A cycle is defined by repeatedly developing {HEAD ~ a start signal} at the beginning of {TAIL ~ each cycle} 
A cycle is defined by repeatedly developing { HEAD ~ a start signal } at the beginning of { TAIL ~ each cycle }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL