{HEAD ~ The pressure sensor} comprises either a door, whose movement is measured without contact, or {TAIL ~ a sensor}, whose movement is measured optically 
{ HEAD ~ The pressure sensor } comprises either a door , whose movement is measured without contact , or { TAIL ~ a sensor } , whose movement is measured optically
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH