch is a switch for stereo operations or stereo input into a mono and output each one. It also has a ground lift switch and a 20dB PAD switch.