ISO/IEC 19460:2001

INTERNATIONAL ISO/IEC
STANDARD 19460
First edition
2001-05-01
Information technology —
Telecommunications and information
exchange between systems — Private
Integrated Services Network —
Inter-exchange signalling protocol —
Single Step Call Transfer Supplementary
Service
Technologies de l'information — Télécommunications et échange
d'information entre systèmes — Réseau privé à intégration de services —
Protocole de signalisation d'interchange — Service supplémentaire de
transfert d'appel à pas unique
Reference number
©
ISO/IEC 2001
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ii © ISO/IEC 2001 – All rights reserved

Contents Page
Foreword v
Introduction vi
1 Scope 1
2 Conformance 1
3 Normative references 1
4 Terms and definitions 2
4.1 External definitions 2
4.2 Other definitions 3
4.2.1 Rerouting number 3
4.2.2 Rerouting PINX 3
4.2.3 Transferred PINX 3
4.2.4 Transferred-To PINX 3
4.2.5 Transferring PINX 3
5 Acronyms 3
6 Signalling protocol for the support of SS-SSCT 4
6.1 SS-SSCT description 4
6.2 SS-SSCT operational requirements 4
6.2.1 Provision/Withdrawal 4
6.2.2 Requirements on a Transferring PINX 4
6.2.3 Requirements on a Rerouting PINX 4
6.2.4 Requirements on a Transferred PINX 4
6.2.5 Requirements on a Transferred-To PINX 4
6.2.6 Requirements on a Transit PINX 4
6.3 SS-SSCT coding requirements 5
6.3.1 Operations 5
6.3.2 Information elements 7
6.3.3 Messages 7
6.4 SS-SSCT state definitions 7
6.4.1 States at a Transferring PINX 7
6.4.2 States at a Rerouting PINX 7
6.4.3 States at a Transferred PINX 8
6.4.4 States at a Transferred-To PINX 8
6.5 SS-SSCT signalling procedures 8
6.5.1 Actions at a Transferring PINX 8
6.5.2 Procedures at the Rerouting PINX 9
6.5.3 Actions at a Transferred PINX 11
6.5.4 Actions at a Transferred-To PINX 11
6.5.5 Actions at a Transit PINX 11
6.5.6 Subsequent actions at Transferred and Transferred-To PINX 11
6.6 SS-SSCT impact of interworking with public ISDNs 11
6.6.1 Actions at a Gateway PINX 11
© ISO/IEC 2001 – All rights reserved iii

6.7 SS-SSCT impact of interworking with non-ISDNs 12
6.7.1 Actions at a Gateway PINX 12
6.8 Protocol Interactions between SS-SSCT and other supplementary services and ANFs 12
6.8.1 Calling Name Identification Presentation (SS-CNIP) 12
6.8.2 Connected Name Identification Presentation (SS-CONP) 12
6.8.3 Completion of Calls to Busy Subscribers (SS-CCBS) 12
6.8.4 Completion of Calls on No Reply (SS-CCNR) 12
6.8.5 CallForwarding Unconditional (SS-CFU) 12
6.8.6 Call Forwarding Busy (SS-CFB) 13
6.8.7 Call Forwarding No Reply (SS-CFNR) 13
6.8.8 Call Deflection (SS-CD) 13
6.8.9 Call Transfer (SS-CT) 13
6.8.10 Path Replacement (ANF-PR) 14
6.8.11 Advice Of Charge (SS-AOC) 14
6.8.12 Call Offer (SS-CO) 15
6.8.13 Do Not Disturb (SS-DND)15
6.8.14 Do Not Disturb Override (SS-DNDO) 15
6.8.15 Recall (SS-RE) 15
6.8.16 Call Intrusion (SS-CI) 15
6.8.17 Call Interception (ANF-CINT) 15
6.8.18 Transit Counter (SS-TC) 16
6.8.19 Route Restriction Class (ANF-RRC) 16
6.8.20 Authentication of the PISN (SS-WTAN) 16
6.8.21 Authentication of a WTM user (SS-WTAT) 16
6.8.22 Wireless Terminal Location Registration (SS-WTLR) 16
6.8.23 Wireless Terminal Mobility Incoming Call (ANF-WTMI) 16
6.8.24 Wireless Terminal Mobility Outgoing Call (ANF-WTMO) 16
6.8.25 Message Waiting Indication (SS-MWI) 16
6.8.26 User Mobility Incoming Call (ANF-PUMI) 16
6.8.27 User Mobility Outgoing Call (ANF-PUMO) 16
6.8.28 Private User Mobility - Registration (SS-PUMR) 16
6.8.29 CommonInformation(ANF-CMN) 16
6.8.30 Call Priority Interruption (Protection) (SS-CPI(P)) 17
6.9 SS-SSCT Parameter values (Timers) 17
6.9.1 Timer T1 17
6.9.2 Timer T2 17
6.9.3 Timer T3 17
Annexes
A- Protocol Implementation Conformance Statement (PICS) proforma 18
B- Imported ASN.1 definitions 26
C- Examples of message sequences 30
D- Specification and Description Language (SDL) representation of procedures 35
E- Additional feature identifier in module Common-Information-Operations 44
F- Difference between Single Step Call Transfer and Call Transfer by Rerouting 45
iv © ISO/IEC 2001 – All rights reserved

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the
specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the
development of International Standards through technical committees established by the respective organization to deal with
particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft
International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights.
ISO and IEC shall not be held responsible for identifying any or all such patent rights.
International Standard ISO/IEC 19460 was prepared by ECMA (as ECMA-300) and was adopted, under a special “fast-track
procedure”, by Joint Technical Committee ISO/IEC JTC 1, Information technology, in parallel with its approval by national
bodies of ISO and IEC.
Annexes A and E form a normative part of this International Standard. Annexes B, C, D and F are for information only.
© ISO/IEC 2001 – All rights reserved v

Introduction
This International Standard is one of a series of Standards defining services and signalling protocols applicable to Private
Integrated Services Networks (PISNs). The series uses ISDN concepts as developed by ITU-T and conforms to the framework
of International Standards for Open Systems Interconnection as defined by ISO/IEC.
This International Standard specifies the signalling protocol for use at the Q reference point in support of the Call Transfer
supplementary service. The protocol defined in this International Standard forms part of the PSS1 protocol (informally known
as QSIG).
This International Standard is based upon the practical experience of ECMA member companies and the results of their active
and continuous participation in the work of ISO/IEC JTC 1, ITU-T, ETSI and other international and national standardization
bodies. It represents a pragmatic and widely based consensus.
vi © ISO/IEC 2001 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 19460:2001(E)
Information technology — Telecommunications and information exchange between
systems — Private Integrated Services Network — Inter-exchange signalling
protocol — Single Step Call Transfer Supplementary Service
1Scope
This International Standard specifies the signalling protocol for the support of the Single Step Call Transfer Supplementary
Service (SS-SSCT) at the Q reference point between Private Integrated Network services eXchanges (PINXs) connected
together within a Private Integrated Services Network (PISN).
SS-SSCT is a supplementary service which enables a user, user A, to transform an existing call between user A and user B into
a new call between user B and a user C whereby user A does not have a call established with user C prior to call transfer.
The Q reference point is defined in ISO/IEC 11579-1.
Service specifications are produced in three stages and according to the method specified in ETS 300 387. This International
Standard contains the stage 3 specification for the Q reference point and satisfies the requirements identified by the stage 1 and
stage 2 specifications in ISO/IEC 19459.
The signalling protocol for SS-SSCT operates on top of the signalling protocol for basic circuit switched call control, as
specified in ISO/IEC 11572, and uses certain aspects of the generic procedures for the control of supplementary services
specified in ISO/IEC 11582.
This International Standard also specifies additional signalling protocol requirements for the support of interactions at the Q
reference point between Single Step Call Transfer and other supplementary services and ANFs.
This International Standard is applicable to PINXs which can interconnect to form a PISN.
2 Conformance
In order to conform to this International Standard, a PINX shall satisfy the requirements identified in the Protocol
Implementation Conformance Statement (PICS) proforma in annex A.
Conformance to this International Standard includes conforming to those clauses that specify protocol interactions between
SS-SSCT and other supplementary services and ANFs for which signalling protocols at the Q reference point are supported in
accordance with the stage 3 standards concerned.
3 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this
International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not
apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of
applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the
normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards.
ISO/IEC 11571:1998, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Networks - Addressing.
ISO/IEC 11572:2000, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network (PISN) - Circuit mode bearer services - Inter-exchange signalling procedures and protocol.
ISO/IEC 11574:2000, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Circuit-mode 64 kbit/s bearer services - Service description, functional capabilities and
information flows.
ISO/IEC 11579-1:1994, Information technology - Telecommunications and information exchange between systems - Private
integrated services network - Part 1: Reference configuration for PISN Exchanges (PINX).
© ISO/IEC 2001 – All rights reserved 1

ISO/IEC 11582:1995, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Generic functional protocol for the support of supplementary services - Inter-exchange
signalling procedures and protocol.
ISO/IEC 13868:1995, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Inter-exchange signalling protocol - Name identification supplementary services.
ISO/IEC 13869:1995, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Inter-exchange signalling protocol - Call transfer supplementary service.
ISO/IEC 13873:1995, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Inter-exchange signalling protocol - Call diversion supplementary services.
ISO/IEC 13874:1999, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Inter-exchange signalling protocol - Path replacement additional network feature.
ISO/IEC 15050:1997, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Inter-exchange signalling protocol - Advice of charge supplementary services.
ISO/IEC 15054:1997, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Inter-exchange signalling protocol - Call interception additional network feature.
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.
