Before placing a call, an application must establish a means of communication between itself and TAPI. The application must select a telephony event notification mechanism, and specify this in a call to the lineInitializeEx function. One of the values lineInitializeEx returns is the number of line devices available to the application. In this example, that number is one, and the line's identifier in telephony's zero-based scheme is 0. The application must establish this communication link (with lineInitializeEx) regardless of the type of call to be placed or received.