There is almost always {HEAD ~ more than one incoming DID trunk} or E&M tie line into {TAIL ~ a PBX} 
into
There is almost always { HEAD ~ more than one incoming DID trunk } or E&M tie line into { TAIL ~ a PBX }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL