CONTENTS

 1     Scope
 2     References
 3     Definitions
 4     Abbreviations
 5     Digital modem
 6     Analogue modem
        6.1     Data signalling rates
        6.2     Symbol rate
        6.3     Scrambler
        6.4     Transmitter
                  6.4.1     Modulus encoder
                  6.4.2     Precoder and prefilter
                  6.4.3     Inverse map
                  6.4.4     Convolutional encoder
 7     Interchange circuits
        7.1     List of interchange circuits
        7.2     Asynchronous character-mode interfacing
 8     Signals and sequences
        8.1     Full Phase 1
        8.2     Short Phase 1 signals and sequences for the analogue modem
                  8.2.1     QC1a
                  8.2.2     QC2a
                  8.2.3     QCA1a
                  8.2.4     QCA2a
                  8.2.5     TONEq
        8.3     Short Phase 1 signals and sequences for the digital modem
                  8.3.1     ANSpcm
                  8.3.2     QC1d
                  8.3.3     QC2d
                  8.3.4     QCA1d
                  8.3.5     QCA2d
                  8.3.6     QTS
        8.4     Full and short Phase 2 signals and sequences
                  8.4.1     INFO information bits
        8.5     Phase 3 signals for the analogue modem
                  8.5.1     CP_t
                  8.5.2     E_1u
                  8.5.3     MD
                  8.5.4     J_a
                  8.5.5     R_u
                  8.5.6     S_u
                  8.5.7     TRN_1u
        8.6     Phase 3, signals for the digital modem
                  8.6.1     DIL
                  8.6.2     J_d
                  8.6.3     J_p
                  8.6.4     J_p´
                  8.6.5     R_i
                  8.6.6     SCR
                  8.6.7     S_d
                  8.6.8     TRN_1d
        8.7     Phase 4, Rate Renegotiation and Fast Parameter Exchange signals for the analogue modem
                  8.7.1     B1_u
                  8.7.2     E_2u
                  8.7.3     CP_u
                  8.7.4     R_M
                  8.7.5     SUV_u
                  8.7.6     TRN_2u
                  8.7.7     FB1_u
        8.8     Phase 4, Rate Renegotiation and Fast Parameter Exchange signals for the digital modem
                  8.8.1     B1_d
                  8.8.2     E_d
                  8.8.3     CP_d
                  8.8.4     R
                  8.8.5     SUV_d
                  8.8.6     TRN_2d
        8.9     Modem-on-hold
                  8.9.1     RT
                  8.9.2     MH sequences
 9    Operating procedures
        9.1     Full Phase 1 – Network interaction
        9.2     Short Phase 1 – Network interaction
                  9.2.1     Call modem is analogue modem
                  9.2.2     Call modem is digital modem
                  9.2.3     Answer modem is analogue modem
                  9.2.4     Answer modem is digital modem
                  9.2.5     ODP/ADP bypass
        9.3     Full Phase 2 – Probing/ranging
                  9.3.1     ODP/ADP bypass
        9.4     Short Phase 2 – Ranging
                  9.4.1     Digital modem
                  9.4.2     Analogue modem
        9.5     Phase 3 – Equalizer and echo canceller training and digital impairment learning
                  9.5.1     Digital modem
                  9.5.2     Analogue modem
        9.6     Phase 4 – Final training
                  9.6.1     Digital modem
                  9.6.2     Analogue modem
        9.7     Retrains
                  9.7.1     Digital modem
                  9.7.2     Analogue modem
        9.8     Rate renegotiation
                  9.8.1     Digital modem
                  9.8.2     Analogue modem
        9.9     Fast parameter exchange
                  9.9.1     Digital modem
                  9.9.2     Analogue modem
       9.10     Modem‑on‑hold
                 9.10.1     Transmission of MH sequences
                 9.10.2     Modem‑on‑hold transactions
       9.11     Cleardown
10     Testing facilities