The method 21, further comprising detecting errors in the signals at a receiving terminal, when no error is detected transmitting {HEAD ~ positive acknowledgment} from {TAIL ~ a receiving terminal}, and otherwise sending negative acknowledgments 
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The method 21 , further comprising detecting errors in the signals at a receiving terminal , when no error is detected transmitting { HEAD ~ positive acknowledgment } from { TAIL ~ a receiving terminal } , and otherwise sending negative acknowledgments
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 HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH