It is convenient for {HEAD ~ the user} to know the remaining toner, {TAIL ~ the photo conductor life}, etc 
to know
It is convenient for { HEAD ~ the user } to know the remaining toner , { TAIL ~ the photo conductor life } , etc
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH