Modem Disconnections

What causes modem disconnects ? ............. Generally, there will always be an occasional disconnect. After all, we are dealing with phone lines being pushed to their limits with V.32, V.34 & 56kbps 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:
Disconnection's 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 USR modems and other modems, add S25=200 to your Modem String. 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 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 4: 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 5: 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 6: Modem won't dial. Try a regular phone on the modem line and listen for dial tone. If there is no dial tone the problem is the phone line and not the modem. Try X1 to disable dial tone detection. Try pulse dialing ATDP instead of ATDT. Try dialing manually with a phone and then use ATX1O

Reason & Solution 7: Modem dials but won't connect. Try adding commas after the phone number to increase the time the originating modem waits for carrier, or increase the value of S7. (e.g. AT S7=100 DT 1234567 or ATDT 1234567,,,,) Try X1 for simple result codes esp. if VOICE result appears after modem tone is heard. Try configuring for a slower link rate (set a lower port speed in your software or modem).

Reason & Solution 8: Modem hangs up for no reason during a connection. Disconnect all other phones and answering machines on the same line to see if any of them are interfering. Call your phone company if you can hear static on your lines. It is possible your modem may have a bug in its ROM, get in contact with your modem manufacturer to check on the version of your ROM or for other oblems unique to your modem. Also the modem speed may be set to, to high a speed. Essentially any modem between the speeds of 28.8kpbs and 56kpbs should be set to the speed of 57600, not 115200. The modem speeds need to be changed within the dial up networking connectoid, as well as within the modem properties within the control panel. it would also be worth while to check whether the TCP/IP protocol has been installed within network, within the control panel. If this protocol has not been installed.

Reason & Solution 9: Call waiting disconnects data calls. Disable call waiting with *70 (or *71 in some areas) before the phone number. AT DT *70, 111-2222 or AT DP 1170+ >111-2222 (Pulse) (Note this feature is not always available, call your local telephone company to be sure.) Try increasing the value of S10.

Reason & Solution 10: Why is my 28.8 or 33.6 Modem Connecting at 57,600 or 115,200? First of all, your modem is NOT communicating with the remote modem at 115,200 BPS! What >you are seeing is the DTE rate (the speed your PC is talking to your modem)>instead of the DCE rate (the speed your modem is talking to the remote modem). What you want to see is the DCE speed -- the communications speed that the two modems negotiate with each other when they CONNECT. There are two reasons you may be seeing the DTE speed in your modems CONNECT message. The most common one is that your modem is set to display the DTE rather than the DCE speed. Some modems display DTE speed by default -- if you don't change the default, you will not be seeing the actual CONNECT speed of the two modems. So the first thing to do is check your modem's manual and make sure your modem is set to display the DCE speed in its "CONNECT" message. The other thing that causes display of DTE speed is using Win95 without having the proper ".inf" file for your modem. The .inf file lists all the CONNECT messages your modem can produce -- if you have an outdated one that does not contain the proper messages for your updated modem, Win95 can't figure out what is going on with the DCE speed so it displays the DTE speed instead. The solution to this problem is to visit your modem manufacturer's site and download the most current .inf file for your modem, and put it in the Win95 "inf" subdirectory, and make Win95 "reinstall" your modem.

HSP Modems These modems work by using a specified percentage of the CPU, by utilising a portion of the unused instruction cycles of the CPU, to process data from >the modem, and because of this it is likely that you will need a driver for the modem that is specific to the manufacturer of your CPU, for it to work properly, for instance Intel, AMD, Cyrix. If you have applications running in the background, when using the modem, you will have less CPU time available to process information to and from your modem. This can have an influence on the modems performance and it's ability to maintain a connection. To actually use this modem there is a minimum speed of processor that can be used. For Intel CPUs the restriction is a minimum of a P90, and the restriction varies again for AMD and Cyrix. They will not work on low-end speed CPUs such as the 486 or less. Note: The USR equivalent for the "HSP" based modem is the Winmodem. These types of modems can be affected by video cards that use S3 chips, and disconnection's may occur. If frequent disconnection's are occurring and you have a video card installed in your computer that uses the S3 chips, and you >are using more than 256 colours in Windows95/98, you could try making the following change in your system.ini file under the [display] section:- [display] BusThrottle=1 and then resave the system.ini file. In some cases where frequent modem disconnects occur and your video card >does not use the S3 chips, you can try reducing the hardware acceleration in Windows95/98 to maintain a steady connection.For further information of "HSP" based modems visit the PCTEL web site at www.pctel.com For information on USR's Winmodem visit the USR site at www.3com.com