substituting means for substituting {HEAD ~ a second portion} of said feedback frame with {TAIL ~ said second predetermined bit stream} upon determining that said first portion of said feedback frame consists of said first predetermined bit stream; and 
substituting means for substituting { HEAD ~ a second portion } of said feedback frame with { TAIL ~ said second predetermined bit stream } upon determining that said first portion of said feedback frame consists of said first predetermined bit stream ; and
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL 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