Troubleshooting Communications Problems

This section describes how to solve problems with installing modems, making connections, and using applications to access the modem. Windows 95 provides a troubleshooter for modems in online Help. Try using this troubleshooter before trying the troubleshooting steps included in this section. In addition, a general modem diagnostic tool is located in the Modems option in Control Panel. It provides information about each modem and COM port that have been configured on the computer.

To use the Modems Diagnostics Tool

  1. In the Modems option in Control Panel, click the Diagnostics tab.
  2. In Diagnostics properties, click the Driver button to find out which communications driver is installed for Win16-based communications APIs. For these applications, the driver should be COMM.DRV. If a different driver is listed and you are having problems with using Win16-based applications, the driver is probably the cause.
  3. In Diagnostics properties, click the More Info button to make sure Windows 95 can communicate with the modem. Clicking this button causes Windows 95 to send commands to and read responses from the modem, and then to display information about the modem and its COM port.

    The Port Information box displays the following information:

    • The IRQ and I/O address of the modem's COM port. These should match the physical configuration of the port or modem adapter.
    • The UART type of the COM port, for example, 8250 or 16550A. Notice that 16550A UART ports can sustain faster connection speeds with fewer errors.
    • The highest port speed supported by the modem. Never set the modem's speed higher than the speed listed here.

    The Modem Information box displays the modem's responses to various AT commands that Windows 95 previously sent to it. Some modems return a response that indicates what make and model it is. This can help you select the correct modem if the Install New Modem wizard did not detect it correctly. Notice that many modems return "ERROR" for some AT commands. This means that the modem does not support that particular AT command.

The Record a Log File option in the Modems option also helps you identify modem problems by recording modem commands and responses in a MODEMLOG.TXT file as described in "Setting Modem Properties" earlier in this chapter.