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