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