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Troubleshooting Modem Problems Under Windows NT 4.0

This article was previously published under Q161516
This article has been archived. It is offered "as is" and will no longer be updated.
This article describes procedures to help you diagnose and fix problemswhen you are unable to dial out using your modem in Windows NT 4.0 withDial-Up Networking (DUN).

Installing Your Modem

If your modem is not on the Windows NT 4.0 Hardware Compatibility List(HCL) or is not detected by Windows NT, use one of the followingprocedures to install it:
  • Obtain from the modem manufacturer an .inf file designed for Windows NT 4.0. Follow the manufacturer's instructions for installing the modem in Windows NT 4.0. Contact the modem manufacturer for assistance with this procedure.
  • If your modem has an .inf file for Windows 95, you may be able to use that file under Windows NT. When you are adding the modem through Control Panel, Modems, check the box labeled, "Don't detect my modem; I will select it from a list." Choose the "Have Disk" option and insert the disk containing the Windows 95 .inf file. Please be aware that not all Windows 95 .inf files will work correctly in Windows NT 4.0.
  • Install your modem as a standard modem using the following steps:
    1. In Control Panel, double-click Modems. The Install New Modem Wizardstarts automatically if you have not installed a modem before. Ifthe wizard does not start automatically, you have installed a modempreviously and you should click Add to start the wizard.
    2. Check the box labeled "Don't detect my modem; I will select it froma list," and then click Next.
    3. In the Manufacturers box, click Standard Modem Types. In theModels box, click a model that corresponds to the speed of yourmodem, and then follow the instructions in the Install New ModemWizard.

Verify Your COM Port(s)

Verify that Windows NT recognizes your COM port(s) by double-clicking thePorts icon in Control Panel to see if the COM port that the modem isconnected to is listed. If it is, Windows NT recognizes the COM port.

If the COM port is not recognized in the Control Panel Ports applet, thereis most likely a hardware problem or a configuration problem. Use thefollowing steps to troubleshoot the problem.

External Modems
  1. If the COM port is on the motherboard or is provided by a serialcard, make sure the port is not disabled in the BIOS (also calledthe CMOS) setup of the computer. Refer to the documentation for yourcomputer to obtain information about configuring options in the BIOSsetup.
  2. Make sure there are no other adapters or devices that are configuredfor the same Base I/O Address or IRQ as the COM port to which themodem is attached.
  3. Verify that the serial port is not defective. If the modem and anyother serial devices fail on the COM port but work on other COMports, and you have verified the two steps above, the serial portmay be defective.
  4. Verify the serial cable is not defective by using a new standardserial cable.
Internal Modems
  1. If the COM port is defined by an internal modem, make sure thejumpers on the modem are configured properly. Internal modems willalmost always have a jumper on the adapter that configures the modemas a particular COM port. There may or may not be jumpers that allowyou to set the Base I/O Address and IRQ to be used by the modem aswell.
  2. If the modem is configured for a COM port number that is assigned toa COM port on the motherboard or a serial card (physical port), youmust either set the modem to use a different COM port, or use theBIOS setup to disable the COM port with the same number as theinternal modem. For example, if both the internal modem and thephysical COM port are set to COM1, you must either set the internalmodem to a different, unused COM port, or the physical COM1 portmust be disabled in the BIOS setup.
  3. Make sure there are no other adapters or devices that are configuredfor the same Base I/O Address or IRQ as the internal modem. UsuallyCOM3, using an IRQ (or interrupt) of 5, is a good choice for aninternal modem. However, if you have a sound card, you may need tochoose a different IRQ than 5 since many sound cards use thatinterrupt.
  4. In the Ports component of Control Panel, verify that the IRQsettings and the I/O addresses are correct. Check the System logwith the Event Viewer for I/O or IRQ conflict errors.

    When possible, use standard settings for COM ports, which are asfollows:
             SERIAL 1   COM1:  I/O Address = 3F8h   IRQ = 4         SERIAL 2   COM2:  I/O Address = 2F8h   IRQ = 3         SERIAL 3   COM3:  I/O Address = 3E8h,  IRQ = 4         SERIAL 4   COM4:  I/O Address = 2E8h,  IRQ = 3						
  5. You do NOT need to add a new port in the Control Panel Ports appletto add support for an internal modem. NTDETECT will detect theinternal modem and the COM port it is configured to use. If aduplicate port was added using the Add button in the Control PanelPorts applet, use the Delete button to remove the duplicate port.
  6. Verify that the internal modem is not defective. Also, it is often agood idea to check with the vendor of your modem to see if there isa flash upgrade available for your modem.

Troubleshoot with HyperTerminal

Verify that Windows NT recognizes your modem and that you can dial outusing the HyperTerminal program. To do so, follow these steps:

NOTE: Before attempting to use HyperTerminal, verify that the RemoteAccess Server service is not running. Double-click the Services iconin Control Panel and verify that the Status column next to RemoteAccess Server is blank. If it displays "Started," click the Stop buttonto disable the Remote Access Server service before continuing.
  1. Click Start, point to Programs, point to Accessories, point toHyperTerminal, and then click HyperTerminal.
  2. When the New Connection Wizard is displayed, click Cancel.
  3. On the File menu, click Properties, and then click the modem you wantto test to select it in the Connect Using list.
  4. Click Configure, verify that your modem is set to use the correct port,and then click OK.
  5. Type "AT" (without quotation marks) in the HyperTerminal window, andthen press ENTER.
  6. If "AT" (without quotation marks) is displayed in the HyperTerminalwindow as you type it and "OK" (without quotation marks) is displayedafter you press ENTER, HyperTerminal recognizes the modem properly.If "AT" is not displayed as you type it or if "OK" is not displayedafter you press ENTER, review the previous steps in this article toverify that your modem is installed properly in Windows NT.
  7. Verify that your modem can dial out using HyperTerminal. On the Filemenu, click New Connection, and then follow the instructions on yourscreen.
  8. Click Dial. If the modem's speaker is enabled, you should hear a dialtone and the sound of the modem dialing the phone number.
For additional information, please see the following article(s) in theMicrosoft Knowledge Base:
ARTICLE-ID: 131868
TITLE : Troubleshooting PCMCIA Modems in Windows NT 3.51

ARTICLE-ID: 150808
TITLE : Disabling Remote Access Support for Unimodem Modems
connecting ras dialin tshoot

Article ID: 161516 - Last Review: 12/04/2015 16:02:36 - Revision: 1.1

Microsoft Windows NT Workstation 4.0 Developer Edition, Microsoft Windows NT Server 4.0 Standard Edition

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