if the selection corresponds to the first entry, executing a set of {HEAD ~ voice exchange operations} to initiate {TAIL ~ the voice exchange session} using a value of the first entry; and 
if the selection corresponds to the first entry , executing a set of { HEAD ~ voice exchange operations } to initiate { TAIL ~ the voice exchange session } using a value of the first entry ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH