– ISO/IEC 11572:1997, Information technology – Telecommunications and information exchange between systems – Private Integrated Services Network – Circuit mode bearer services – Inter-exchange signalling procedures and protocol.
– ISO/IEC 11571:1994, Information technology – Telecommunications and information exchange between systems – Numbering and sub-addressing in private integrated services networks.
– ISO/IEC 15056:1997, Information technology – Telecommunications and information exchange between systems – Private Integrated Services Network – Inter-exchange signalling protocol – Transit counter additional network feature.