Hi, The Lines | Manage screen has a column for: - Identification - Virtual Extension Then, when you VIEW a line, you don't see these two fields any more. However, there ARE two input fields called: - External Number - Internal Number It appears as if Identificaton=External Number and Virtual Extension=Internal number. But that still doesn't tell me HOW these numbers are being used, how to choose the correct or most appropriate values for these number, how they are different from each other... what is the effect if I change one number, or the other? What do these numbers tie into (e.g., if I change a number, what other part of the system will I have to change to "match" that number). I tried to find some "guidance" in the manual, but either I didn't look correctly or it isn't there. I also tried to search the forum, but it won't let me search for "external internal number lines".