a control voltage source with a phase output and {TAIL ~ a neutral output} for supplying control voltage to {HEAD ~ said moment defining circuit} and said level changing circuit 
a control voltage source with a phase output and { TAIL ~ a neutral output } for supplying control voltage to { HEAD ~ said moment defining circuit } and said level changing circuit
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH