The problem is that your questrion is too general. As I said before, most 4 wire systems use the 4th wire for a clocking signal and these will NOT work with our controllers. This set according to Ray is isolating the signal ground from the power ground but that is uncommon. Since it appears that there are multiple types of 4 wire sets, what you need to do is get the model number of or a link to the string that you are looking at and ask if anyone has tried that specific set.