Preface
1
Scope
2
DTE/DCE physical interface
elements
3
Alignment of call control
characters and error checking
4
Elements of the call control phase
for circuit switched service
5
Data transfer phase
6
Clearing phase
7
Test loops
Annex A – Interface signalling state diagrams
Annex B – Interface
signalling sequence diagrams and time-out operations
Annex C – DTE time-limits
and DCE time-outs
Annex D – Formats of
selection, call progress and DCE-provided information signals
Annex E – Interworking
between DTEs conforming to Recommendations X.21 and X.21 bis
Annex F – Coding of call
progress signals and DTE provided information
Annex G – Facility request,
indicator and parameter coding
Annex H – Information
content of DCE-provided information
Annex I – Reference
and transition tables