In Cisco Unified Attendant Console operators have two options for call transfers. Blind and Consult. The major difference between these two transfer methods in technical terms is the Consult Transfer uses the Operator’s Phone CSS and the Blind Transfer uses the Service Queue’s (CTI) CSS. Most Engineers will configure the Operators handset to have the ability to call Internal and PSTN phone numbers. However, they neglect to give the same access to the Service Queue CTI Ports. In this scenario, the Operator would experience issues with attempting blind transfers to a PSTN Phone Number. The Console would return a “Invalid Destination” error and return the call to the Operator.
If you make a change to the CSS for the Service Queue CTI Port, you need to synchronise between CUAC and CUCM. Then to apply the changes, the CUAC Engine needs to be restarted from the Web Admin Console.