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