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