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