ISO/IEC 15772:1998, Information technology - Telecommunications and information exchange between system - Private
Integrated Services Network - Inter-exchange signalling protocol - Common information additional network.
ISO/IEC 15992:1998, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Inter-exchange signalling protocol - Call priority interruption and call priority interruption
protection supplementary services.
ISO/IEC 19459:2001, Information technology - Telecommunications and information exchange between systems - Private
Integrated Services Network - Specification, functional model and information flows - Single step call transfer supplementary
service.
ETS 300 387:1994, Private Telecommunication Network (PTN); Method for the specification of basic and supplementary
services.
ITU-T Rec. I.112:1993, Vocabulary of terms for ISDNs.
ITU-T Rec. I.210:1993, Principles of telecommunication services supported by an ISDN and the means to describe them.
ITU-T Rec. Q.950, Supplementary services protocols, structure and general principles.
ITU-T Rec. Z.100:1999, Specification and description language (SDL).
4 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
4.1 External definitions
This International Standard uses the following terms defined in other documents:
- Application Protocol Data Unit (APDU) (ISO/IEC 11582)
- Basic Service (ITU-T Rec. I.210)
- Gateway PINX (ISO/IEC 11572)
- Complete Number (ISO/IEC 11571)
- Interpretation APDU (ISO/IEC 11582)
- Network Facility Extension (NFE) (ISO/IEC 11582)
- New Call, New Connection (ISO/IEC 19459)
- Original Call, Original Connection (ISO/IEC 19459)
- Originating PINX (ISO/IEC 11582)
- Private Integrated Services Network (PISN) (ISO/IEC 11579-1)
© ISO/IEC 2001 – All rights reserved
- Private Integrated services Network eXchange (PINX) (ISO/IEC 11579-1)
- Subsequent PINX (ISO/IEC 11582)
- Signalling (ITU-T Rec. I.112)
- Supplementary Service (ITU-T Rec. I.210)
- Supplementary Service Control Entity (ISO/IEC 11582)
- Terminating PINX (ISO/IEC 11582)
- Transit PINX (ISO/IEC 11582)
- User (ISO/IEC 11574)
- User A, Transferring user (ISO/IEC 19459)
- User B, Transferred user (ISO/IEC 19459)
- User C, Transferred-to user (ISO/IEC 19459)
4.2 Other definitions
4.2.1 Rerouting number : The number of the Transferred-to user.
4.2.2 Rerouting PINX : A PINX on the call path of the original call, that reroutes that call to user C. This can either be the
Transferring, the Transferred or a Transit PINX being capable of performing the rerouting function.
4.2.3 Transferred PINX : The End PINX which is on the end of the original call nearest to user B.
4.2.4 Transferred-To PINX : The End PINX which is on the end of the new call nearest to user C.
4.2.5 Transferring PINX : The End PINX which initiates single step call transfer procedures on behalf of user A.
5 Acronyms
APDU Application Protocol Data Unit
ASN.1 Abstract Syntax Notation no. 1
ISDN Integrated Services Digital Network
NFE Network Facility Extension
PICS Protocol Implementation Conformance Statement
PINX Private Integrated services Network eXchange
PISN Private Integrated Services Network
SDL Specification and Description Language
SS-SSCT Supplementary Service Single Step Call Transfer
© ISO/IEC 2001 – All rights reserved 3

6 Signalling protocol for the support of SS-SSCT
6.1 SS-SSCT description
SS-SSCT is a supplementary service which enables a user, user A, to transform an existing call between user A and user B into
a new call between user B and a user C whereby user A does not have a call established with user C prior to call transfer.
This supplementary service is applicable to all basic services defined in ISO/IEC 11574.
6.2 SS-SSCT operational requirements
6.2.1 Provision/Withdrawal
Provision and withdrawal shall be in accordance with 6.2.1 of ISO/IEC 19459.
6.2.2 Requirements on a Transferring PINX
The basic call procedures specified in ISO/IEC 11572 shall be supported.
Generic procedures for the call-related control of supplementary services, as specified in ISO/IEC 11582 for an End PINX,
shall apply.
6.2.3 Requirements on a Rerouting PINX
The basic call procedures specified in ISO/IEC 11572 shall be supported.
Generic procedures for the call-related control of supplementary services, as specified in ISO/IEC 11582 for an End PINX,
shall apply.
6.2.4 Requirements on a Transferred PINX
The basic call procedures specified in ISO/IEC 11572 shall be supported.
Generic procedures for the call-related control of supplementary services, as specified in ISO/IEC 11582 for an End PINX,
shall apply.
6.2.5 Requirements on a Transferred-To PINX
The basic call procedures specified in ISO/IEC 11572 shall be supported.
Generic procedures for the call-related control of supplementary services, as specified in ISO/IEC 11582 for an End PINX,
shall apply.
6.2.6 Requirements on a Transit PINX
The basic call procedures specified in ISO/IEC 11572 shall be supported.
Generic procedures for the call-related control of supplementary services, as specified in ISO/IEC 11582 for a Transit PINX,
shall apply.
© ISO/IEC 2001 – All rights reserved
6.3 SS-SSCT coding requirements
6.3.1 Operations
The following operations, defined in Abstract Syntax Notation number 1 (ASN.1) in table 1 shall apply.
Table 1 - Operations in support of SS-SSCT
Single-Step-Call-Transfer-Operations
{iso(1) standard (0)
pss1-single-step-call-transfer (19460) single-step-call-transfer-operations (0)}
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
IMPORTS
OPERATION, ERROR FROM Remote-Operation-Notation
{ joint-iso-ccitt (2) remote-operations (4) notation (0) }
Extension FROM Manufacturer-specific-extension-definition
{ iso (1) standard (0) pss1-generic-procedures (11582) msi-definition (0) }
Name FROM Name-Operations
{iso(1) standard(0) pss1-name (13868) name-operations (0)}
supplementaryServiceInteractionNotAllowed, notAvailable, invalidCallState
FROM General-Error-List
{ ccitt recommendation q 950 general-error-list (1) }
PresentedAddressScreened, PartyNumber FROM Addressing-Data-Elements
{iso(1) standard (0) pss1-generic-procedures (11582)
addressing-data-elements (9)}
PSS1InformationElement FROM pss1-generic-parameters-definition
{iso(1) standard (0) pss1-generic-procedures (11582)
pss1-generic-parameters (6)}
callTransferUpdate, callTransferComplete, callTransferActive, subaddressTransfer,
invalidReroutingNumber, establishmentFailure FROM Call-Transfer-Operations
{iso(1) standard (0) pss1-call-transfer (13869) call-transfer-operations(0)};
SsctInitiate ::= OPERATION
-- sent from the Transferring PINX to the Rerouting PINX
ARGUMENT SSCTInitiateArg
RESULT DummyRes
ERRORS { notAvailable, invalidCallState, invalidRerouteingNumber,
establishmentFailure, unspecified,
supplementaryServiceInteractionNotAllowed }
SsctSetup ::= OPERATION
-- sent from the Rerouting PINX to the Transferred-To PINX
ARGUMENT SSCTSetupArg
SsctPostDial ::= OPERATION
-- sent from the Rerouting PINX to the Transferred PINX
ARGUMENT DummyArg
© ISO/IEC 2001 – All rights reserved 5

Table 1 - Operations in support of SS-SSCT (continued)
SsctDigitlnfo ::= OPERATION
-- sent from the Transferred PINX to the Rerouting PINX
ARGUMENT SSCTDigitInfoArg
DummyArg ::= CHOICE {
null NULL,
single [1] IMPLICIT Extension,
multiple [2] IMPLICIT SEQUENCE OF Extension }
DummyRes ::= CHOICE {
null NULL,
single [1] IMPLICIT Extension,
multiple [2] IMPLICIT SEQUENCE OF Extension }
SSCTInitiateArg ::= SEQUENCE {
rerouteingNumber PartyNumber, -- Transferred-To Number
transferredAddress PresentedAddressScreened,
awaitConnect AwaitConnect,
transferredName[1] Name OPTIONAL,
transferringAddress [2] PresentedAddressScreened OPTIONAL,
transferringName [3] Name OPTIONAL,
argumentExtension CHOICE {
single [4] IMPLICIT Extension,
multiple [5] IMPLICIT SEQUENCE OF Extension
}OPTIONAL
}
AwaitConnect ::= BOOLEAN
-- FALSE = release the original call upon ALERTING received
-- TRUE = release the original call upon CONNECT received
SSCTSetupArg ::= SEQUENCE {
transferringAddress [1] PresentedAddressScreened OPTIONAL,
transferringName [2] Name OPTIONAL,
argumentExtension CHOICE {
single [3] IMPLICIT Extension,
multiple [4] IMPLICIT SEQUENCE OF Extension
}OPTIONAL
}
SSCTDigitInfoArg ::= SEQUENCE {
reroutingNumber [1] PartyNumber OPTIONAL,
-- remaining digits of the Transferred-To Number
sendingComplete [2] IMPLICIT NULL OPTIONAL,
argumentExtension CHOICE {
single [3] IMPLICIT Extension,
multiple [4] IMPLICIT SEQUENCE OF Extension
}OPTIONAL
}
© ISO/IEC 2001 – All rights reserved
Table 1 - Operations in support of SS-SSCT (concluded)
Unspecified ::= ERROR PARAMETER Extension
unspecified Unspecified :: = localValue 1008
ssctInitiate SsctInitiate :: = localValue 99
ssctSetup SsctSetup :: = localValue 100
ssctPostDial SsctPostDial :: = localValue 101
ssctDigitInfo SsctDigitInfo :: = localValue 102
END -- of SSCT Operations
6.3.2 Information elements
6.3.2.1 Facility information element
APDUs of the operations defined in 6.3.1 shall be coded in the Facility information element in accordance with ISO/IEC
11582.
When conveying the invoke APDU of the operations defined in 6.3.1, the destinationEntity data element of the NFE shall
contain value endPINX.
When conveying the invoke APDU of operation ssctSetup, the Interpretation APDU shall contain value
discardAnyUnrecognisedInvokePdu.
When conveying the invoke APDU of operations ssctInitiate, ssctPostDial or ssctDigitInfo the Interpretation APDU shall be
included with the value rejectAnyUnrecognisedInvokePdu or omitted.
6.3.2.2 Information elements embedded in the Facility information element
APDUs of the operations defined in 6.3.1 may contain information elements defined in and coded according to ISO/IEC
11572. These shall be embedded in data elements of type PSS1InformationElement as specified in annex B of ISO/IEC 11582.
6.3.2.3 Other information elements
Information elements used during the establishment of the new connection shall be coded as specified in ISO/IEC 11572.
6.3.3 Messages
Except for cases where a basic call message is to be conveyed at the same time, the Facility information element shall be
conveyed in a FACILITY message as specified in ISO/IEC 11582.
Messages used during the establishment of the new connection and release of the original connection shall be as specified in
ISO/IEC 11572 and, where applicable, augmented in ISO/IEC 11582.
6.4 SS-SSCT state definitions
6.4.1 States at a Transferring PINX
The procedures at the Transferring PINX are written in terms of the following conceptual states existing within the SS-SSCT
control entity in that PINX in association with a particular SS-SSCT request from the transferring user.
6.4.1.1 SSCT-Idle
SS-SSCT is not operating.
6.4.1.2 SSCT-Await-Initiate-Response
A ssctInitiate invoke APDU has been sent to the Rerouting PINX.
6.4.2 States at a Rerouting PINX
The procedures at the Rerouting PINX are written in terms of the following conceptual states existing within the SS-SSCT
control entity in that PINX.
6.4.2.1 SSCT-Idle
SS-SSCT is not operating.
© ISO/IEC 2001 – All rights reserved 7

6.4.2.2 SSCT-Await-Setup-Response-Alert
A ssctInitiate invoke APDU has been received with element waitConnect set to FALSE. A ssctSetup invoke APDU has been
sent to the Transferred-To PINX.
6.4.2.3 SSCT-Await-Setup-Response-Connect
A ssctInitiate invoke APDU has been received with element waitConnect set to TRUE. A ssctSetup invoke APDU has been
sent to the Transferred-To PINX.
6.4.2.4 SSCT-Await-Info
A ssctPostDial invoke APDU has been sent to the Transferred PINX and further address information can be received in
overlap mode.
6.4.3 States at a Transferred PINX
The procedures at the Transferred PINX are written in terms of the following conceptual states existing within the SS-SSCT
control entity in that PINX in association with the original call, i.e. a particular call of the transferred user.
6.4.3.1 CT-Idle
SS-SSCT is not operating.
NOTE 1 - As the Transferred PINX acts in the same way as a SS-CT Primary PINX in case of SS-CT by join sub-clause 6.4.2.1 (States at a
Primary PINX - CT-Idle) of ISO/IEC 13869 applies accordingly.
6.4.4 States at a Transferred-To PINX
The procedures at the Transferred-To PINX are written in terms of the following conceptual states existing within the SS-
SSCT control entity in that PINX.
6.4.4.1 SSCT-Idle
SS-SSCT is not operating.
6.5 SS-SSCT signalling procedures
References in this clause to protocol control states refer to basic call protocol control states defined in ISO/IEC 11572.
NOTE 2 - The specification in this section is based on each of the End PINXs being a different PINX, but this section is also applicable to
scenarios where two or more of the four PINXs are the same. In those scenarios some of the signalling procedures and message flows
described in this section are internal to the PINX implementation and therefore outside the scope of this International Standard.
Annex C contains some examples of message sequences.
6.5.1 Actions at a Transferring PINX
The SDL representation of procedures at a Transferring PINX is shown in D.1 of annex D.
6.5.1.1 Normal Procedures
On receipt of a valid request for SS-SSCT from user A while in state SSCT-Idle for a call between user B and user A which is
in protocol control state Active (the original call), the Transferring PINX shall
- send a ssctInitiate invoke APDU in a FACILITY message towards the Transferred PINX using the call reference of the
original call. The ssctInitiate invoke APDU shall include the following elements:
· awaitConnect set to TRUE if the original call shall be released after a CONNECT message from the Transferred-To
PINX and set to FALSE if it shall be released on receipt of an ALERTING message from the Transferred-To PINX;
· rerouteingNumber set to the party number of the transferred-to user (i.e., user C), as far as available;
· transferredAddress set to the address of the transferred user, i.e. user B;
· optionally transferredName set to the name of the transferred user, i.e. user B;
· optionally elements transferringAddress and transferringName set to the address and name of the transferring user, i.e.
user A;
-startTimerT1;
- enter state SSCT-Await-Initiate-Response.
On receipt in state SSCT-Await-Initiate-Response of a DISCONNECT message with a ssctInitiate return result APDU from
the Rerouting PINX, using the call reference of the original call, the Transferring PINX shall continue call clearing of the
original call according to basic call procedures, stop timer T1, and enter state SSCT-Idle.
© ISO/IEC 2001 – All rights reserved
6.5.1.2 Exceptional Procedures
On receipt in state SSCT-Await-Initiate-Response of a message using the call reference of the original call, and conveying a
ssctInitiate reject or return error APDU, the Transferring PINX shall stop timer T1, abort the procedure for single step call
transfer and enter state SSCT-Idle. The original call shall continue.
On expiry of timer T1, the Transferring PINX shall abort the procedure for single step call transfer and enter state SSCT-Idle.
The original call shall continue.
Upon receiving in state SSCT-Await-Initiate-Response an indication from basic call control that the original call has been
cleared, the Transferring PINX shall stop Timer T1 and enter state SSCT-Idle.
6.5.2 Procedures at the Rerouting PINX
The SDL representation of procedures at a Rerouting PINX is shown in D.2 of annex D.
6.5.2.1 Normal procedures
On receipt in state SSCT-Idle of a FACILITY message containing a ssctInitiate invoke APDU while in protocol control state
Active, the Rerouting PINX shall determine whether it can perform the SSCT rerouting request. If so, it shall attempt to
establish a new connection by selecting a route determined by the contents of rerouteingNumber (i.e. to the Transferred-To
PINX) received within the argument of ssctInitiate. If a B-channel is available and if enough digits of the reroutingNumber are
present, a SETUP message shall be sent using a new call reference in accordance with the procedures of ISO/IEC 11572. The
SETUP message shall contain the following information elements:
- Bearer capability, containing the Bearer Capability information of the original call;
- Called party number, containing the number received in rerouteingNumber within the received ssctInitiate invoke APDU;
- Calling party number, containing the number received in transferredAddress within the received ssctInitiate invoke APDU;
- Facility, conveying a ssctSetup invoke APDU with optional elements transferringAddress and transferring Name set as
within the received ssctInitiate invoke APDU and optionally conveying a callingName invoke APDU indicating the Name
data as received within data element transferredName of the ssctInitiate invoke APDU;
- optionally Calling party subaddress, containing the subaddress information from element transferredAddress within the
received ssctInitiate invoke APDU.
If the element awaitConnect within the received ssctInitiate invoke APDU was set to TRUE, state SSCT-Await-Setup-
Response-Connect shall be entered. If the element was set to FALSE, state SSCT-Await-Setup-Response-Alert shall be
entered.
The protocol procedures of ISO/IEC 11572 shall apply during the establishment of the new connection.
If the reroutingNumber received within the argument of ssctInitiate invoke APDU is not complete, a ssctPostDial invoke
APDU shall be sent to the Transferred PINX, the Rerouting PINX shall enter state SSCT-Await-Info and start timer T3. While
in state SSCT-Await-Info, additional information received in the element reroutingNumber of a ssctDigitInfo invoke APDU in
a FACILITY message shall be used to select a route for call extension or, if the call has already been extended, passed on to
the Subsequent PINX in accordance with ISO/IEC 11572. If the Rerouting PINX regards the number information as complete,
or if a sendingComplete element contained in ssctDigitInfo invoke APDU is received, the Rerouting PINX shall process any
number information present in the argument, stop timer T3 and initiate call establishment towards the Transferred-To PINX in
accordance with ISO/IEC 11572 if not already done and, depending on the element awaitConnect received within the
ssctInitiate invoke APDU (see above), enter state SSCT-Await-Setup-Response-Connect or state SSCT-Await-Setup-
Response-Alert. Otherwise it shall restart timer T3 and remain in state SSCT-Await-Info. On receipt in state SSCT-Await-Info
of a CALL PROCEEDING message. Timer T3 shall be stopped and, depending on the element awaitConnect received within
the ssctInitiate invoke APDU (see above), enter state SSCT-Await-Setup-Response-Connect or state SSCT-Await-Setup-
Response-Alert.
On receipt in state SSCT-Await-Info of an ALERTING message. Timer T3 shall be stopped and, if the element awaitConnect
received within the ssctInitiate invoke APDU is set to TRUE optionally start T2 and enter SSCT-Await-Setup-Response-
Connect; otherwise if element awaitConnect is set to FALSE proceed as described below for receiving an ALERTING
message in state SSCT-Await-Setup-Response-Alert.
On receipt in state SSCT-Await-Info of a CONNECT message timer, T3 shall be stopped and proceed as described below for
receiving a CONNECT message in state SSCT-Await-Setup-Response-Connect.
On receipt in state SSCT-Await-Setup-Response-Alert of an ALERTING or a CONNECT message, using the call reference of
the new connection the Rerouting PINX shall
© ISO/IEC 2001 – All rights reserved 9

- disconnect the B-channel of the original call and connect the Transferred PINX to the B-channel of the new connection;
- send a DISCONNECT message containing a ssctInitiate return result APDU on the call reference of the original call to the
Transferring PINX (completion of the release of the old connection shall be in accordance with the protocol procedures of
ISO/IEC 11572);
- send a callTransferComplete invoke APDU within a FACILITY message on the call reference of the original call to the
Transferred PINX, element callStatus set to alerting (on receipt of an ALERTING message) or to answered (on receipt of a
CONNECT message);
- enter state SSCT-Idle.
On receipt in state SSCT-Idle of a CONNECT message using the call reference of the new connection, the Rerouting PINX
shall send a callTransferActive invoke APDU within a FACILITY message on the call reference of the original call to the
Transferred PINX.
On receipt in state SSCT-Await-Setup-Response-Connect of an ALERTING message (using the call reference of the new
connection), the Rerouting PINX shall
- remain in state SSCT-Await-Setup-Response-Connect;
- optionally start Timer T2.
On receipt in state SSCT-Await-Setup-Response-Connect of a CONNECT message on the call reference of the new
connection, indicating call acceptance by user C, the Rerouting PINX shall
- stop Timer T2 (if started);
- disconnect the B-channel of the original call and connect the Transferred PINX to the B-channel of the new connection;
- send a callTransferComplete invoke APDU within a FACILITY message on the call reference of the original call to the
Transferred PINX, element callStatus set to answered;
- send a DISCONNECT message containing a ssctInitiate return result APDU on the call reference of the original call to the
Transferring PINX. Completion of the release of the old connection shall be in accordance with the protocol procedures of
ISO/IEC 11572;
- enter state SSCT-Idle.
The above mentioned callTransferComplete and callTransferActive invoke APDU's shall contain information as specified in
ISO/IEC 13869.
If the received ALERTING or CONNECT messages also contain a callTransferUpdate invoke APDU with, in the argument,
optional elements redirectionNumber, redirectionName and/or basicCallInfoElements, the callTransferUpdate invoke APDU
shall be sent to the Transferred PINX within a FACILITY message.
6.5.2.2 Exceptional procedures
If on receipt in state SSCT-Idle of a FACILITY message containing a ssctInitiate invoke APDU and the SSCT rerouting
request can not be performed,, the Rerouting PINX shall send a ssctInitiate return error APDU containing error value
"notAvailable" to the Transferring PINX in a FACILITY message on the call reference on which the invoke was received.
On expiry of timer T2, or on expiry of T3 if the number information received is not sufficient to proceed or on receipt in state
SSCT-Await-Setup-Response-Alert or SSCT-Await-Setup-Response-Connect or SSCT-Await-Info of a call clearing message
on the call reference of the new connection, the Rerouting PINX shall
- proceed with call clearing of the new connection in accordance with the procedures of ISO/IEC 11572;
- send a FACILITY message on the call reference of the original call to the Transferring PINX, conveying a ssctInitiate
return error APDU, indicating error value establishmentFailure;
- stop Timer T2 (if started);
- stop Timer T3 (if started);
- enter state SSCT-Idle.
On receipt in state SSCT-Await-Setup-Response-Alert, SSCT-Await-Setup-Response-Connect or SSCT-Await-Info of a call
clearing message on the call reference of the original call, the Rerouting PINX shall
- proceed with call clearing of the original call in accordance with the procedures of ISO/IEC 11572 (acting as a Transit
PINX);
© ISO/IEC 2001 – All rights reserved
- initiate call clearing of the new call using the procedures of ISO/IEC 11572;
- stop Timer T2 (if started);
- stop Timer T3 (if started);
- enter state SSCT-Idle.
If timer T3 expires and if the number information received so far is considered sufficient, initiate call establishment towards
the Transferred-To PINX in accordance with ISO/IEC 11572, if not already done, and depending on the element awaitConnect
received within ssctInitiate invoke APDU (see above), enter state SSCT-Await-Setup-Response-Connect or state SSCT-Await-
Setup-Response-Alert.
A ssctDigitInfo invoke APDU received in any other state than SSCT-Await-Info shall be ignored.
6.5.3 Actions at a Transferred PINX
The SDL representation of procedures at a Primary PINX is shown in D.3 of annex D.
6.5.3.1 Normal procedures
As the Transferred PINX acts in the same way as a SS-CT Primary PINX in case of SS-CT by join, sub-clause 6.5.2.1 of
ISO/IEC 13869 shall apply accordingly.
On receipt in state SSCT-Idle of a FACILITY message from the Rerouting PINX containing a ssctPostDial invoke APDU,
additional address information from the transferred user B shall be included in the element reroutingNumber of ssctDigitInfo
invoke APDUs and sent in FACILITY messages to the Rerouting PINX. The end of number information transmission may be
indicated to the Rerouting PINX by means of a sendingComplete element within the ssctDigitInfo invoke APDU.
