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If you are experiencing problems with your Dial-Up connection or modem, the following information may be useful in troubleshooting and solving the problem. First, a brief primer on modem Internet connections. The word "MODEM" is short for "Modulator / De-Modulator", which describes a modem's function. A modem takes the digital signal from your computer and converts it (modulates it) into sound waves for transmission over your phone line to our dial-up equipment, which then de-modulates the sound waves, converting them back into a digital signal for transmission out to the Internet. Data coming to your computer from the Internet is first modulated by our dial-up equipment and transmitted over the phone lines as sound waves until it reaches your modem, which then de-modulates the sound waves, converting them back into a digital signal for your computer to use in displaying a web page in your browser or downloading email to your email program. It is during the period where the signal traveling to or from your computer is on the phone lines in the form of sound waves that it is most susceptible to interference. Any noises, such as static, clicks, pops, etc., on your phone line, or in any of the connectors (wall jacks, splitters, phone cord) to your modem, can interfere with the signal or degrade its quality. The degraded signal arrives at the receiving end (either your modem or our dial-up equipment) with errors, which requires that the erroneous data packet be retransmitted. Sometimes this retransmission process must be accomplished over and over for the same data packet before it is received without errors. At best, these retransmissions slow down the effective speed of your connection. At worst, the two ends of the connection can get so far behind that they give up and drop the connection. These dropped connections show up in our dial-up equipment log as a "Lost Carrier" disconnect. Your phone company may service extreme
noise on the phone line if it interferes with telephone conversations.
Often, however, the interference may be mild enough that it does not interfere with telephone conversations but can still wreak havoc with a computer Internet connection. In these cases you may not receive satisfactory resolution of your line problems from the phone company, as they are not obligated to condition telephone lines to handle computer connections. Their only legal requirement is to provide for 4800 baud connectivity, which equates to 4.8 K, which would be a useless speed for Internet activities. Having said that, what follows is some information on things that you have control over, and can check out in an attempt to solve problems that you may have. Also, at the bottom of the page are some links to websites offering additional modem help resources. Q. Why does my modem abruptly disconnect sometimes? Generally, there will probably always be an occasional disconnect. After all, we are dealing with phone lines being pushed to their limits with V.34 and V.90 modems. Phone lines were designed for voice, not for data transmission. But if you're getting a lot more than the occasional disconnect, something is wrong and you should methodically follow the steps below. Reason & Solution #1: Disconnections may be caused by momentary drops of DTR (Data Terminal Ready). By default, most modems respond to a drop of DTR by hanging up. With US Robotics modems add S25=200 to your Modem String, with other modems add S10=50. This sets the duration, in hundredths of a second, that DTR must be dropped so that the modem doesn't interpret a random glitch as a DTR loss. Reason & Solution #2: A similar possibility to the one above is that your modem could not distinguish between a line hit, or other disturbances that momentarily break the connection, from a true disconnect by the remote modem. Add S10=100 to the Modem String to set the duration, in tenths of a second, that the modem waits after loss of carrier before hanging up. Reason & Solution #3: If you have call waiting and a call comes in while you are connected to I-Link, your modem might interpret the second signal as a disconnect by the remote modem. Ask your phone company how to temporarily disable call waiting. Also, keep in mind that I-Link has an idle timeout. If there is no modem activity on your end for 20 minutes, you will be disconnected. Reason & Solution #4: If you suspect line noise, try solutions #1 and #2 above. Also, listen in on the line for static, ask your phone company to test the line (although they usually only test for voice grade as opposed to data grade), and try reducing your baud rate (a.k.a. port speed). Also disconnect EVERYTHING from your phone lines, including a laser printer from the electrical outlet. Do not use devices that allow you to connect your phone line to an electrical outlet. Also, keep the phone line at least three inches away from electrical cords, extension cords, printer cables, etc. Inductance from electrical lines and radio transmitters wreaks havoc with phone lines. And avoid using phone splitters of any kind. Reason & Solution #5: One common cause of disconnects is modem incompatibility between your modem and the remote modem. No modem is completely compatible with every other modem. Be sure to check with the modem manufacturer periodically for firmware and driver upgrades. Do not assume that just because your modem is new that it contains the latest firmware and drivers. Reason & Solution #6: Check your phone cable for defects. Or better yet, just replace it with a brand new one. Also, if you have an external modem, make sure your modem cable connections are tight and the cable is also free of defects. Generally, the modem cable should be replaced every year or so, depending of course on frequency of use. Reason & Solution #7: If you're disconnected shortly after logging in, you may be attempting simultaneous logins on the same account. Make sure no one is logged-in to your account such as a family member at home. If this isn't the case, try to add a Modem String to make your connection stronger. Check your modem's instruction manual for specific information about settings.
Line Noise Troubleshooting Line noise can have many sources. Here are some things to try to diagnose or solve the problem: 1. Unplug answering machines, other phones from your phone lines and see if you still get the garbage characters when you dial up. Some devices can put a small drain on the phone line current and interfere with your modem transmission. 2. Unplug both ends of the phone cable (from the modem and the wall) and plug it back in. If your modem is external, do the same for the cable connecting the modem to your computer. 3. Wiggle the phone cable while you're dialed up and see if the garbage characters appear. If they do, you might need a new cable. They're pretty cheap, and you can find replacements at most discount department or electronics stores. 4. You can also clean off the gold contacts on the jacks and plugs with a contact enhancer such as Stabilant-22 (designed for stereo products.) Make sure the computer is unplugged when you do this. 5. When talking on the phone, listen carefully for line noise. If you hear static of any sort, your local telephone lines or the phone lines in your house may be at fault. Call your local telephone company and request investigation or repair. 6. If the source of the problem is the phone lines in your house, you may be billed for the service call. 7. Be sure you've got the right settings in your modem program (ProComm, Telix, Zterm, etc), like the proper baud rate for your modem, 8 data bits, no parity, 1 stop bit. 8. If all else fails, you can go to a lower baud rate, or buy one of the error-correcting modems available on the market now. Some can even handle people picking up the phone in the middle of a call. 9. You may want to purchase an inexpensive line noise suppressor from Radio Shack or a local electronics store. The adapter is called RJ31X Line Noise Suppressor, which costs $3-$4. In most situations it very affective in rectifying to random disconnects. 10: Also, home security system, flourecent lights w/ ballasts, stereo systems, and any kind of splitters, A/B selector switches are possible causes of line noise that may be an easy fix. Dial-Up Networking Errors 629, 640, 691 OR 734 These errors are discussed in Microsoft Knowledge Base Articles 310431 and 314455. These documents list several items that you can check out:
Any of the above items can be possible causes or contributing factors. You may want to try making single changes between connection attempts to avoid changing more than you need to. Modem support website links: |
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