{HEAD ~ filter regulator} means for filtering {TAIL ~ the air} entering the signal air path and for regulating the pressure in the signal air path to a predetermined pressure 
for filtering
{ HEAD ~ filter regulator } means for filtering { TAIL ~ the air } entering the signal air path and for regulating the pressure in the signal air path to a predetermined pressure
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL 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