The function of the private line eliminates the possibility of someone other than you reviewing your call details, from phone sets, which have the shared extension, additionally no one can monitor your call or connect to you call.
IDC projected over 9 billion minutes of voice traffic to travel over worldwide packet networks in 2000, exceeding 135 billion minutes in 2004. Service revenue is projected at 1.6 billion in 2000 and 18.7 billion in 2004.