If you can get the cable modem to lock off of one of the lines after the splitter, then both of them will work. Look to see if the splitter says how much loss is there is for each leg. Go with the one ...

I have a filter plugged into my wall phone line. I have a phone line plugged into the filter which goes to my modem for internet service. My phone service is Vonage, a VoIP service and the phone I ...