The apparatus includes each timing server of the multiple pluralities of {HEAD ~ timing servers} configured to transmit, receive, and monitor {TAIL ~ synchronization signals} 
configured to transmit
The apparatus includes each timing server of the multiple pluralities of { HEAD ~ timing servers } configured to transmit , receive , and monitor { TAIL ~ synchronization signals }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL