feedback frame input terminal means for supplying said {TAIL ~ feedback frame} transmitted by said {HEAD ~ receiver} 
feedback frame input terminal means for supplying said { TAIL ~ feedback frame } transmitted by said { HEAD ~ receiver }
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD