Attended transfer is when a call is routed to a third party only if the third party answers the call.
To do this, Blueworx Voice Response makes a call to the third party. When the application is ready to perform the transfer, a REFER message containing a TO header and a REPLACES header identifying the third party, is sent to the original caller. The original caller then sends an INVITE message containing the REPLACES information to the third party. If the transfer is accepted, the original caller notifies Blueworx Voice Response and both calls will disconnect from Blueworx Voice Response.
For attended transfer, phones must support both the REFER method and the REPLACES header.