Preferably a value of {TAIL ~ the calibration counter} is indicated, so that it can be read off particularly in {HEAD ~ the event} of servicing 
Preferably a value of { TAIL ~ the calibration counter } is indicated , so that it can be read off particularly in { HEAD ~ the event } of servicing
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH