Thus, during a portion, Δ, of each period P, there is {TAIL ~ a dead zone} during which both transistors Q1 and Q2 are in non conducting {HEAD ~ condition} 
Thus , during a portion , Δ , of each period P , there is { TAIL ~ a dead zone } during which both transistors Q1 and Q2 are in non conducting { HEAD ~ condition }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD