So I have the CDJ setup and here's a way to split the fader start signal. You have 4 CDJ 900/2000/2000nexus and either a DJM 900nexus or a DJM 2000. Both mixers work, and all 3 CDJs should work, but this is what I use for a DJM 900nexus and 4 CDJ 2000. Make sure they are all connected by PRO DJ LINK...