One of the tape guide rollers, roller R6 is coupled to an optical tachometer encoder disk 80 which generates signal patterns in {HEAD ~ relation} to {TAIL ~ actual tape velocity} in the forward 26 and reverse 28 tape directions 
One of the tape guide rollers , roller R6 is coupled to an optical tachometer encoder disk 80 which generates signal patterns in { HEAD ~ relation } to { TAIL ~ actual tape velocity } in the forward 26 and reverse 28 tape directions
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH