Overview
ISO/IEC 14845:1996 defines the Call Intrusion supplementary service (SS‑CI) for Private Integrated Services Networks (PISN). The standard provides both stage 1 (service definition as seen by users) and stage 2 (functional model and information flows) specifications. SS‑CI enables a served user to establish communication with a busy called user by breaking into an existing call, with options for forced release, isolation (conference vs. disconnecting the third party), and wait‑on‑busy behavior.
Keywords: ISO/IEC 14845:1996, Call Intrusion, SS-CI, PISN, supplementary service, CICL, CIPL, ISDN, functional model, information flows.
Key topics and technical requirements
- Service semantics (stage 1):
- Definition of Call Intrusion and related states (impending intrusion, intrusion state, wait on busy).
- Invocation modes: immediate invocation, consultation.
- Implementation options: forced release, isolation, wait on busy.
- Security / protection model:
- Call Intrusion Capability Level (CICL) - served user capability range 1–3.
- Call Intrusion Protection Level (CIPL) - protection levels 0–3 for users and gateways; intrusion allowed only if CICL > CIPL of both involved parties.
- Provisioning and scope:
- SS‑CI provisioned per PISN number and may be enabled per basic service (basic services defined in ISO/IEC 11574).
- Prearrangement with service provider required for provision/withdrawal.
- Stage 2 functional specification:
- Functional entities (FE1–FE5) and their actions/behaviors are defined.
- Information flows, mapping to basic call flows, and examples of sequences are included.
- Allocation of functional entities to physical equipment and SDL diagrams are provided.
- Conformance:
- A stage 3 standard (signalling protocols and equipment behaviour) is required to claim full conformance.
Applications and who uses it
- Telecommunication equipment vendors implementing enterprise PBX / PISN features.
- Network architects and designers defining call control and supplementary services for ISDN/PISN deployments.
- Protocol and firmware developers mapping functional models into signalling (stage 3) and equipment behaviour.
- Service providers offering managed PBX or enterprise telephony services that require controlled call override/priority access (e.g., administrative override, emergency coordination) while respecting protection levels.
Related standards
- ISO/IEC 11574 (basic call services)
- ISO/IEC 11579-1 (PISN exchange reference configuration)
- ISO/IEC 11571 (numbering/sub‑addressing)
- ISO/IEC 13864 / 13865 / 13866 / 13872 / 14136 / 14841 / 14842 (related PISN supplementary services and features)
- CCITT Recommendations I.112, I.130, I.221 (service description framework)
This standard is essential when designing or documenting PISN call control features where controlled intrusion into busy calls is required and must be interoperable and auditable across equipment and networks.
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