The system also includes {HEAD ~ a pressure differential switch} which senses {TAIL ~ a drop} in pressure across a pedal valve 
senses
The system also includes { HEAD ~ a pressure differential switch } which senses { TAIL ~ a drop } in pressure across a pedal valve
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH