If {HEAD ~ the detection signal} is outside {TAIL ~ the preselected range} of air pressure, the controller unit transmits an alert signal to a transmitter means for remote transmission of an alarm signal to an alarm means 
is outside
If { HEAD ~ the detection signal } is outside { TAIL ~ the preselected range } of air pressure , the controller unit transmits an alert signal to a transmitter means for remote transmission of an alarm signal to an alarm means
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH