I have not hooked up my VHX cluster yet, but reading my instructions it says you just use the cat5 cable that comes with the clock and plug that cable into the side of the vhx control box at the display area of the box. There appears to be 3 jacks to use. There is a sheet labeled operating manual for clock/auxiliary displays for vhx systems, that comes with your cluster. (Or should) I might check into getting a second clock but man is this stuff spendy.