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