A part of the ISDN number, which is significant to the user, is passed to the user. This supplementary service is based on the use of the ISDN number and does not include sub-addressing.
ITU-T Q.81.1 FRENCH-1988 history
1988ITU-T Q.81.1 FRENCH-1988 Stage 2 Description for Number Identification Supplementary Services - Direct Dialling-in