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