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