They occur at precise times in programming and can synchronize {TAIL ~ the operation} of receiver station apparatus to the timing of {HEAD ~ programming transmissions} 
They occur at precise times in programming and can synchronize { TAIL ~ the operation } of receiver station apparatus to the timing of { HEAD ~ programming transmissions }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD