The control software also allows automatic distributed operation of multiple sites in {HEAD ~ synchronization} to within {TAIL ~ parts} per million or better 
to within
The control software also allows automatic distributed operation of multiple sites in { HEAD ~ synchronization } to within { TAIL ~ parts } per million or better
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH