SIST ETS 300 392-10-13 E2:2003
(Main)Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D); Part 10: Supplementary services stage 1; Sub-part 13: Call completion to busy subscriber
General Information
- Abstract
Analysis of predicted needs for digital trunked systems in Europe; definition of services to be provided; analysis of spectrum req ments; characteristics of relevant interfaces Contains: TETRA 03.60 to 03.85
- Status
- Published
- Publication Date
- 30-Nov-2003
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 01-Dec-2003
- Due Date
- 01-Dec-2003
- Completion Date
- 01-Dec-2003
- Mandate
- T-172-1A
Overview
SIST ETS 300 392-10-13 E2:2003 defines the stage 1 specification for the supplementary service "Call Completion to Busy Subscriber" (CCBS) within Terrestrial Trunked Radio (TETRA) systems. This European standard, developed by the Slovenian Institute for Standardization (SIST), is part of the TETRA Voice plus Data (V+D) series, specifically addressing the requirements and operational procedures for providing efficient call completion services when the target subscriber is busy.
The standard supports the ongoing evolution of digital trunked radio systems in Europe, focusing on user-needs analysis, service definitions, and spectrum use for TETRA-based networks. Proper implementation of supplementary services like CCBS enhances operational efficiency and user experience in professional mobile radio environments.
Keywords: TETRA, supplementary services, call completion, CCBS, digital trunked radio, V+D, stage 1, radio communication standards
Key Topics
Call Completion to Busy Subscriber (SS-CCBS):
- Enables automatic recall or call re-attempt when a previously busy subscriber becomes available.
- Enhances communication efficiency by reducing manual redial efforts.
- Applicable to both voice and data services within TETRA networks.
Service Provision & Withdrawal:
- Provisioning by network operators to eligible users.
- Can be withdrawn by user request or for administrative reasons.
- No user-specific subscription options; general applicability.
Operational Procedures:
- Involves timers for service duration, retention, recall, and list request activities.
- Handles activation, deactivation, and cancellation of SS-CCBS requests.
- Details interactions when multiple requests exist or when group calls are involved.
Exceptional Handling:
- Manages conditions such as network congestion, duplicate requests, and unavailability of SS-CCBS support.
- Specifies user notifications and cancellation criteria.
Interworking and Interactions:
- Specifies interactions with other supplementary services such as call forwarding, call waiting, and identification services.
- Addresses behavior during group calls and in scenarios with both individual and group busy states.
Applications
The SS-CCBS service is invaluable in industries where uninterrupted, reliable communication is critical, such as:
- Public safety and emergency services: Ensures that calls reach busy controllers or responders as soon as their line becomes available.
- Transportation and logistics: Reduces wait times and missed connections for dispatch and coordination staff.
- Utilities and industrial operations: Improves productivity by automating connection attempts in busy network conditions.
Deploying SS-CCBS according to this standard means:
- Enhanced user experience: Automatic re-attempts reduce manual intervention.
- Operational efficiency: Decreases delays and communication gaps in high-traffic or mission-critical environments.
- Interoperability: Clear guidelines for how SS-CCBS interacts with related services, ensuring predictable behavior across devices and networks.
Related Standards
- ETS 300 392-2: TETRA; Voice plus Data (V+D); Part 2: Air Interface.
- ETS 300 392-9: TETRA; General requirements for supplementary services.
- ECMA-185: Private Integrated Services Network (PISN); Functional Model and Information Flows; Call Completion Supplementary Services.
- ITU-T Recommendation I.210: Principles for telecommunication services in ISDN.
- TS 101 282 (GSM 02.93): Completion of Calls to Busy Subscriber in GSM.
These related standards help ensure consistent, compatible implementation of supplementary services in digital trunked radio systems, facilitating broader adoption and reliable service delivery across European networks.
For organizations deploying TETRA communications, adherence to SIST ETS 300 392-10-13 E2:2003 ensures that call completion to busy subscribers is handled efficiently, increasing overall system effectiveness and user satisfaction.
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Frequently Asked Questions
SIST ETS 300 392-10-13 E2:2003 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D); Part 10: Supplementary services stage 1; Sub-part 13: Call completion to busy subscriber". This standard covers: Analysis of predicted needs for digital trunked systems in Europe; definition of services to be provided; analysis of spectrum req ments; characteristics of relevant interfaces Contains: TETRA 03.60 to 03.85
Analysis of predicted needs for digital trunked systems in Europe; definition of services to be provided; analysis of spectrum req ments; characteristics of relevant interfaces Contains: TETRA 03.60 to 03.85
SIST ETS 300 392-10-13 E2:2003 is classified under the following ICS (International Classification for Standards) categories: 33.070.10 - Terrestrial Trunked Radio (TETRA). The ICS classification helps identify the subject area and facilitates finding related standards.
SIST ETS 300 392-10-13 E2:2003 is associated with the following European legislation: Standardization Mandates: T-172-1A. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
SIST ETS 300 392-10-13 E2:2003 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2003
3UL]HPQLVQRSRYQLUDGLR7(75$±*RYRULQSRGDWNL9'±GHO'RSROQLOQH
VWRULWYHVWRSQMH±SRJODYMH'RNRQþDQMHNOLFDQMD]DVHGHQHJDQDURþQLND
Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D); Part 10: Supplementary
services stage 1; Sub-part 13: Call completion to busy subscriber
Ta slovenski standard je istoveten z: ETS 300 392-10-13 Edition 2
ICS:
33.070.10 Prizemni snopovni radio Terrestrial Trunked Radio
(TETRA) (TETRA)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN ETS 300 392-10-13
TELECOMMUNICATION September 1999
STANDARD Second Edition
Source: TETRA Reference: RE/TETRA-03001-10-13
ICS: 33.020
Key words: CCBS, data, radio, speech, stage 1, supplementary service, TETRA
Terrestrial Trunked Radio (TETRA);
Voice plus Data (V+D);
Part 10: Supplementary services stage 1;
Sub-part 13: Call completion to busy subscriber
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Internet: secretariat@etsi.fr - http://www.etsi.org
Tel.: +33 4 92 94 42 00 - Fax: +33 4 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 1999. All rights reserved.
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ETS 300 392-10-13: September 1999
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 Standards Making Support Dept." at the address shown on the title page.
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ETS 300 392-10-13: September 1999
Contents
Foreword . 5
1 Scope. 7
2 References. 7
3 Definitions, symbols and abbreviations. 8
3.1 Definitions. 8
3.2 Symbols. 10
3.3 Abbreviations. 10
3.3.1 General abbreviations. 10
3.3.2 Supplementary service abbreviations . 10
4 SS-CCBS Stage 1 Specification . 11
4.1 Description. 11
4.1.1 General description. 11
4.1.2 Qualifications on applicability to telecommunication services. 11
4.2 Procedures . 11
4.2.1 Provision/Withdrawal . 11
4.2.2 Normal procedures . 12
4.2.2.1 Activation/deactivation/registration/Interrogation. 12
4.2.2.2 Invocation and operation. 12
4.2.2.3 Cancellation. 13
4.2.2.4 Group call considerations. 13
4.2.2.5 Timers . 13
4.2.3 Exceptional Procedures. 13
4.2.3.1 Activation/deactivation/registration/interrogation. 13
4.2.3.2 Invocation and Operation . 14
4.2.3.2.1 Rejection of SS-CCBS Service
request. 14
4.2.3.2.2 User A is busy on SS-CCBS recall. 14
4.2.3.2.3 Network congestion. 14
4.2.3.2.4 User B becomes busy after SS-CCBS
recall. 15
4.2.3.2.5 Duplicate SS-CCBS requests. 15
4.2.3.2.6 Other situations . 15
4.2.3.2.7 Other failure situations . 15
4.2.3.3 Cancellation. 15
4.3 Interactions with other supplementary services and ANFs . 15
4.3.1 Calling Line Identification Presentation (SS-CLIP) . 16
4.3.2 Connected Line Identification Presentation (SS-COLP) . 16
4.3.3 Calling/Connected Line Identification Restriction (SS-CLIR). 16
4.3.4 Completion of Calls on No Reply (SS-CCNR) . 16
4.3.5 Call Forwarding Unconditional (SS-CFU) . 16
4.3.5.1 SS-CFU activated by user B before user A requests SS-
CCBS . 16
4.3.5.2 SS-CFU activated by user B after user A requests SS-
CCBS . 16
4.3.5.3 SS-CFU activation by user A. 16
4.3.6 Call Forwarding Busy (SS-CFB) . 16
4.3.6.1 SS-CFB activated by user B before user A requests SS-
CCBS . 16
4.3.6.2 SS-CFB activated by user B after user A requests SS-
CCBS . 16
4.3.6.3 SS-CFB activation by user A. 16
4.3.7 Call Forwarding on No Reply (SS-CFNR). 17
4.3.8 Call Report (SS-CR) . 17
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ETS 300 392-10-13: September 1999
4.3.9 Talking Party Identification (SS-TPI) .17
4.3.10 Call Forwarding on Not Reachable (SS-CFNR ) .17
c
4.3.11 List Search Call (SS-LSC).17
4.3.12 Call Authorized by Dispatcher (SS-CAD) .17
4.3.13 Short Number Addressing (SS-SNA) .17
4.3.14 Area Selection (SS-AS).17
4.3.15 Access Priority (SS-AP) .18
4.3.16 Priority Call (SS-PC).18
4.3.17 Call Waiting (SS-CW) .18
4.3.18 Call Hold (SS-HOLD) .18
4.3.19 Late Entry (SS-LE) .18
4.3.20 Transfer of Control (SS-TC).18
4.3.21 Pre-emptive Priority Call (SS-PPC).18
4.3.22 Include Call (SS-IC).18
4.3.23 Advice of Charge (SS-AoC) .18
4.3.24 Barring of Outgoing Calls (SS-BOC).18
4.3.25 Barring of Incoming Calls (SS-BIC).18
4.3.26 Discreet Listening (SS-DL).19
4.3.27 Ambiance Listening (SS-AL) .19
4.3.28 Dynamic Group Number Assignment (SS-DGNA).19
4.3.29 Call Retention (SS-CRT).19
4.3.30 Interaction with ANFs .19
4.3.30.1 Mobility.19
4.3.30.1.1 Migration of user B while SS-CCBS is
active for a given call .19
4.3.30.1.2 Migration of user A while SS-CCBS is
active.19
4.3.30.1.3 Migration of either user A or user B to
a SwMI not supporting SS-CCBS .19
4.3.31 Inter-working considerations .19
4.4 SS-CCBS overall SDL .20
Annex A (informative): Bibliography.23
History.24
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ETS 300 392-10-13: September 1999
Foreword
This European Telecommunication Standard (ETS) has been produced by the Terrestrial Trunked Radio
(TETRA) Project of the European Telecommunications Standards Institute (ETSI).
