If answer is detected, the adapter monitors for call termination and {HEAD ~ the initiation} of {TAIL ~ a new call} 
of
If answer is detected , the adapter monitors for call termination and { HEAD ~ the initiation } of { TAIL ~ a new call }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL