The first circuit uses {HEAD ~ the clock signal} received at the first input node to control the frequency of {TAIL ~ the oscillator} 
The first circuit uses { HEAD ~ the clock signal } received at the first input node to control the frequency of { TAIL ~ the oscillator }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL