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