US Patent 8050393 Method and apparatus for evaluating possible 3-way call events

The likelihood that a called party to a telephone call has forwarded the call to another party, or has conferenced the call to include another party is estimated by requiring that the called party supply a first signal, illustratively a first DTMF signal, later requiring that the called party provide a second signal, illustratively the same DTMF signal provided by the first signal, and comparing characteristics of said first and second signals as received at a telephone network node.