INPUT AND OUTPUT: The 4 channel mixer's inputs and outputs include four stereo RCA inputs and one stereo RCA output. OUTPUT indicates that it is used to connect the RCA jack to a mixer output or other output device; IN 1‑4 indicates that it controls the signal level from inputs 1‑4. APPLICABLE: Stereo four channel passive mixer for extended control of tuning, mixing instruments, CD players, tape decks, computers, mobile phones, tablets, etc. SUPERIOR PERFORMANCE: Mini mixer produces the highest sound quality at all output levels, boasting ultra low noise operational for outstanding sound performance. Distortion free and easy to set up. CONVENIENT TO USE: The modern design of the passive mixer looks great on any desktop, with large controls that are easy to use and small enough to avoid twine of wires, clothing etc. EASY TO USE: No batteries or other power source required. The stereo mini mixer can also be used as a 1 In 4 Out stereo splitter with clockwise volume adjustment.