when you get traktor, it will come with the time code CDs and time code vinyls. that cd sends the signals through the mixer, through the traktor box, into the pc and then reversed. therefore you dont need to plug the cd players into the pc. DVS systems are used because turntables are old technology, however DVS enables the turntables to be synced with the pc, through a simple box and a vinyl. i can answer more questions if u have any.