CONTENTS

 1     Introduction
        1.1     Scope
        1.2     Reference configuration
 2     Physical media characteristics at the S_B reference point for 25 600 kbit/s physical layer interface
        2.1     Transmission link requirements
                  2.1.1     Line and bit rates
                  2.1.2     Bit rate symmetry
                  2.1.3     Bit Error Ratio (BER)
                  2.1.4     Transmission link timing
                  2.1.5     Free running timing configurations
        2.2     Transmitter requirements
                  2.2.1     Transmitter zero-crossing distortion
                  2.2.2     Transmitter waveshapes
                  2.2.3     Transmitter launch amplitude
                  2.2.4     Transmitter return loss
        2.3     Receiver requirements
                  2.3.1     Receiver acquisition timing
                  2.3.2     Receiver return loss
        2.4     Copper link segment characteristics
                  2.4.1     100 ohm link segment
                  2.4.2     120 ohm link segment
                  2.4.3     150 ohm link segment
 3     Functions provided by the transmission convergence sublayer
        3.1     Cell scrambling and descrambling
                  3.1.1     PRNG sequence
        3.2     4B5B block coding and decoding
                  3.2.1     Symbol-pair level code structure
                  3.2.2     Cell delineation
                  3.2.3     Support for a timing signal
        3.3     NRZI encoding and decoding
        3.4     HEC generation and verification
 4     References
 5     Bibliography
 6     Definitions
 7     Abbreviations