{HEAD ~ A tachometer module} 81 generates a collimated light beam which passes through the encoder disk 80 to a photodetector array which puts out electrical signals in quadrature relationship indicative of both velocity and direction of movement of {TAIL ~ the tape} 20 
{ HEAD ~ A tachometer module } 81 generates a collimated light beam which passes through the encoder disk 80 to a photodetector array which puts out electrical signals in quadrature relationship indicative of both velocity and direction of movement of { TAIL ~ the tape } 20
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH