detecting and saving {HEAD ~ a called extension number} sent by {TAIL ~ said central office} from a calling party on a direct in dial trunk line into said PBX, 
sent by
detecting and saving { HEAD ~ a called extension number } sent by { TAIL ~ said central office } from a calling party on a direct in dial trunk line into said PBX ,
OTH OTH OTH HEAD HEAD 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