Responsive to the condition signal, the control part controls {HEAD ~ the announcing arrangement} at {TAIL ~ the particular time instant} 
at
Responsive to the condition signal , the control part controls { HEAD ~ the announcing arrangement } at { TAIL ~ the particular time instant }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL