Applications can become aware of existing calls on the line at the time of application startup with lineGetNewCalls. This function gives the application handles using monitor privilege to all the calls on the line or address for which it did not already have handles.
An example of the usefulness of this mechanism is when a user starts a fax application during a voice call, having decided to send a fax. The new fax application needs to discover the existing call (using lineGetNewCalls) to request ownership of the call in order to send the fax.