CONTENTS

 1     Scope
 2     References
 3     Definitions
 4     Abbreviations
 5     Requirements/Principles
 6     Conceptual Model
 7     Network Architecture
        7.1     E1-Network
        7.2     T1-Network
 8     International Switching Centre
 9     External Echo Control Device
10     ECD control channel
       10.1     E1-Network
                 10.1.1     Requirements for the control channel equipment
                 10.1.2     Coding
       10.2     T1-Network