The controller inserts a five digit prefix, {TAIL ~ namely the access code} into {HEAD ~ the dialed number} 
The controller inserts a five digit prefix , { TAIL ~ namely the access code } into { HEAD ~ the dialed number }
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD