The tractor sensing {HEAD ~ apparatus} 11 wherein the sensing means is {TAIL ~ a Hall effect sensor} 
The tractor sensing { HEAD ~ apparatus } 11 wherein the sensing means is { TAIL ~ a Hall effect sensor }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL