In other words, {HEAD ~ this sensor} can be located anywhere in the system downstream of a loading station for {TAIL ~ the pucks} 
In other words , { HEAD ~ this sensor } can be located anywhere in the system downstream of a loading station for { TAIL ~ the pucks }
OTH OTH OTH OTH 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