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[ The PC Guide | Troubleshooting and Repair Guide | The Troubleshooting Expert | Troubleshooting Specific Components | Troubleshooting Modems | Operation and Connection Problems ]

I am able to establish a connection to a remote host, but I am frequently getting disconnected

Explanation: Your modem is able to dial out and connect to the remote computer you are trying to use. However, the connection is either unstable, or works for a while but frequently disconnects you without warning.

Diagnosis: There are a wide variety of different causes for disconnections. The most frequent one is actual interruption of the phone line upon which the connection is being made. Other causes include software or hardware conflicts or actual hardware problems.

Recommendation: Try to observe the situations under which disconnections occur, to see if there is any discernible pattern. Bear in mind that disconnections may not always be consistent, because modems have the ability to recover from some interruptions, especially short ones. Then consider the following specific causes of disconnections:

  • Make sure you do not pick up a phone extension that is plugged into the same line that you are using. Picking up a handset on the same line the modem is using, or trying to access the line with another modem at the same time that one is using it, may cause the call to be dropped. Often, however, the modem can recover from the interruption (although not always).
  • You may be experiencing interference from a call coming through on call waiting. As you probably know, when a call waiting call comes through, the phone conversation is interrupted and a short beep is heard. Modems do not like having their conversations interrupted. :^) In most cases most modems (especially newer ones) will recover from this but some may not. See here for more on what to do about this if it is a continuing problem.
  • Line noise problems can definitely cause disconnections. Try using the phone you are dialing out on with a voice handset. Listen for a hum or ring on the line by dialing a number with a voice phone and listening closely. You should actually complete a call, not just dial a number on the phone. If you hear an audible hum or ring then your phone line quality is suspect and very well may be the source of your difficulties.
  • If you have two phone lines then you may be experiencing cross-talk interference from one line to another, although this is not that common. If your modem is on your second phone line, see if you can pin the disconnects down to when the first line is used or rings. If so, there may be a fault in the way the phone lines are wired into the house, which the phone company will have to address.
  • There may be a problem with software interfering with the operation of the modem. For example, sometimes screen savers may kick in during a download and interrupt the normal data flow to the modem. Memory-resident programs might cause problems as well, so disable as many of them as possible.
  • There could be an intermittent resource conflict with the modem, such as that caused when you have the modem on an IRQ line that is shared with a device on another COM port. If you see behavior like the modem cutting out when the mouse is moved, this is a good indicator.
  • Make sure that the modem and its software are both correctly set up and configured, as incorrect configuration may lead to improper behavior.
  • Ensure that the modem is not overheating. If the components on the modem overheat then this can cause spurious results. If the modem is an internal one and you suspect heating problems within the case, look here.
  • If power management features are being used, they need to be set very carefully to ensure that they don't kick in during a download and disrupt the modem. I usually recommend simply disabling them (especially when troubleshooting a problem of this sort).
  • If you have only been trying the connection with one remote host, try another one. The problem could very easily be with the host at the other end of the connection. Problems there can range from overloading to incorrectly-configured server software.
  • Electrical storms and other severe weather can interfere with modem operation by causing intermittent line noise. Don't be surprised if you have disconnections if using a modem during one of these storms. Note that a surge suppressor with modem protection will not help with this, as it only provides protection against a strong surge that could damage the modem. It won't clear noise from the line.

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