A connection in the LINECALLSTATE_DIALTONE call state does not work as expected in Windows XP (840174)

SYMPTOMS

You may experience one or both of the following symptoms when you use the Unimodem 5 telephony service provider in Microsoft Windows XP.

Symptom A

If a connection is put in the LINECALLSTATE_DIALTONE call state after a lineDial function message is sent, the lineDrop function does not disconnect the call.

Symptom B

If a connection is already in the LINECALLSTATE_DIALTONE call state when the lineDial function is called, a PHONE_CLOSE message is sent, and the phone device handle is no longer valid.

CAUSE

Cause A

This problem in symptom A occurs because the lineDrop function does not expect the connection to be in the LINECALLSTATE_DIALTONE call state after a lineDial function message is sent. Therefore, an error occurs when the lineDrop function is called.

Cause B

This problem in symptom B occurs because an IOCTL_MODEM_GET_DLE command that is sent by the Unimdmat.dll file does not complete correctly. Therefore, the Unimodem service processes this command as a failure of either the hardware or the driver. In response, the Unimdmat.dll file sends a PHONE_CLOSE message to the Telephony API (TAPI) program.

RESOLUTION

Service pack information

To resolve this problem, obtain the latest service pack for Microsoft Windows XP. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

322389 How to obtain the latest Windows XP service pack

Hotfix information

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows XP service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

File information

The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel. Windows XP, 64-bit editions

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   08-Jun-2004  16:40  5.1.2600.1539     459,264  Unimdm.tsp
   08-Jun-2004  16:28  5.1.2600.1539     190,464  Wunimdm.tsp

Windows XP, 32-bit editions

 
   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   08-Jun-2004  16:28  5.1.2600.1539     190,464  Unimdm.tsp

MORE INFORMATION

Universal modem driver (Unimodem)

The universal modem driver (Unimodem) provides services for data modems, for fax modems, and for voice modems. These services are provided so that users and software developers do not have to learn or maintain modem Attention (AT) commands. AT commands are used to dial, to answer, and to configure modems. Unimodem performs these tasks by using files that specify the AT command sets and that specify the expected responses for modems. These files typically have a file name extension of .inf. Unimodem supports both voice and data. Therefore, a modem can be used as a speaker phone, as an answering machine, for data and fax functions, and for other useful purposes.

Telephony API (TAPI)

The Telephony API (TAPI) program is a set of Microsoft Win32 function calls and Component Object Model (COM) interfaces that are used by telephony applications. These function calls are processed internally by TAPI and cause calls to service providers that control the hardware that the telephony program requires.

Microsoft Windows XP Professional includes the following TAPI versions that are compatible with earlier versions:

TAPI 3.1 is compatible with TAPI 3.0.
TAPI 2.2 is compatible with TAPI 2.1.