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Modems are the heart of today's Internet world. With it we can connect to another world out there and surf the web at our leisure. The modem is installed (or replaced), the communication software is loaded, the telephone line is connected—and nothing happens. This is an all too-common theme for today’s technicians and computer users. Although the actual failure rate among ordinary modems is quite small, it turns out that modems (and serial ports, as you will see later in the book) are some of the most difficult and time-consuming devices to setup and configure. As a consequence, proper setup initially can simplify troubleshooting significantly. If a modem fails to work properly, there are a number of conditions to explore:

My PC (or communication software) refuses to recognize the modem?
First, verify that the modem is turned on (external modems only). For internal modems, see that the modem is installed correctly and completely in its expansion slot. Check your CMOS settings and verify that the COM port for your external modem is even enabled. There might be a COM port (IRQ) conflict in the system. Check the configuration of your internal modem (try the Windows 95 Device manager) and verify that there are no hardware conflicts. If you have trouble running the modem in “terminal mode” (the modem doesn’t respond to AT commands), be sure that you’re entering everything in either upper-case (AT) or lower-case (at) format—mixing cases can sometimes confuse a modem.

My modem is connected and turned on, but the modem is not responding?
The communication software’s configuration must match the port settings of the modem. Check to be sure that any modem parameters are entered and saved properly. Establish a direct connection with the modem and enter the “ATZ” command. This will reset the modem. The modem should respond “OK” or “0” (the numerical equivalent of OK). If that doesn’t work, change to COM2 and try again, then COM3 and COM4. If none of the combinations work, check the DIP switches or jumpers on the modem for the correct configuration.

My modem is configured as COM4 (IRQ3) under Windows 9x, but the modem refuses to work?
There might be a hardware acceleration issue. Go into the Windows 9x Control panel, double-click the System icon, select Performance, then click Graphics. Set Hardware acceleration to “None” and try the modem again. Some advanced modem manufacturers have found an addressing conflict with certain graphic-accelerator cards. If you configure your Windows 9x graphic driver to basic VGA, and find that the modem now works at that setting, then the problem is probably an addressing conflict with your graphics card. You might want to try using one of the more commonly used COM port and IRQ settings, such as:

My modem makes audible “clicking” noises when hooked to the phone line?
A short is probably in the phone line. The “clicking” is the noise of the modem trying to pick up when it sees the short and hang up when the short clears. Try replacing the line cord going from the modem to the telephone wall jack; line cords don’t last very long under constant use and abuse. If problems continue, try using a different telephone line—the physical wiring might be defective between the wall jack and telephone pole. Contact your local telephone company if you suspect this to be the case. Next, try establishing a direct connection to the modem and enter an “AT&F” command, which will restore the modem’s factory-default settings. If that clears the problem, the modem’s initialized state might not be fully compatible with the current telephone-line characteristics. Check each modem setting carefully and adjust parameters to try and settle its operation down. If factory-default settings do not help and the telephone line seems reliable, the problem might be in the modem’s telephone interface circuit—try replacing the modem.

My modem starts dialing before it draws dialtone?
As a result, one or more of the numbers are lost during dialing, making it difficult to establish a connection. Chances are that the modem is working just fine, but the modem does not wait long enough for dial tone to be present once it goes off hook. The solution is to increase the time delay before the modem starts dialing. This can be done by changing the value in the modems wait state before it begins dialing

Why can't I receive any calls while my modem is in use?
You will need to go into your modems configuration section and disable the call waiting feature on your modem to disconnect whenever your phone line receives an incoming call. Usually this will be a box with *70 next to it.

During installation, a modem setup program cannot find the internal modem?
In virtually all cases, you have a hardware conflict between the modem and another device in the system. Check the hardware installation first. For internal modems, be sure that the IRQ and I/O address are set correctly, and see that no other devices are using the same IRQ or I/O space as your modem. Under Windows 9x, the Device manager can usually display any conflicting devices with yellow icons (exclamation marks). Next, be sure that the modem is inserted properly into its bus slot. If any of the card’s gold “fingers” appear corroded or soiled, clean the fingers gently with a pencil eraser. Try the modem in another bus slot. Finally, check the modem switches. Most external modems use a series of DIP switches to configure its various features. Refer to the modem’s documentation and see that any modem switches are set properly.

