Modems Do Not Answer as RAS Server

• Microsoft Windows NT Server version 4.0
• Microsoft Windows NT Workstation version 4.0

SYMPTOMS

The Remote Access Service (RAS) server starts and a client rings, but the modem attached to the server does not pick up.

CAUSE

Windows NT 4.0 RAS services and Windows 95 Dial-Up Networking do not use the automatic answer mode because these services use Telephony Application Programming Interface (TAPI). They are polling for modem response RING and sending an ATA to manually answer (immediately pick up). This is necessary to let more than one application use the modem simultaneously. When you try to reproduce this procedure manually with a terminal program, an error results instead of the pick up. Thus, it is a problem with the modem.

WORKAROUND

To work around this problem, you can try either of the two methods depending on your modem.

Method One

To work around this problem with a Hayes modem, you can make changes like those shown in the following example by modifying an entry in %SystemRoot%\Inf\Mdmhayes.inf.

Before you modify the entries, you should copy and save the original .inf files with another name or to a different folder. You may want to restore the original files if this workaround does not work well.

In the [M1806Reg] section, make the following change:

Change: HKR, Init, 2,, "AT&FE0V0W1&C1&D2S95=47<cr>"

To: HKR, Init, 2,, "AT&FE0V0W1&C1&D2S95=47S40=6<cr>"

Method Two

Another way to work around this problem with US Robotics modems is to make changes like those shown in the following example. You can modify some entries in:

   %SystemRoot%\Inf\Mdmusrcr.inf for Courier modems.
   %SystemRoot%\Inf\Mdmusfr.inf for French modems.
   %SystemRoot%\Inf\Mdmusrg.inf for German modems.
   %SystemRoot%\Inf\Mdmusrsp.inf for Sportster modems.

In the [USRSP] section of Mdmusrsp.inf or Mdmusrg.inf, or in the [MfgAddReg] section of Mdmusrcr.inf or Mdmusfr.inf:

Change: HKR, Hangup, 1,, "ATH<cr>"

        HKR, Answer, 1,, "ATA<cr>"
        HKR,, Reset,, "ATZ<cr>"

    HKR, Answer, 1,, "ATS0=1<cr>"
    HKR,, Reset,, "ATS0=0Z<cr>"

MORE INFORMATION

The changes for the second workaround will switch the modem to the automatic answer mode only when the modem is ringing, and back to the normal mode if the application hangs up or resets the modem. Therefore, the modem should not have a problem serving more than one application at a time. However, this workaround does not work with applications that use the automatic answer mode for themselves.

For additional information on creating, modifying, and working methods of Mdmxxx.inf, please see the following Modem Development Kit available on MSDN (DDK for Windows 95) or the Microsoft anonymous ftp server:

   File Name: Modmdev.exe
   Location : ftp://ftp.microsoft.com/bussys/winnt/winnt-docs/papers/