CONTENTS

 1     Scope
 2     References
 3     Terms and definitions
 4     Abbreviations
 5     Bearer capabilities for which echo control is required
 6     Arrangements of echo control devices with respect to signalling
 7     Operation without signals
 8     Considerations for the need of ECDs
        8.1     Information taken into consideration
        8.2     Propagation delay counter, call history information
 9     Functions of an exchange initiating echo control
10     Unavailability of echo control devices
11     Placement of echo control devices in the network
12     Handling of echo control devices in the case of different bearer capabilities
13     Other considerations
Annex A - Echo control logic
        A.1     General principles and definitions
                  A.1.1     General principles
                  A.1.2     Definitions
        A.2     Abstract model
                  A.2.1     General description
                  A.2.2     Signalling system/protocol
                  A.2.3     Interworking
                  A.2.4     Special network nodes
                  A.2.5     Echo control logic
        A.3     SDL diagrams
Appendix I - Transmission of echo control information elements via signalling systems