For sale to organize equipment. This is a 4-channel (3 stereo + 1 mono) mixer. It's ideal for mixing audio signals and synthesizers, etc., and sending them to a sound card or recorder. Each channel is equipped with level control. In addition, there is a headphone/line output (shared). The output is mixed and output in mono. Only the main unit shown in the photos is included. Another unit is also listed separately. No returns or exchanges.