CONTENTS

 1     Scope
 2     References
 3     Definitions
 4     Abbreviations
 5     System reference diagram
 6     Signals and modulation
        6.1     Description of signals
                  6.1.1     4.3125 kHz signalling family
                  6.1.2     4 kHz signalling family
        6.2     Modulation
 7     Description of messages
        7.1     CL – Capabilities List
        7.2     CLR – Capabilities List + Request
        7.3     MR – Mode Request
        7.4     MS – Mode Select
        7.5     ACK(1) – Acknowledge, Type 1
        7.6     ACK(2) – Acknowledge, Type 2
        7.7     NAK-EF – Negative Acknowledge, Errored Frame
        7.8     NAK-NR – Negative Acknowledge, Not Ready
        7.9     NAK-NS – Negative Acknowledge, Not Supported
       7.10     NAK-CD – Negative Acknowledge, Clear Down
       7.11     REQ-MS – Request MS Message
       7.12     REQ-MR – Request MR Message
       7.13     REQ-CLR – Request CLR Message
 8     Structure of messages
        8.1     Format convention
        8.2     Frame structure
        8.3     Frame check sequence field
        8.4     Octet transparency
        8.5     Inter-frame time fill
 9     Message coding format
        9.1     General
        9.2     Coding format for parameters in the I and S fields
                  9.2.1     Parameter classification
                  9.2.2     Order of transmission of parameters
                  9.2.3     Delimiting and parsing of parameter blocks
        9.3     Identification field (I)
                  9.3.1     Message type
                  9.3.2     Revision number
                  9.3.3     Vendor ID field
                  9.3.4     Parameter field
        9.4     Standard information field (S)
        9.5     Non-standard information field (NS)
        9.6     Overall message composition
10     G.994.1 transactions
       10.1     Basic transactions
                 10.1.1     Transaction A
                 10.1.2     Transaction B
                 10.1.3     Transaction C
       10.2     Extended transactions
                 10.2.1     Transaction A:B
                 10.2.2     Transaction B:A
                 10.2.3     Transaction A:C
                 10.2.4     Transaction B:C
       10.3     Message segmentation
       10.4     State transition diagrams
11     Start-up/cleardown procedures
       11.1     Duplex start-up procedures
                 11.1.1     HSTU-R initiated start-up procedure
                 11.1.2     HSTU-C initiated start-up procedure
       11.2     Half-duplex start-up procedures
                 11.2.1     HSTU-R initiated start-up procedure
                 11.2.2     HSTU-C initiated start-up procedure
       11.3     Cleardown procedure
12     Error recovery procedures
Annex A – Support for Legacy non-G.994.1  Devices
Appendix I – G.994.1 sample sessions
Appendix II – Provider code contact information
Appendix III – Support for Legacy DMT-based Devices
Appendix IV – Procedure for the assignment of additional G.994.1 parameters
       IV.1     Introduction
       IV.2     Procedure
Appendix V – Bibliography