The method 14 or 15 wherein {HEAD ~ the step} of selectively generating {TAIL ~ said signal} comprises the steps of: 
The method 14 or 15 wherein { HEAD ~ the step } of selectively generating { TAIL ~ said signal } comprises the steps of :
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH