ETSI ETS 300 425 ed.1 (1995-09)

SLOVENSKI STANDARD
01-maj-2005
Zasebno telekomunikacijsko omrežje (PTN) – Specifikacija, funkcijski model in
informacijski pretoki - Dopolnilna storitev: vpad v klic
Private Telecommunication Network (PTN); Specification, functional models and
information flows; Call intrusion supplementary service
Ta slovenski standard je istoveten z: ETS 300 425 Edition 1
ICS:
33.040.35 Telefonska omrežja Telephone networks
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 425
TELECOMMUNICATION September 1995
STANDARD
Source: ETSI TC-ECMA Reference: DE/ECMA-00010
ICS: 33.040.10, 33.040.30
PTN, supplementary service
Key words:
Private Telecommunication Network (PTN);
Specification, functional model and information flows
Call intrusion supplementary service
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - secretariat@etsi.fr
X.400: Internet:
Tel.: +33 92 94 42 00 - Fax: +33 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1995. All rights reserved.
New presentation - see History box

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ETS 300 425: September 1995
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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Contents
Foreword .7
1 Scope .9
2 Conformance.9
3 References.9
4 Definitions.10
4.1 External definitions.10
4.2 Busy .11
4.3 Conference type connection .11
4.4 Consultation.11
4.5 Consultation timer.11
4.6 Established call.11
4.7 Forced release.11
4.8 Immediate invocation.11
4.9 Impending intrusion state.12
4.10 Impending intrusion warning notification.12
4.11 Implementation option .12
4.12 Intruding call.12
4.13 Intrusion state .12
4.14 Intruding call connected notification.12
4.15 Isolation.12
4.16 Path retention.12
4.17 Served user.12
4.18 Time to intrusion .12
4.19 User B.12
4.20 User C.12
4.21 WOB state .12
5 List of acronyms .13
6 SS-CI stage 1 specification .14
6.1 Description.14
6.1.1 General description .14
6.1.2 Qualifications on applicability to telecommunication services.14
6.2 Procedures.14
6.2.1 Provision and withdrawal.14
6.2.2 Normal procedures.15
6.2.2.1 Activation, deactivation, interrogation and registration .15
6.2.2.2 Invocation and operation .15
6.2.2.2.1 Methods of invoking SS-CI .15
6.2.2.2.2 Verification and selection of
compatible call .15
6.2.2.2.3 Actions during impending intrusion
state .16
6.2.2.2.3.1 Impending intrusion state ends.16
6.2.2.2.3.2 Release of intruding call .16
6.2.2.2.3.3 Release of established call.16
6.2.2.2.4 Setting up the connection between
served user, user B and user C.16
6.2.2.2.5 Actions during intrusion state.17
6.2.2.2.5.1 Release of intruding call.17
6.2.2.2.5.2 Release of the established call .17
6.2.2.2.5.3 Forced release.17
6.2.2.2.5.4 Isolation on request from served user .17

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6.2.2.2.5.5 Transition from intrusion state to WOB
state. 17
6.2.2.2.6 Actions during WOB state. 17
6.2.2.2.6.1 Served user releases . 17
6.2.2.2.6.2 User B answers the waiting call . 18
6.2.2.2.6.3 Re-intrusion request. 18
6.2.2.2.6.4 User B becomes not busy . 18
6.2.3 Exceptional procedures . 18
6.2.3.1 Activation, deactivation, registration and interrogation. 18
6.2.3.2 Invocation and operation. 18
6.3 Interactions with other supplementary services and ANFs . 18
6.3.1 Call Completion to Busy Subscriber (CCBS). 19
6.3.2 Call Completion No Reply (CCNR). 19
6.3.3 Do Not Disturb (DND). 19
6.3.4 Do Not Disturb Override (DNDO) . 19
6.3.5 Calling Line Identification Presentation (CLIP) . 19
6.3.6 Calling/Connected Line Identification Restriction (CLIR). 19
6.3.7 Connected Line Identification Presentation (COLP). 19
6.3.8 Calling Name Identification Presentation (CNIP). 19
6.3.9 Connected Name Identification Presentation (CONP) . 20
6.3.10 Calling/Connected Name Identification Restriction (CNIR) . 20
6.3.11 Call Forwarding Unconditional (CFU) . 20
6.3.12 Call Forwarding No Reply (CFNR). 20
6.3.13 Call Forwarding Busy (CFB) . 20
6.3.14 Call Transfer (CT). 20
6.3.15 Path Replacement (ANF-PR) . 21
6.3.16 Call Offer (CO). 21
6.4 Interworking considerations . 21
6.5 Overall SDL. 21
7 SS-CI stage 2 specification. 30
7.1 Functional model. 30
7.1.1 Functional model description. 30
7.1.2 Description of the Functional Entities . 31
7.1.2.1 SS-CI requesting entity, FE1. 31
7.1.2.2 Served user's service control entity, FE2. 31
7.1.2.3 Intrusion service control entity and user B's control entity,
FE3. 32
7.1.2.4 User C's control entity, FE4 . 32
7.1.2.5 User C agent, FE5 . 32
7.1.3 Relationship of functional model to basic call functional model. 33
7.2 Information flows . 33
7.2.1 Definition of information flows. 33
7.2.1.1 Relationship ra . 33
7.2.1.1.1 INFORM . 33
7.2.1.1.2 CI_INV. 33
7.2.1.1.3 WARNING. 34
7.2.1.1.4 ISOLATE . 34
7.2.1.1.5 FORCE_REL. 34
7.2.1.1.6 EST_TERM . 34
7.2.1.1.7 REQUEST_WOB . 35
7.2.1.1.8 B_ALERTING. 35
7.2.1.1.9 B_ANSWER. 35
7.2.1.2 Relationship rb . 35
7.2.1.2.1 CI_ACT . 35
7.2.1.2.2 ISOLATE . 36
7.2.1.2.3 WARNING. 36
7.2.1.2.4 FORCE_REL. 36
7.2.1.2.5 EST_TERM . 36
7.2.1.2.6 REQUEST_WOB . 37
7.2.1.2.7 CI_AVAIL. 37
7.2.1.2.8 CI_INV. 37
7.2.1.2.9 B_ALERTING. 38
7.2.1.2.10 B_ANSWER. 38

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7.2.1.3 Relationship rc.38
7.2.1.3.1 INFO_REQ .38
7.2.1.3.2 WARNING .38
7.2.1.3.3 C_INTR.38
7.2.1.3.4 C_ISOLATED .38
7.2.1.3.5 C_FORCED_REL .38
7.2.1.3.6 INTR_TERM .38
7.2.1.4 Relationship rd.39
7.2.1.4.1 WARNING .39
7.2.1.4.2 C_INTR.39
7.2.1.4.3 C_ISOLATED .39
7.2.1.4.4 C_FORCED_REL .39
7.2.1.4.5 INTR_TERM .39
7.2.2 Relationship of information flows to basic call information flows.40
7.2.2.1 Information flows over ra .40
7.2.2.2 Information flows over rb .41
7.2.2.3 Information flows over rc .42
7.2.2.4 Information flows over rd .42
7.2.2.5 Summary .42
7.2.3 Information flow sequences .44
7.2.3.1 Normal operation, consultation, path retention.44
7.2.3.2 Normal operation, consultation, non-retention.45
7.2.3.3 Normal operation, immediate invocation, non-retention.46
7.2.3.4 Normal operation, immediate invocation, path retention .47
7.2.3.5 Normal operation, immediate invocation, path retention,
user C isolated at intrusion .48
7.2.3.6 Normal operation, immediate invocation, immediate
intrusion, non-retention.49
7.2.3.7 Normal operation, immediate invocation, path retention .50
7.2.3.8 Normal operation, isolation of user C .51
7.2.3.9 Normal operation, Forced Release of user C.51
7.2.3.10 Normal operation, user B or user C releases the
established call .52
7.2.3.11 Normal operation, release of the intruding call .52
7.2.3.12 Normal operation, WOB requested .53
7.2.3.13 Normal operation, new intrusion during WOB .54
7.3 Functional Entity actions (FEAs).54
7.3.1 Actions of FE1.54
7.3.2 Actions of FE2.55
7.3.3 Actions of FE3.56
7.3.4 Actions of FE4.58
7.3.5 Actions of FE5.58
7.4 Functional Entity behaviour.58
7.4.1 Behaviour of FE1.58
7.4.2 Behaviour of FE2.67
7.4.3 Behaviour of FE3.77
7.4.4 Behaviour of FE4.85
7.4.5 Behaviour of FE5.86
7.5 Allocation of Functional Entities to physical equipment .87
7.6 Interworking considerations .87
History.89

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Foreword
This European Telecommunication Standard (ETS) has been produced by the European Computer
Manufacturers Association (ECMA) on behalf of its members and those of the European
Telecommunications Standards Institute (ETSI).
This ETS is one of a series of standards defining services and signalling protocols applicable to
Private Telecommunication Networks (PTNs). The series uses the ISDN concepts as developed by
the ITU-T (formerly CCITT) and is also within the framework of standards for open systems
interconnection as defined by ISO.
This ETS specifies the Call Intrusion supplementary service.
The ETS is based upon the practical experience of ECMA member companies and the results of
their active and continuous participation in the work of ISO, ITU-T, ETSI and other international and
national standardization bodies. It represents a pragmatic and widely based consensus.
This ETS was produced by ECMA using the ECMA guidelines for the production of standards and
using the ECMA stylesheet. In order to avoid undue delays in the approval process for this ETS it
has been agreed that this ETS will not be converted to the ETSI stylesheet.

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1 Scope
This European Telecommunication Standard (ETS) specifies the Call Intrusion
supplementary service (SS-CI), which is applicable to basic services supported by Private
Telecommunication Networks (PTNs). Basic services are specified in ETS 300 171.
Call Intrusion (SS-CI) is a supplementary service which, on request from the served user,
enables the served user to establish communication with a busy called user (user B) by
breaking into an established call between user B and a third user (user C).
Service specifications are produced in three stages, according to the method described in
ETS 300 387. This ETS contains the stage 1 and stage 2 specifications of SS-CI. The stage
1 specification (clause 6) specifies the supplementary service as seen by users of PTNs. The
stage 2 specification (clause 7) identifies the Functional Entities involved in the
supplementary service and the information flows between them.
The purpose of the stage 1 and stage 2 specifications is to guide and constrain the work on
signalling protocols at stage 3. Stage 3, the definition of the network and access layer 3
signalling protocols to support the supplementary service, is defined in separate standards.
NOTE 1
For this ETS, stage 2 does not consider the split of functionality between a functional TE at user B
and the local PTNX. TE functions and local PTNX functions at user B are included in the same
Functional Entity.
2 Conformance
In order to conform to this ETS, a stage 3 standard shall specify signalling protocols and
equipment behaviour that are capable of being used in a PTN which supports the
supplementary service specified in this ETS. This means that, to claim conformance, a stage
3 standard is required to be adequate for the support of those aspects of clause 6 (stage 1)
and clause 7 (stage 2) which are relevant to the interface or equipment to which the stage 3
standard applies.
3 References
ETS 300 171 Private Telecommunication Network (PTN); Specification,
functional models and information flows; Control aspects of
circuit mode basic services (1992)
ETS 300 173 Private Telecommunication Network (PTN); Specification,
functional models and information flows; Identification
supplementary services (ISSD) (1992)
ETS 300 189 Private Telecommunication Network (PTN); Addressing (1992)
ETS 300 237 Private Telecommunication Network (PTN); Specification,
functional models and information flows; Name identification
supplementary services (1993)
ETS 300 256 Private Telecommunication Network (PTN); Specification,
functional models and information flows; Diversion
supplementary services (1993)
ETS 300 258 Private Telecommunication Network (PTN); Specification,
functional models and information flows; Path replacement
additional network feature (1993)
ETS 300 260 Private Telecommunication Network (PTN); Specification,
functional models and information flows; Call transfer
supplementary service (1993)
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ETS 300 361 Private Telecommunication Network (PTN); Specification,
functional model and information flows; Call offer supplementary
service (1994)
ETS 300 363 Private Telecommunication Network (PTN); Specification,
functional model and information flows; Do not disturb and do
not disturb override supplementary services (1994)
ETS 300 365 Private Telecommunication Network (PTN); Specification,
functional model and information flows; Call completion
supplementary services (1994)
ETS 300 387 Private Telecommunications Network (PTN); Method for the
specification of basic and supplementary services (1994)
ETS 300 415 Private Telecommunication Network (PTN); Terms and
definitions (1995)
CCITT Recommendation I.112 Vocabulary of terms for ISDNs (1988)
CCITT Recommendation I.210 Principles of telecommunication services supported by an
ISDN
and the means to describe them (1988)
CCITT Recommendation I.221 Common specific characteristics of services (1988)
CCITT Recommendation Z.100 Specification and Description Language (SDL) (1988)
4 Definitions
For the purpose of this ETS the following definitions apply:
4.1 External definitions
This ETS uses the following terms defined in other documents:
− Basic Service (CCITT Rec. I.210)
− Calling Party Name ETS 300 237
− Connection (CCITT Rec. I.112)
− Integrated Services Digital Network (CCITT Rec. I.112)
− Name ETS 300 237
− Network Determined User Busy (CCITT Rec. I.221)
− Number ETS 300 189
− Private Telecommunication Network Exchange (PTNX) (ETS 300 415)
− Public (ETS 300 415)
− Service (CCITT Rec. I.112)
− Signalling (CCITT Rec. I.112)
− Subaddress ETS 300 189
− Supplementary Service (CCITT Rec. I.210)
− Private Telecommunication Network (ETS 300 415)
− Terminal Equipment (ETS 300 415)
− User (ETS 300 171)
− User Determined User Busy (CCITT Rec. I.221)

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This ETS refers to the following basic call Functional Entities (FEs) defined in
ETS 300 171:
− Call Control (CC)
− Call Control Agent (CCA)
This ETS refers to the following basic call inter-FE relationships defined in ETS 300 171:
− r1
− r2
− r3
This ETS refers to the following basic call information flows defined in ETS 300 171:
− DISCONNECT request/indication
− RELEASE request/indication
− RELEASE response/confirmation
− SETUP request/indication
− SETUP response/confirmation
This ETS refers to the following basic call information flow elements defined in
ETS 300 171:
− Destination number
− Connection type
This ETS refers to the following information flow elements defined in ETS 300 173:
− Originating number
− Originating subaddress
4.2 Busy
A property of a user for whom either a Network Determined User Busy or User Determined
User Busy condition exists.
4.3 Conference type connection
A connection between the served user, user B and user C, where all users have user
information connection with each other.
4.4 Consultation
Invocation of SS-CI after the calling user has been informed that a call has failed because
of busy at the destination.
4.5 Consultation timer
A timer governing the time in which the calling user is allowed to request invocation of SS-
CI after being informed that a call has failed because of busy at the destination. The
duration of the timer is an implementation option.
4.6 Established call
The active call that is selected for intruding on.
4.7 Forced release
The release of the established call on request from the served user during the intrusion
state.
4.8 Immediate invocation
Invocation of SS-CI as part of the initial call set up.

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4.9 Impending intrusion state
The condition of an established call and an intruding call after provision of an impending
intrusion warning notification and before establishment of communication between the
served user and user B.
4.10 Impending intrusion warning notification
A notification provided before communication is established between the served user and
user B.
4.11 Implementation option
An option for the implementor of the service to include or not to include in the service
providing system.
4.12 Intruding call
A call in which the served user requests SS-CI.
4.13 Intrusion state
The condition of an established call after establishment of communication between the
served user and user B and prior to termination of SS-CI or invocation of Wait On Busy
(WOB).
4.14 Intruding call connected notification
A notification provided on establishment of communication between the served user and
user B.
4.15 Isolation
The breaking of the user information connection to and from user C during the intrusion
state.
4.16 Path retention
The retaining of the network connection between the originating CC and the destination CC
so that a supplementary service (such as SS-CI) can be invoked without establishing a
new connection.
4.17 Served user
The user who requests SS-CI.
4.18 Time to intrusion
The duration of the impending intrusion state.
4.19 User B
The wanted user that is subject to the call intrusion.
4.20 User C
The other user in the established call.
4.21 WOB state
A state that can be entered from the intrusion state and in which the intruding call is
disconnected from user B and is waiting for user B to answer the call.

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5 List of acronyms
ANF Additional Network Feature
CC Call Control (Functional Entity)
CCA Call Control Agent (Functional Entity)
CCBS Call Completion to Busy Subscriber
CCNR Call Completion No Reply
CFB Call Forwarding Busy
CFNR Call Forwarding No Reply
CFU Call Forwarding Unconditional
CI Call Intrusion
CICL Call Intrusion Capability Level
CIPL Call Intrusion Protection Level
CLIP Calling Line Identification Presentation
CLIR Calling/Connected Line Identification Restriction
CNIP Calling Name Identification Presentation
CNIR Calling/Connected Name Identification Restriction
CO Call Offer
COLP Connected Line Identification Presentation
CONP Connected Name Identification Presentation
CT Call Transfer
DND Do Not Disturb
DNDO Do Not Disturb Override
FE Functional Entity
ISDN Integrated Services Digital Network
NDUB Network Determined User Busy
PTN Private Telecommunication Network
PTNX Private Telecommunication Network Exchange
SDL Specification and Description Language
SS Supplementary Service
TE Terminal Equipment
UDUB User Determined User Busy
WOB Wait On Busy
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6 SS-CI stage 1 specification
6.1 Description
6.1.1 General description
Call Intrusion (SS-CI) is a supplementary service which, on request from the served
user, enables the served user to establish communication with a busy called user (user
B) by breaking into an established call between user B and a third user (user C). On
successful intrusion, user C is either connected in a conference type connection with the
served user and user B or disconnected from user B (isolated).
An intrusion request is only accepted if the served user has a higher Call Intrusion
Capability Level (CICL) than the Call Intrusion Protection Level (CIPL) of both user B
and user C.
There are three implementation options that provide the served user with additional
capabilities following successful intrusion:
• Forced release, allowing the served user to release the established call;
• Isolation, allowing the served user, if a conference type connection has been
established, to isolate user C;
• WOB, allowing the served user to cause a transition from the intrusion state to the
WOB state.
6.1.2 Qualifications on applicability to telecommunication services
SS-CI is applicable to all circuit mode basic telecommunication services defined in
ETS 300 171 where considered meaningful.
6.2 Procedures
6.2.1 Provision and withdrawal
SS-CI shall be provided or withdrawn after pre-arrangement with the service provider.
SS-CI shall be provided on a per PTN number basis. For each PTN number, the
supplementary service may be provided for those basic services for which it is
considered meaningful (see 6.1.2) provided at that PTN number or for only some of
these basic services provided at that PTN number.
A Call Intrusion Capability Level (CICL) shall be allocated to the served user. Call
Intrusion Protection Levels (CIPLs) shall be allocated to potential individual users B and
C within the PTN and to gateways to other networks (for use on behalf of users outside
the PTN). The procedure by which CICL and CIPL are allocated is outside the scope of
this ETS.
CICL shall have a value in the range 1 (lowest capability) to 3 (highest capability). At
least one of the CICL values shall be offered.
CIPL shall have a value in the range 0 (no protection) to 3 (total protection). CIPL values
0 and 3 shall be offered, and values 1 and 2 may, as an implementation option, be
offered.
NOTE 2
It is not precluded that CIPL values can be variable, e.g. a user may have the possibility to
change the CIPL value with a user procedure. CIPL values assigned to gateways may also
be variable, e.g. depending on whether the gateway is used for an incoming or outgoing call
to the PTN. The details of such capabilities are outside the scope of this ETS.

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At least one of the methods of invoking SS-CI (see 6.2.2.2.1) shall be supported. If both
methods given in 6.2.2.2.1 are supported, then a user may be provided with one or both
methods.
A number of implementation options concern features available to the served user
during call intrusion. The served user may, at time of provision of SS-CI, be given the
choice of being provided with some, all or none of these or the options may be generally
available. These implementation options are: forced release, isolation, and WOB.
When these options are selectable on a per served user basis, they may be selectable
separately for each basic service for which SS-CI is provided, or selectable only for all
basic services for which SS-CI is provided.
6.2.2 Normal procedures
6.2.2.1 Activation, deactivation, interrogation and registration
SS-CI shall be activated by the service provider upon provision, and deactivated upon
withdrawal.
Registration and interrogation shall not apply.
6.2.2.2 Invocation and operation
6.2.2.2.1 Methods of invoking SS-CI
There are two different ways to invoke SS-CI. A PTN shall offer one or both of
these ways. These ways are:
a) Consultation: the served user, on being informed that a call has failed
because of busy at the destination, shall be able, within a defined period
(consultation timer), to request SS-CI.
b) Immediate invocation: the served user shall be able to request SS-CI as part
of the initial call set up.
6.2.2.2.2 Verification and selection of compatible call
If the consultation method is provided to the served user, the following procedure
shall apply. If a call fails due to busy at the called user B and the PTN is not aware
that intrusion is not allowed (e.g. because of insufficient CICL), the PTN shall notify
the served user that the call has failed because of busy at the called user B and
that intrusion may be possible. The served user may then request SS-CI.
If the immediate invocation method is provided to the served user, the served user
may request SS-CI with the initial call set up.
For both invocation alternatives the following shall apply. Upon receiving an
intrusion invocation request from the served user, the PTN shall check that the user
B's number used by the served user, when requesting the service, is also a number
involved in a compatible call in the active state. A called user's subaddress supplied
by the served user shall not be taken into account when selecting a call to intrude
on. Further, the PTN checks that the CIPL values of the users in the active call are
lower than the CICL value of the served user. If user B's CIPL value is lower than
the CICL value and user B has several compatible calls in the active state, the CIPL
values of the other users in the calls shall be checked, in any order, until a CIPL
value lower than the CICL value is found. A call that passes these checks shall be
selected as the established call.
When the established call has been selected, the users in the established call may
as an option be provided an Impending intrusion warning notification and short
delay before the connection between the served user and user B is formed. If this

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notification is provided, it shall be sent to both users in the established call and
optionally to the served user and the impending intrusion state shall be entered.
NOTE 3
The Impending intrusion warning notification can be accompanied by an in-band tone or
announcement to user B and user C. An in-band tone or announcement can be given to
the served user.
If no Impending intrusion warning notification is provided, the procedures of
6.2.2.2.4 for setting up the connection between the served user and user B shall
apply immediately.
6.2.2.2.3 Actions during impending intrusion state
6.2.2.2.3.1 Impending intrusion state ends
A time period, time to intrusion (1-10 seconds, implementation option), after the
Impending intrusion warning notification has been provided the impending
intrusion state shall be terminated and the procedures of 6.2.2.2.4 for setting up
the connection between the served user and user B shall apply.
6.2.2.2.3.2 Release of intruding call
If the served user releases the intruding call during the impending intrusion state,
user B and user C shall each be notified that intrusion has terminated. SS-CI
shall be terminated.
6.2.2.2.3.3 Release of established call
If user B or user C releases the established call, the served user shall be notified
that intrusion is no longer applicable. SS-CI shall be terminated and the network
shall attempt to present the call from the served user to user B and continue in
accordance with basic call procedure.
6.2.2.2.4 Setting up the connection between served user, user B and user C
There are two different ways (implementation options) for the served user to be
connected to user B. Either the network shall form a conference type connection
between user B, user C and the served user, or the network shall isolate user C
and connect the served user only to user B. In either case, when the connection
has been established, the intrusion state shall be entered.
If the first option is implemented, the users in the established call shall be provided
with an Intruding call connected notification when the served user is connected.
The served user shall receive confirmation that the intrusion request has been
accepted and that a conference type connection has been formed.
NOTE 4
The three users can also receive a superimposed in-band indication (e.g. a repeated
tone) while the conference type connection exists.
If the latter option is implemented, user C shall be given a notification that isolation
has occurred and user B shall be informed that user C has been isolated and that
an intrusion has occurred. The served user shall receive confirmation that the
intrusion request has been accepted and that isolation has occurred. The served
user and user B shall be connected and no conference type connection shall be
formed. The established call shall remain in progress but with the user information
connection to user C broken.
NOTE 5
User C can also receive an in-band tone or announcement while isolated.

