Figure : 1. Station-to-station calls on the same server
In the figure, the server uses the service domains and the precedence levels to treat calls as follows:
User C makes a routine call to user B and is still connected. The server checks the service domain of the COR of user C, and assigns service domain 2 to the call.
User A makes an immediate precedence call to user B. The server checks the service domain of the COR of user A, and assigns service domain 2 to the call.
The server matches the service domain of user C with the service domain of user A.
Because the calls are in the same service domain, and because user A used a higher precedence level than user C, the server allows user A to preempt the call of user C.