detecting {HEAD ~ positions} of {TAIL ~ the image bearing belt} using a first sensor and a second sensor disposed in a different position from that of the first sensor; and 
of
detecting { HEAD ~ positions } of { TAIL ~ the image bearing belt } using a first sensor and a second sensor disposed in a different position from that of the first sensor ; and
OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH