ÖNORM EN 300356-21 V 4.2.1:2001-11
Действует
Integrated Services Digital Network (ISDN) - Signalling System No.7 (SS7) - ISDN User Part (ISUP) version 4 for the international interface - Part 21: Anonymous Call Rejection (ACR) supplementary service [ITU-T Recommendation Q.731, clause 4 (1993)]
