ETSI ETS 300 052-1991 Integrated Services Digital Network (ISDN); Multiple Subscriber Number (MSN) Supplementary Service Digital Subscriber Signalling System No. One (DSS1) Protocol
1994ETSI ETS 300 052-1994 Integrated Services Digital Network (ISDN); Multiple Subscriber Number (MSN) Supplementary Service Digital Subscriber Signalling System No. One (DSS1) Protocol
1991ETSI ETS 300 052-1991 Integrated Services Digital Network (ISDN); Multiple Subscriber Number (MSN) Supplementary Service Digital Subscriber Signalling System No. One (DSS1) Protocol