You can get this information out of your modem's manual. Most modem manufacturers offer an upgrade that will allow you to upgrade your v. FC modem to a v. In the past, problems of this sort have appeared with Supra firmware upgrades to turn their 28.8 modems into 33.6 modems, and on early X2 modem models. If you are experiencing disconnects and have either a new modem or recently updated your modem's firmware, you might want to check with your modem manufacturer to see if a fix has been released.
Inactivity can also cause disconnections.
Most Internet dialer software will automatically drop the network connection after a few minutes of inactivity. If you are connected for over 5 hours and our system is experiencing peak usage which is resulting in busy signals, you may be disconnected in order to be fair to our other customers. Simply dial back in if you need to continue to use the system. Some modems are better than others at holding connections. If all of the above measures have failed, you may want to disconnect all of your other phone and fax equipment from the line for testing to see if possibly one of your other telecommunication devices is knocking you offline.