CONTENTS

1 Introduction
2 Signalling rates
2.1 Data signalling rates
2.2 Signalling rates on line
3 Differentiation between user and network data signals
3.1 Scrambler (64 kbit/s only)
3.2 Descrambler (64 kbit/s only)
4 Interfaces
4.1 V.24-type interface
4.2 X.24-type interface
5 Rate adaptation
6 Testing facilities
6.1 Test loops
6.2 Self tests
7 Multiplexing
8 Internal management
Appendix I Functional block diagram
Appendix II Connection schematic
Appendix III Rate adaptation of data signalling rates below 48 kbit/s
III.1 Data signalling rates
III.2 Rate adaptation
III.3 Interfaces
Appendix IV Example of implementation of the transmission unit
IV.1 General
IV.2 Physical model of the line transmission system
IV.3 Functional description of the DCE
IV.4 Functions of TU functional block
IV.5 Requirements for a line transmission system using 2B1Q line code
IV.6 DCE management channel
IV.7 Equipment management function