The transducer produces {HEAD ~ an output electrical signal} proportional to {TAIL ~ the extent} to which the third laser beam energy is absorbed by the propane gas 
proportional to
The transducer produces { HEAD ~ an output electrical signal } proportional to { TAIL ~ the extent } to which the third laser beam energy is absorbed by the propane gas
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH