By inserting {HEAD ~ the access code} into {TAIL ~ the dialed number} the device selects a particular long distance carrier for the duration of the call 
By inserting { HEAD ~ the access code } into { TAIL ~ the dialed number } the device selects a particular long distance carrier for the duration of the call
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH