Rane SL4 Serato Scratch Live Dual USB Interface two computers & four decks using your favorite mixer. The SL 4 connects four vinyl turntables or CD players to your computer and the mixer of your choice. Using special control vinyl, CDs or MIDI controllers, you can scratch and mix files from your Mac or Windows computer's CD or hard drive. This intuitive system replicates the traditional DJing experience for real feel usability. With unparalleled performance, stability and audio quality, you'll know why thousands of DJs worldwide choose Rane with Serato Scratch Live. The SL 4 is the first standalone DJ interface with two USB ports for seamless DJ changeover and back-to-back performances. Superior sound is delivered with high quality 96 kHz, 24-bit audio.