There are two main reasons for using a trombone operation:
If the combination of switch and Blueworx Voice Response you are using cannot support transfer, you can use the trombone operation to simulate a transfer operation with a trombone operation. The connection is maintained until either the caller or the third party terminates the call by hanging up.
This has the disadvantage over a normal switch-based transfer operation that two Blueworx Voice Response channels are occupied for the whole time that the caller and third party are talking. With a switch-based transfer, the channel between the caller and Blueworx Voice Response is broken as soon as the caller is transferred to the third party.
The trombone allows the caller to consult with a third party. When the third party hangs up, or the caller terminates the consultation, the caller is connected back to Blueworx Voice Response at the point where they left the application they were using.
This might be useful in a voice mail application, for example, where a caller can break out to respond to an urgent voice mail message, then return to processing the rest of the voice mail after dealing with the urgent matter.