Support for Outbound-Calling Applications

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Support for Outbound-Calling Applications

Telephony Application Services (TAS) implements support for outbound call notification by making use of Microsoft Message Queue (MSMQ).

In this architecture, a server-side application is responsible for receiving event notifications from the data tier (for example, Microsoft SQL Server Notification Services) and placing a message into the outbound message queue.

When TAS has an available outbound SALT interpreter, it extracts the message from the queue. The message contains the URL for the outbound application Start page. TAS makes an HTTP request for the page defined by the URL. The Start page in turn contains a MakeCall control that initiates the outbound call.

Note   The number of SALT interpreters available for outbound calls depends on the configuration of the telephony interface manager (TIM) software. See the manufacturer's documentation for instructions on how to install and configure TIM software.

The full message flow can be seen in Figure 1 below.

Note   TAS fetches the requested URL only if the URL is in the Trusted Sites list for TAS. (See Adding or Removing a Trusted Site.) TAS can be configured to receive messages from only a single queue. See the section on Configuring Speech Server for Outbound Calling.

Message flow for outbound calling

Figure 1: Message flow for outbound notifications

In this architecture, the speech application is responsible for posting back state information about the progress of the outbound call, once the call is initiated. The Business Logic tier is then responsible for re-queuing any failed call notification requests. Failures should be determined by the speech application and these typically fall into the following categories:

  • Called party does not answer.

  • Called party is busy.

  • Call is answered by voicemail.

  • Dialog interaction with the called party did not reach a critical point, for which success is defined in the application.

  • System errors that prematurely end the call or even stop the call from being made.

See Also

Setting up a Message Queue | Configuring Speech Server for Outbound Calling | Message Queuing Overview