Assuming you're talking about a data connection over the phone line (like using a modem to connect to another modem, or to your ISP), you can't do that in VB, you'd have to use the sound card to decode it. You're talking about phase modulation, and there's nothing in VB that would allow you to determine phase change in an audio wave form. Depending on how you recorded it, the phase information might not even be recorded accurately enough to recover the data.