Outgoing Call Complete

Hi,
I have the following scenario ....
-- Im making a outgoing call, where in i dial the number and press the "green" button, then you observe that the phone is ringing on the other side(recipient),by
means of the UI in the phone.

-- Now the receiver picks the call, which can be observed at the caller's terminal UI .This usually shows the "Time elapsed" indicator .

My question - Where exactly do i need to tap the signal on the caller terminal , when the receiver picks the call. Consider i'm using a S60 phone.
i.e which part of the code does the UI switch( from a ringing indicator to time elapsed indicator).