How can I connect my surveillance camera to my cable which feeds the televisions in the house? I have tried to connect it into the cable line using a modulator. This modulator tunes to channels that are not broadcasting cable channels. But the result is a poor picture unless the cable TV line is disconnected. It appears that the signal from the cable TV is still blocking everything else on the line. Do I need some kind of special splitter, filter, etc. TIA for any help you can give.