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