In step 507, bridging and signaling {HEAD ~ unit} 109 provides {TAIL ~ answer supervision} on the callers telephone call 
provides
In step 507 , bridging and signaling { HEAD ~ unit } 109 provides { TAIL ~ answer supervision } on the callers telephone call
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH