�1���� Introduction
�2����
References
�3����
Definitions
�4����
Abbreviations
�5����
Line signals
������� 5.1���� Carrier frequency and modulation rate
������� 5.2���� Transmitted spectrum
������� 5.3���� Audio frames
������� 5.4���� Data-only coding
������� 5.5���� Audio plus data coding
������� 5.6���� Control segment encoding
������� 5.7���� Multiplexing/demultiplexing of data and control segments
�6����
Interfaces
������� 6.1���� DTE interface
������� 6.2���� Audio interface
�7����
Scrambler and descrambler
������� 7.1���� Scrambler/descrambler allocation
�8����
Operating procedures
������� 8.1���� Call establishment, capabilities exchange, and mode selection
procedures
������� 8.2���� V.25 automatic answering sequence
������� 8.3���� Symbol rate determination signal
������� 8.4���� Channel holding signal
������� 8.5���� Round trip delay estimating signals
������� 8.6���� Receiver conditioning signal
������� 8.7���� Rate signal
�9����
Start-up procedure
������� 9.1���� Call mode modem
������� 9.2���� Answer mode modem
10���� Retrain procedure
������ 10.1���� Call mode modem
������ 10.2���� Answer mode modem
������ 10.3���� Operation of circuits 107 and 109 during retrain procedure
11���� Rate renegotiating procedure
������ 11.1���� Initiating procedure
������ 11.2���� Responding procedure
12���� Testing facilities