a pressure sensor connected in {HEAD ~ line} with {TAIL ~ said distribution trunk tube} and adapted to sense and indicate normal and abnormal operating pressures; and 
a pressure sensor connected in { HEAD ~ line } with { TAIL ~ said distribution trunk tube } and adapted to sense and indicate normal and abnormal operating pressures ; and
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH