What do you mean "descramble"? If you have a digital cable box, you have to input an analog signal from that box into your tuner. Otherwise, if you've just got normal cable service that doesn't require the digital channel changer, plug the coax cable straight into your TV card, and, assuming you've got the supporting software, you can change the channels from your computer and do time-phase recording. The only cards that do digital are pulling the signal "over the air" (OTA).