Rane Serato SL4
The SL4 gives you the freedom to take your entire digital music collection on the road with advanced Serato features that add extra creativity to your DJing. This intuitive digital vinyl system replicates the traditional DJing experience for "real feel" usability. The Rane SL4 USB interface connects up to four vinyl or CD turntables to your computer using a single USB cable with audio connections to line inputs on your DJ mixer of choice. It is the first standalone DJ interface with two USB ports for seamless DJ changeover and back-to-back performances.
More info about the Rane Serato SL4 can be found here.