ITU-T Rec. E.164 – NUMBERING PLAN FOR THE ISDN ERA
1 Introduction
2 Definitions
3 ISDN numbering plan principles
3.1 General
3.2 Structure of the international ISDN number
3.3 Number length
3.4 Number analysis
4 Number allocation principles
5 Network identification
6 Service identification
7 Calling/called line identity6)
8 Dialling procedures
9 Prefixes
10 Escape code
11 Address information
11.1 Direct dialling-in
11.2 Sub-addressing (network address extension)
11.3 Combination of sub-addressing and direct dialling-in
11.4 Address delimiters