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| Troubleshooting Modems | Operation and
Connection Problems ]
I am able to establish a connection to a remote host, but I am frequently getting
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
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
- 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
- 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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