Correlating Important Events › Understanding Configuration Manager › Configuration and Diagnostics › Voice - TAPI Issues

Voice - TAPI Issues

This section provides configuration and diagnostics information for the TAPI voice protocol. Consider the following items:

• TAPI is used for the telephony services that Windows provides. A program must initialize TAPI and shut it down when finished. TAPI can be initialized many times in the same program or another program. For all the TAPI initialize calls on the entire machine, there must be an equal number of TAPI shutdown calls. When TAPI is no longer in use by any program, the final shutdown does not free all resources in the TAPI service. If UNS_VOICES is the only program that uses TAPI on the machine, each first initialization and final shutdown combination leaks memory.

  Microsoft has acknowledged this problem. The company determined that the changes required would impact the current design and therefore no fix was made. The problem happened on a Windows 2000 Server SP4 machine. Microsoft says that this memory leak does not exist on Windows XP and will not exist in future Windows versions. See the Microsoft knowledge base article titled “A memory leak occurs in the Svchost.exe process that hosts a TAPI in Windows 2000.”

  A workaround does not fully resolve the leak, but it decreases the rate at which the leak grows. Each time the UNS_VOICES library is loaded, TAPI is initialized. TAPI is shut down when the library is unloaded and is where the TAPI leak occurs, provided it is the last program that shuts TAPI down. While the library is loaded no leak occurs.

• Telephony cards are highly recommended over voice modems because they can usually process voices and analyze call progress. Notification Services supports the Intel Dialogic D/4PCI telephony card. Any telephony card that is Microsoft TAPI v2 compliant may work as well.

  In order for the Intel Dialogic D/4PCI telephony card to work properly with UNS_VOICES, the Dialogic Generation 2 Telephony Service Provider (TSP) and WAVE drivers must be installed after the card is installed. For information about installing the drivers, see Install Drivers for Telephony Cards (Voice protocol) in the online help.

• Windows provides a TAPI UNIMODEM Telephony Service Provider (TSP) that supports voice modems (except NT4, unless the manufacturer supplies their own TSP). Therefore as long as a voice modem works with TAPI, UNS_VOICES should work. UNS_VOICES depends on TAPI to report that a connection is established. When a call is made, most voice modem drivers are configured to report a connected state back to TAPI immediately, regardless of whether the call is answered or still ringing. After UNS_VOICES receives the connected event, it starts speaking the message. Therefore, if a recipient picks up the phone a few seconds later, they either miss the entire message or hear the end of it, depending on the message length.

  There is a workaround, but it is not straightforward and the interaction between UNS_VOICES and the recipient is not seamless. When TAPI makes a call, it initializes the voice modem with settings that are defined by the modem's INF registry setting. Most modems use the voice command settings +VRN and +VRA (although some use #VRN and #VRA):

  • +VRN is the “Ringback Never Appeared Timer” whose value is the time the modem waits for the first ring tone to occur before assuming the call has been answered. Voice modem manufacturers usually set +VRN to 0, which means the modem does not wait for a ring tone. This value needs to be greater than 0. A recommended value is 10, but this requires trial and error depending on the phone system.
  • +VRA is the “Ringback Goes Away Timer” whose value is the time the modem waits for silence between the one ring tone and the next before assuming the call has been answered. We recommend that you increase this value if it is 0.

  You can find descriptions of +VRN and +VRA at http://www.cisco.com/en/US/products/sw/accesssw/ps275/prod_command_reference09186a00801f6327.html.

  To change these settings:

  1. Launch regedit and expand the following registry key:

     HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96D-E325-11CE-BFC1-08002BE10318}

     Key enumerations for each modem on your system appear, starting with 0000.

  2. Expand the key for the voice modem you are going to specify to UNS_VOICES.

     Note: The key may be hard to find. Try reading the FriendlyName key value for each enumeration.

  3. Select the VoiceDialNumberSetup key.
  4. Find AT+VRN=0, and change it to 10. If AT+VRA=0, change that value, too.

  Voice modems are not designed to detect a human voice, therefore it is not possible to wait until the recipient answers the phone and says something. With this resolution, when a recipient answers the phone, the message may not be spoken immediately because the voice modem uses timers to determine when a ring-tone has not occurred. TAPI reports a connected state only after the voice modem determines there are no further ring tones.

  A program cannot set these values because after control is returned, TAPI reads the settings in the registry and therefore overrides any changes a program may have made.

• The following device is not supported:
  • US Robotics Sportster Voice 33.6 Faxmodem with Personal Mail

    FCC ID: CJE-0375

    FCC REG#: CJEUSA 20778-MM-E

    ATI1: D869

    ATI3: USRobotics Sportster Voice 33600 Fax RS Rev. 2.0

    ATI9: (1.0USR0007\\Modem\Sportster 33600 FAX/VOICE EXT)FF

Troubleshooting

• If an error occurs while using a voice modem or telephony device, make sure the device is connected properly and detected by Windows.
  • For a voice modem, choose Control Panel, Phone and Modem Options. On the Modems tab, highlight the modem being used and click Properties. On the Diagnostics tab, click the Query Modem button. The modem should respond with response codes and not return an error. If it returns an error, the modem needs to be configured properly on Windows before it can be used with the protocol driver.
  • For another telephony device, check the device's diagnostic or sample program (if any) to determine if the device is working properly. Resolve any problems before using the device with the protocol driver.
  • For an Intel Dialogic D/4PCI telephony card, run the sample program installed with the Intel Dialogic System Release software, talker32.exe (Program Files\Intel Dialogic System Software\Sample Programs\TAPI). This must work before you can use the device with the protocol driver.

More information:

Configuration and Diagnostics