You can usually make it work if you slow it down. TIVO/DIrectv, etc... can't slow down. BUT; if you slow your modem down to 14.4 or 9600 it could work. My fax machine works flawlessly and I had to set it for 9600 baud. I've used dialup modems on voip also and many times it works fine if you slow it down. Remember to slow down BOTH DTE and DCE. Slow the modem physically down, then go into your dialup settings (Default is 115000) and slow it down also to what you set the modem for. Later... Mike....