An application can open a number of lines as well as negotiate API and extension versions. The application can call the lineOpen function with LINECALLPRIVILEGE_MONITOR privilege, meaning that it will only monitor, not own, incoming calls on all the lines opened.
An application could open a line with the intent of owning incoming calls by specifying LINECALLPRIVILEGE_OWNER as the privilege and a media mode other than NONE. The application could actually specify a number of media modes in this parameter by OR-ing the bit flags for each of the desired media modes. In that case, the application would be notified of incoming calls in any of the specified media modes, and it receives those calls as their owner. (Actually, another application that is also registered to receive calls of that media mode would receive the call instead, if it has a higher priority as designated in the registry.) This notification arrives in a call-state message that specifies, among other information, which line is carrying the incoming call. For example, by specifying LINEMEDIAMODE_INTERACTIVEVOICE, the application would be notified of incoming calls of the interactive voice media type (voice calls with a person on the local end of the line).