CONTENTS

 1     Scope 
 2     References 
 3     Definitions  
 4     Abbreviations   
 5     Overview of this Recommendation           
 6     Description of signals and messages         
        6.1     Escape Signal (ES)
        6.2     Mode Request (MR)         
        6.3     Capabilities Request (CR)  
        6.4     Mode Select (MS)
        6.5     Capabilities List (CL)         
        6.6     Capabilities List Request (CLR)     
        6.7     Acknowledge Message (ACK)      
        6.8     Negative Acknowledge Message (NAK)   
 7     Structure of signals and messages 
        7.1     Signals    
        7.2     Messages  
 8     Information field coding format     
        8.1     General  
        8.2     Coding format for parameters in the I and S fields   
        8.3     Identification field (I)          
        8.4     Standard information field (S)         
        8.5     Non-standard information field (NS)          
        8.6     Information field length       
 9     V.8 bis transactions         
        9.1     Permitted V.8 bis transactions        
        9.2     Transactions permitted at any time on the GSTN and on leased point-to-point circuits         
        9.3     Transactions permitted only upon automatic answering of a GSTN call        
        9.4     Use of escape signals         
        9.5     Use of the negative acknowledge message (NAK) 
        9.6     State transition diagrams    
        9.7     Suppression of ACK(1) after an MS message        
        9.8     Error recovery       
        9.9     Procedures for initiating a modem start-up after a V.8 bis transaction          
       9.10     Message segmentation      
10     Operating procedures     
       10.1     Operating procedures when not automatically answering on the GSTN and on leased point‑to‑point circuits    
       10.2     Operating procedures upon automatic answering of a call on the GSTN     
11     DTE-DCE interface        
Appendix I – Recommendation V.8 bis features    
        I.1     Introduction
        I.2     Basic features of this Recommendation        
        I.3     Selection of a desired communication mode
        I.4     Identification of common operating modes   
        I.5     Automatic selection between terminals        
        I.6     User-friendly switching from telephony to data        
        l.7     Conferencing applications    
        I.8     Interworking considerations
        I.9     Relationship between Recommendations V.8 and V.8 bis    
Appendix II – Examples of V.8 bis transactions    
Appendix III – Effect of echo suppressors    
      III.1     Introduction           
      III.2     Operation of echo suppressors       
      III.3     Dual tone signal breakthrough of echo suppressors 
      III.4     V.8 bis transactions 4, 5 and 6       
      III.5     Automatic answering together with a voice recording device
      III.6     Optional status of provisions