Call transfer

Calls can be transferred to a human operator or another VoiceXML application. The different types of call transfer possible using VoiceXML with Blueworx Voice Response are described.

For blind transfer (when bridge=“false”), the VoiceXML browser simply initiates the call transfer request and then disconnects from the call; the system cannot verify whether the telephone number for the call transfer has been correctly configured in the telephony system. In addition, no information is returned on the status of the transfer, so there is no way to know whether the transfer was successful, the line was busy, the telephone number was invalid, or the call was dropped. The Blueworx Voice Response connection environment provides additional call transfer capabilities. For more information, refer to the Blueworx Voice Response for AIX documentation.

For bridged transfer (when bridge=“true”), a conference call is set up to include the person or application specified by the dest=attribute, known as the “Callee.”

The Blueworx Voice Response platform is not able to create a conference between itself, the Caller, and the Callee. Blueworx Voice Response must be configured with a suitable telephony service. See Blueworx Voice Response: Deploying and Managing VoiceXML and Java Applications for more information.

The telephony service allows Blueworx Voice Response to request that the conference be created by the telephony system to which Blueworx Voice Response is attached, as shown in the following figure.

Figure 1. Conference
This image shows Blueworx Voice Response requesting that a conference be created by the telephony system to which Blueworx Voice Response is attached.

This image shows Blueworx Voice Response requesting that a conference be created by the telephony system to which Blueworx Voice Response is attached.

This method of implementing a bridged transfer does not provide the same functionality as VoiceXML 2.1 because Blueworx Voice Response does not have control over the voice connections to the Caller and Callee separately. The differences are the following.

Either the Caller or the Callee may terminate the bridge by DTMF, or by a speech grammar match, because Blueworx Voice Response cannot distinguish the source of the match.
It is not possible for the Caller to terminate the bridge during the period of time where the telephony system is attempting to create the conference. Typically the Caller will hear “music on hold” that is generated by the Telephony system during this time period. Thus it is not possible for Blueworx Voice Response to support the transferaudio=attribute.
Blueworx Voice Response is not able to terminate the conference even if the bridge is terminated using a grammar match, and a script execution continues for the <transfer> element. It is necessary for either the Caller, Callee, or Blueworx Voice Response to disconnect in order to terminate the conference.

Note: What the user will hear if the transfer is unsuccessful depends on your central office and your telephony configuration. Even a standard setup on the telephony system may not provide consistent behavior from all central office service providers; depending on the information sent by the central office, a user might hear a busy signal, silence, or no answer.

One interesting way that you might use call transfer is to route calls to different language versions of the same application, based on the caller's DTMF response to an introductory, prerecorded audio prompt. For example:

System:

For English, press 1. Pour français, appuyez sur 2.

(Call will be transferred to the English application.)
(Call will be transferred to the French application.)

Note: You should not use TTS prompts or spoken input in this initial prompt, since these require the application to be running in the desired language version of the VoiceXML browser.

The two potential drawbacks of this design are:

You will not know if the transfer was unsuccessful.
You lose the ANI and DNIS information from the original call. (The ANI information for the transferred call is the IP address of the Voice Server that initiated the transfer. The DNIS information is the telephone number to which the call was transferred.)