6.5.3.2 Exceptional procedures
As the Transferred PINX acts in the same way as a SS-CT Primary PINX in case of SS-CT by join, sub-clause 6.5.2.2 of
ISO/IEC 13869 shall apply accordingly.
6.5.4 Actions at a Transferred-To PINX
The SDL representation of procedures at a Transferred-To PINX is shown in D.4 of annex D.
6.5.4.1 Normal procedures
Having agreed the B-channel and sent back a SETUP ACKNOWLEDGE or a CALL PROCEEDING message in response to
an incoming SETUP message, in accordance with the procedures of ISO/IEC 11572, if the SETUP contains a ssctSetup invoke
APDU, the Transferred-To PINX shall proceed as follows. The Transferred-To PINX may record details of the transfer, may
notify the transferred user, and may solicit a subaddress for sending to user B.
The call establishment shall proceed according to the procedures of ISO/IEC 11572.
6.5.4.2 Exceptional procedures
Not applicable.
6.5.5 Actions at a Transit PINX
No special actions are required in support of SS-SSCT.
6.5.6 Subsequent actions at Transferred and Transferred-To PINX
As the Transferred PINX acts in the same way as a SS-CT Primary PINX in case of SS-CT by join, and the Transferred-To
PINX acts for the subsequent actions as a SS-CT Secondary PINX in case of SS-CT by join, sub-clause 6.5.5 of ISO/IEC
13869 shall apply accordingly.
6.6 SS-SSCT impact of interworking with public ISDNs
6.6.1 Actions at a Gateway PINX
As no similar service is available within a public ISDN, SS-SSCT has to be invoked by a PISN user A and also the Rerouting
PINX has to be placed within the PISN.
Interworking aspects are different depending on the type of interworking situation, the two relevant types are:
- User B is in the public ISDN,
- User C is in the public ISDN,
these two scenarios can be combined, i.e. both users (B and C) can be within the public ISDN.
© ISO/IEC 2001 – All rights reserved 11

6.6.1.1 Impact of interworking if User B is in the public ISDN
Single Step Call Transfer is performed within the PISN and the Gateway PINX shall act as Transferred PINX.
If the signalling protocol at the access allows, the Gateway PINX shall indicate that transfer has occurred, together with
relevant information e.g. transferringNumber, and the number and/or subaddress of the Transferred-to user in appropriate
notifications or operations to the public ISDN.
If subaddress information is subsequently received from the public ISDN it shall be forwarded to the Transferred-To PINX as
data element connectedSubaddress in a subaddressTransfer invoke APDU within a FACILITY message. For this scenario only
complete numbers are allowed.
6.6.1.2 Impact of interworking if User C is in the public ISDN
Single Step Call Transfer is performed within the PISN and the Gateway PINX shall act as Transferred-To PINX.
If the signalling protocol at the access allows, the Gateway PINX shall indicate that transfer has occurred, together with
relevant information e.g. transferringNumber, and the number and/or subaddress of the transferred user in appropriate
notifications or operations to the public ISDN.
If subaddress information is subsequently received from the public ISDN it shall be forwarded to the Transferred PINX as data
element connectedSubaddress in a subaddressTransfer invoke APDU within a FACILITY message.
6.7 SS-SSCT impact of interworking with non-ISDNs
6.7.1 Actions at a Gateway PINX
If no similar service is available within a non-ISDN, SS-SSCT has to be invoked by a PISN user A and also the Rerouting
PINX has to be placed within the PISN.
When user A is in the PISN, and user B (user C) is in the non-ISDN, single step call transfer shall be performed within the
PISN, and the gateway PINX shall act as Transferred (Transferred-To) PINX. For this scenario only complete numbers are
allowed.
The gateway shall perform for single step call transfer a signalling mapping between the signalling system specified in this
International Standard and that of the non-ISDN.
6.8 Protocol Interactions between SS-SSCT and other supplementary services and ANFs
This clause specifies protocol interactions with other supplementary services and ANFs for which stage 3 standards had been
published at the time of publication of this International Standard. For interactions with supplementary services and ANFs for
which stage 3 standards are published subsequent to the publication of this International Standard, see those other stage 3
standards.
NOTE 3 - Simultaneous conveyance of APDUs for SS-SSCT and another supplementary service or ANF in the same message, each in
accordance with the requirements of its respective stage 3 standard, does not, on its own, constitute a protocol interaction.
NOTE 4 - Additional interactions that have no impact on the signalling protocol at the Q reference point can be found in the relevant stage 1
specifications.
6.8.1 Calling Name Identification Presentation (SS-CNIP)
Protocol interactions are specified in 6.5.
6.8.2 Connected Name Identification Presentation (SS-CONP)
Protocol interactions are specified in 6.5.
NOTE 5 - For details see also ISO/IEC 13869.
6.8.3 Comp
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