Integrated Services Digital Network (ISDN); CCITT signalling system No. 7; transaction capabilities application part (TCAP) version 2; English version ETS 300287:1993
Integrated Services Digital Network (ISDN) - Signalling System No. 7; ISDN User Part (ISUP) version 2 for the international interface - Part 1: Basic services [ITU-T Recommendations Q.761 to Q.764 (1993), modified]; English version ETS 300356-1:1995
Integrated Services Digital Network (ISDN) - Digital Subscriber Signalling System No. one (DSS1) protocol - Signalling network layer for circuit-mode basic call control - Part 1: Protocol specification [ITU-T Q.931 (1993), modified]; English version ETS 300403-1:1995