After installing modem driver software, Windows locks up or crashes?
This is almost always the result of a defective or outdated modem driver. Check the software installation. Be sure that the modem driver software you have installed is the proper version for the particular modem, and your version of Windows. You can usually check the driver version on the modem’s manufacturer’s Web site. If you do find that the modem driver is incorrect, run any “uninstall” utility that accompanied the software to remove the driver cleanly—otherwise, you’ll have to remove the modem driver references from SYSTEM.INI manually. Under Windows 9x, you can often Remove a device from the Device manager, then allow Windows to redetect the modem during the next boot (and reinstall the new drivers at that point).

How can I make it so that whenever I get online I can keep my connection from being interrupted by an incoming call?
You will need to go into your modems configuration section and place a check in the disable call waiting. Usually it will be a box with *70 next to it, check this box and your call waiting should be disabled

Windows 95 insists on assigning my modem to COM5?
You will need to reconfigure the modem’s port assignment through the Control panel. First, you’ll need to remove any unused modem entries. Software that has been loaded for previous modems might interfere with the current modem’s software. Remove unused modem hardware references through the Device manager:

  1. Select My computer, double-click on Control panel, then choose Modems.
  2. Highlight any modems that are no longer in the system, then press the Remove button.
  3. If multiple entries are for the same modem, remove all entries for the modem, restart the system, then reinstall the software.

Next, verify that the modem is on COM5. Check to see that the modem is identified and checks properly before continuing:

  1. Select My computer, double-click on Control panel, then choose Modems.
  2. Select the Diagnostics tab.
  3. Highlight COM5 and press the More info . . . button.
  4. Verify that the modem responds to the “ATI3” command with its proper ID information.
  5. Click OK.

Now find an unused COM port. Check the Diagnostics screen and examine the COM ports in use—any ports not in use are available. Next, use REGEDIT.EXE to edit the Windows 9x Registry. You can change the COM port assignment by adjusting the Registry:

  1. Click on the Start button, then select Run.
  2. Type “REGEDIT” and click OK.
  3. Select the Edit/Find option, then type “COM5.”
  4. Click Find next—this should highlight Portname under a Registry key.
  5. Double-click on Portname.
  6. Enter the new COM port, such as “COM2.”
  7. Click OK, then close REGEDIT.
  8. Shut down and restart Windows 9x.

Before attempting to edit a Windows 9x Registry file, be sure to have a complete backup of the registry files SYSTEM.DAT and USER.DAT.

Finally, check the updated configuration and verify that modem now works on new COM port:

  1. Select My computer, double-click on Control panel, then choose Modems.
  2. Select the Diagnostics tab.
  3. Select the new COM port that you selected for the modem.
  4. Press the More info . . . button.
  5. Verify that the modem responds to the “ATI3” command with its proper ID information.
  6. Click OK.

When selecting a modem in my communication software, my particular modem is not listed?
You will need to obtain the proper driver supplements from the modem manufacturer (or software maker). Try running the modem as a Hayes-compatible—virtually all modems will function as generic Hayes-compatible modems.

It seems to take my modem an unusually long time to hang up?
The carrier delay time is probably set too long. Check the carrier delay time. Modems can be set to wait (often as long as 25 seconds) after a carrier is lost to see whether it comes back—if you frequently encounter poor signal quality, this can be quite convenient. After a legitimate hang-up, however, the modem might continue to wait. In this case, you might want to set the value of the register to a low number—10 or less.

When auto-detect tries to add a new modem at COM2, Windows 9x locks up?
Open the Control panel (System settings) and deselect COM2. This can be accomplished by selecting COM2 under System settings, then choosing Properties. A red “X” in a box should be toward the bottom of the Properties screen. Click once on the red “X” and it should clear. This disables the COM port in Windows 9x. Click OK, then restart the machine. When Windows 9x restarts, it should now find the COM port. This technique applies to all available COM ports.


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