Troubleshooting Modem Problems Under Windows NT
4.0
Summary: This article describes procedures to help you diagnose and fix problems
when you are unable to dial out using your modem in Windows NT 4.0 with
Dial-Up Networking (DUN).
More Information:
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 following
procedures 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:
- In Control Panel, double-click Modems. The Install New Modem Wizard
starts automatically if you have not installed a modem before. If the wizard
does not start automatically, you have installed a modem previously and you
should click Add to start the wizard.
- Check the box labeled "Don't detect my modem; I will select it from a
list," and then click Next.
- In the Manufacturers box, click Standard Modem Types. In the Models
box, click a model that corresponds to the speed of your modem, and then
follow the instructions in the Install New Modem Wizard.
Verify Your COM Port(s)
Verify that Windows NT recognizes your COM port(s) by double-clicking the
Ports icon in Control Panel to see if the COM port that the modem is
connected 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, there is
most likely a hardware problem or a configuration problem. Use the
following steps to troubleshoot the problem.
External Modems
- If the COM port is on the motherboard or is provided by a serial card,
make sure the port is not disabled in the BIOS (also called the CMOS)
setup of the computer. Refer to the documentation for your computer to
obtain information about configuring options in the BIOS setup.
- Make sure there are no other adapters or devices that are configured
for the same Base I/O Address or IRQ as the COM port to which the modem is
attached.
- Verify that the serial port is not defective. If the modem and any
other serial devices fail on the COM port but work on other COM ports, and you
have verified the two steps above, the serial port may be defective.
- Verify the serial cable is not defective by using a new standard
serial
cable.
Internal Modems
- If the COM port is defined by an internal modem, make sure the jumpers
on the modem are configured properly. Internal modems will almost always
have a jumper on the adapter that configures the modem as a particular COM
port. There may or may not be jumpers that allow you to set the Base I/O
Address and IRQ to be used by the modem as well.
- If the modem is configured for a COM port number that is assigned to a
COM port on the motherboard or a serial card (physical port), you must either
set the modem to use a different COM port, or use the BIOS setup to
disable the COM port with the same number as the internal modem. For
example, if both the internal modem and the physical COM port are set to
COM1, you must either set the internal modem to a different, unused COM
port, or the physical COM1 port must be disabled in the BIOS setup.
- Make sure there are no other adapters or devices that are configured
for
the same Base I/O Address or IRQ as the internal modem. Usually COM3,
using an IRQ (or interrupt) of 5, is a good choice for an internal modem.
However, if you have a sound card, you may need to choose a different IRQ
than 5 since many sound cards use that interrupt.
- In the Ports component of Control Panel, verify that the IRQ settings
and the I/O addresses are correct. Check the System log with the Event Viewer
for I/O or IRQ conflict errors. When possible, use standard settings for
COM ports, which are as follows:
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
- You do NOT need to add a new port in the Control Panel Ports applet to
add support for an internal modem. NTDETECT will detect the internal modem
and the COM port it is configured to use. If a duplicate port was added using
the Add button in the Control Panel Ports applet, use the Delete button to
remove the duplicate port.
- Verify that the internal modem is not defective. Also, it is often a
good idea to check with the vendor of your modem to see if there is a flash
upgrade available for your modem.
Troubleshoot with HyperTerminal
Verify that Windows NT recognizes your modem and that you can dial out
using the HyperTerminal program. To do so, follow these steps:
NOTE: Before attempting to use HyperTerminal, verify that the
Remote Access Server service is not running. Double-click the Services icon in
Control Panel and verify that the Status column next to Remote Access Server is
blank. If it displays "Started," click the Stop button to disable the
Remote Access Server service before continuing.
- Click Start, point to Programs, point to Accessories, point to
HyperTerminal, and then click HyperTerminal.
- When the New Connection Wizard is displayed, click Cancel.
- On the File menu, click Properties, and then click the modem you want
to test to select it in the Connect Using list.
- Click Configure, verify that your modem is set to use the correct
port, and then click OK.
- Type "AT" (without quotation marks) in the HyperTerminal window, and
then press ENTER.
- If "AT" (without quotation marks) is displayed in the HyperTerminal
window as you type it and "OK" (without quotation marks) is displayed after you
press ENTER, HyperTerminal recognizes the modem properly. If "AT" is not
displayed as you type it or if "OK" is not displayed after you press
ENTER, review the previous steps in this article to verify that your modem
is installed properly in Windows NT.
- Verify that your modem can dial out using HyperTerminal. On the File
menu, click New Connection, and then follow the instructions on your screen.
Click Dial. If the modem's speaker is enabled, you should hear a dial tone
and the sound of the modem dialing the phone number.
Provided by Microsoft
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