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