Various circuits are described to generate {HEAD ~ the Q.E.D. signal} and the essential properties of {TAIL ~ the signal} are defined 
Various circuits are described to generate { HEAD ~ the Q.E.D. signal } and the essential properties of { TAIL ~ the signal } are defined
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH