A voltage controlled oscillator is supplied with a part of the output of {HEAD ~ the phase comparator} which controls {TAIL ~ its oscillation frequency} 
controls
A voltage controlled oscillator is supplied with a part of the output of { HEAD ~ the phase comparator } which controls { TAIL ~ its oscillation frequency }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL