Therefore this circuit produces a digital ramp signal with {HEAD ~ a slope} and frequency proportional to the numerical value of {TAIL ~ the input digital word} 
Therefore this circuit produces a digital ramp signal with { HEAD ~ a slope } and frequency proportional to the numerical value of { TAIL ~ the input digital word }
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 TAIL TAIL