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