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6.2.2.2.5 Actions during intrusion state
6.2.2.2.5.1 Release of intruding call
If the served user releases the intruding call, the established call shall revert to
the state that existed before the intrusion state, and the intrusion state shall be
terminated. User B and user C shall be notified that the intrusion state has been
terminated.
If user B releases the intruding call, the established call shall revert to the state
that existed before the intrusion state, and the intrusion state shall be terminated.
User C shall be notified that the intrusion state has terminated.
6.2.2.2.5.2 Release of the established call
If user B or user C releases the established call, the served user shall be notified
that call intrusion has terminated. If user C releases the established call, user B
shall be notified that intrusion has terminated. The intruding call shall become an
ordinary call between user B and the served user.
6.2.2.2.5.3 Forced release
As an implementation option the served user may, during the intrusion state,
request a forced release of user C. User C may be isolated or in a conference
type connection when the request is made. A successful forced release shall be
notified to the served user, to user B and to user C. The intruding call shall
continue as an ordinary call between the served user and user B, the established
call shall be released, and the intrusion state shall be terminated.
6.2.2.2.5.4 Isolation on request from served user
If a conference type connection is used, user C may (implementation option) be
isolated from the conference type connection on request from the served user. If
the request is accepted the served user shall receive confirmation and the
established call shall be disconnected from user B, but not released. The served
user shall be connected only to user B. The intrusion state shall continue and the
ensuing situation shall be identical to the situation where isolation occurred when
the intrusion state was entered. User C and user B shall be notified that user C
has been isolated.
6.2.2.2.5.5 Transition from intrusion state to WOB state
As an implementation option it may be possible for the served user to request
transition from the intrusion state to the WOB state. On acceptance of such a
request, the served user shall receive a confirmation, the established call shall
revert back to the state that existed before intrusion, user B shall be reconnected
to user C if isolated, the intruding call shall be disconnected from user B and the
intrusion state shall be terminated. The intruding call shall not be released but
shall enter the WOB state. User B shall be notified that the intrusion has
terminated and WOB has been invoked. User C shall be notified that the
intrusion has terminated.
6.2.2.2.6 Actions during WOB state
6.2.2.2.6.1 Served user releases
If the served user releases during the WOB state, user B shall be notified and
SS-CI terminated.
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6.2.2.2.6.2 User B answers the waiting call
If user B answers the waiting call, SS-CI shall be terminated, and the served user
shall be notified and connected to user B. The call shall become an ordinary call
between user B and the served user.
6.2.2.2.6.3 Re-intrusion request
When the network receives a request for re-intrusion, the network shall verify the
request and select an established call in accordance with 6.2.2.2.2 and set up
the connection in accordance with 6.2.2.2.3 (if applicable) and 6.2.2.2.4.
6.2.2.2.6.4 User B becomes not busy
If the PTN detects that the necessary resources have become available, it shall
transfer an incoming call indication to user B. If user B starts alerting, the served
user shall receive an appropriate indication.
6.2.3 Exceptional procedures
6.2.3.1 Activation, deactivation, registration and interrogation
Not applicable.
6.2.3.2 Invocation and operation
If the served user requests invocation of SS-CI as part of the initial call request, and
immediate invocation is not provided to the served user, then the request shall be
ignored and the call shall proceed as if the request had not been made.
If a SS-CI or re-intrusion request is rejected, the served user shall be informed, and
may be given an indication of the reason for the rejection. Possible reasons to reject a
SS-CI or re-intrusion request are e.g.:
− served user has a lower or equal CICL compared with user B's and/or user C's
CIPL value;
− user B is busy but not involved in a compatible call in the active state;
− temporary lack of resources;
− the established call is already being intruded upon;
− the established call is intruding on another call.
If SS-CI is requested and user B is found to be not busy, the call shall be treated as a
normal incoming call to user B.
If a forced release, isolate or WOB request from the served user is denied by the
PTN, the served user shall be notified and may be given an indication for the reason
of the denial. The intrusion state shall remain.
If an intrusion request from the WOB state is rejected, the WOB state shall remain.
If consultation applies to the call, the call shall be released either if the served user
does not request invocation within the defined time period (consultation timer) or if the
served user requests invocation within the defined time period (consultation timer)
and this request is rejected.
Consultation shall not apply if the called user is busy and the PTN is aware that
intrusion is not allowed. Basic call procedures shall apply.
6.3 Interactions with other supplementary services and ANFs
Interactions with other supplementary services and ANFs for which PTN standards were
available at the time of the publication of this ETS are specified below.

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6.3.1 Call Completion to Busy Subscriber (CCBS)
SS-CCBS requested by the served user while in the intrusion state shall be rejected.
While in the WOB state, the s
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