Empfehlung der CCITT/ITU von 1993: Stage 3 description for number identification supplementary services using DSS 1 Clause 1 (02/92) Direct-dialling-in (DDI) Clause 2 (02/92) Multiple subscriber number (MSN) Clause 3 (1993) Calling line identification presentation Clause 4 (1993) Calling line identification restriction Clause 5 (1993) Connected line identification presentation Clause 6 (1993) Connected line identification restriction Clause 8 (02/92) Sub-addressing (SUB).