During use, as {HEAD ~ dust} fills {TAIL ~ the bag}, the bag expands and impinges upon a first of the pressure sensors and then upon a second of the pressure sensors, and so on, thereby indicating a filling of the bag with dust 
During use , as { HEAD ~ dust } fills { TAIL ~ the bag } , the bag expands and impinges upon a first of the pressure sensors and then upon a second of the pressure sensors , and so on , thereby indicating a filling of the bag with dust
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH