CONTENTS

 1     Scope 
 2     References
        2.1     Normative references     
        2.2     Informative 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.2     Abstract model  
        A.3     SDL diagrams    
Appendix I – Transmission of echo control information elements via signalling systems