The magnitude of delay is varied between {HEAD ~ these two extremes} by varying {TAIL ~ the relative levels} of operation of the differential sections D1 and D2 
The magnitude of delay is varied between { HEAD ~ these two extremes } by varying { TAIL ~ the relative levels } of operation of the differential sections D1 and D2
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH