Transfer voice element performs a call transfer to
a phone number specified by a configuration setting. Depending on how the voice
browser is configured, the call transfer can be a bridge transfer or a blind
transfer. For a bridge transfer, the voice browser makes an outbound call while
maintaining the original call and acts as a bridge between the two calls. The
advantage of this is that once the secondary call ends, the original call can
still continue with the IVR. The disadvantage is that two separate phone lines
are used. For a blind transfer, the voice browser makes an outbound call and
when connected, links the original call to the new caller through the use of a
telephony switch. At this point, the voice browser (and as a result VXML
Server) is no longer in control of the call. Blind transfers involve only one
The Transfer element defines exit states for the different ways
bridge transfers can end such as the person being called hung up, there was no
answer, there was a busy signal, or some other phone-related error occurred.
Since blind transfers take the call away from the voice browser and VXML
Server, a Transfer element performing a blind transfer would never return an
exit state. Instead, an special event would be thrown by the voice browser,
caught in the root document for the call, and VXML Server would terminate the
session by interrupting the Transfer element.
The number to transfer to can be any phone number allowed by the
voice browser telephony provider (some may place restrictions on outbound
dialing). Please note that different voice browsers may or may not accept
certain kinds of phone numbers. Check your voice browser documentation for
specific requirements and restrictions for call transfer.