This ETS is a multi-part standard and will consist of the following parts:
Part 1: "General network design";
Part 2: "Air Interface (AI)";
Part 3: "Interworking at the Inter-System Interface (ISI)";
Part 4: "Gateways basic operation";
Part 5: "Peripheral Equipment Interface (PEI)";
Part 6: "Line connected Station (LS)";
Part 7: "Security";
Part 9: "General requirements for supplementary services";
Part 10: "Supplementary services stage 1";
Part 11: "Supplementary services stage 2";
Part 12: "Supplementary services stage 3";
Part 13: "SDL model of the Air Interface (AI)";
Part 14: "Protocol Implementation Conformance Statement (PICS) proforma specification".
Transposition dates
Date of adoption of this ETS: 3 September 1999
Date of latest announcement of this ETS (doa): 31 December 1999
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 30 June 2000
Date of withdrawal of any conflicting National Standard (dow): 30 June 2000
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ETS 300 392-10-13: September 1999
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ETS 300 392-10-13: September 1999
1 Scope
This ETS specifies the Call Completion on Busy Subscriber (SS-CCBS) supplementary service which is
applicable to various basic services supported by TETRA Switching and Management Infrastructures
(SwMIs). TETRA basic services are specified in ETS 300 392-2 [8].
SS-CCBS allows completion of a call to a subscriber that was unsuccessful because of a busy condition
without making a new call attempt.
Supplementary service specifications are produced in three stages, according to the method described in
ITU-T Recommendation I.210 [4]. This ETS contains the stage 1 specifications of SS-CCBS. The stage 1
descriptions specify the supplementary services as seen by users of SwMIs.
This ETS is applicable to circuit mode TETRA tele-services and bearer services only. This ETS does not
address the case where the MS/LS is not reachable. SS-CCBS assumes MS/LS is reachable.
Man Machine Interfaces and charging principles are outside the scope of this ETS.
This first edition of this ETS was presented as a delta document to the first edition of ECMA-185 [2]. This
version has been redrafted based on the latest published text of ECMA-185 [2] as a self-contained
document so as to be more readable. Additions to ECMA-185 [2] have been made to take into account
particular TETRA specifics (e.g. group call) and to include user requirements and situations not addressed
in ECMA-185 [2].
NOTE: Contrary to PISN SS-CCBS and SS-CCNR which are both specified in ECMA-185 [2],
TETRA SS-CCBS and TETRA SS-CCNR are specified in two separate ETSs.
2 References
This ETS incorporates by dated and undated reference, provisions from other publications. These
references are cited at the appropriate places in the text and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this ETS
only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies.
[1] Void.
[2] Standard ECMA-185 (1997): "Private Integrated Services Network (PISN);
Specification, Functional Model and Information Flows; Call Completion
Supplementary Services (CCSD)".
[3] ITU-T Recommendation I.112 (1993): "Vocabulary of terms for ISDNs".
[4] ITU-T Recommendation I.210 (1993): "Principles of telecommunication services
supported by an ISDN and the means to describe them".
[5] ITU-T Recommendation I.221 (1993): "Common specific characteristics of
services".
[6] ITU-T Recommendation Z.100 (1993): "CCITT specification and description
language (SDL)".
[7] Void.
[8] ETS 300 392-2 (1996): "Terrestrial Trunked Radio (TETRA); Voice plus Data
(V+D); Part 2: Air Interface (AI)".
[9] ETS 300 392-9 (1997): "Terrestrial Trunked Radio (TETRA); Voice plus Data
(V+D); Part 9: General requirements for supplementary services".
[10] CCITT Recommandation Q.9 (1988): "Vocabulary of switching and signalling
terms".
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ETS 300 392-10-13: September 1999
[11] TS 101 282: "Digital cellular telecommunications system (Phase 2+);
Completion of Calls to Busy Subscriber (CCBS); Service description, Stage 1
(GSM 02.93 version 6.0.1 Release 1997)".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of this ETS, the following definitions apply:
Additional Network Feature: Capability, over and above that of a basic service, provided by a SwMI, but
not directly to a user.
basic (…) service: Any stand alone bearer service or tele-service (derived from ITU-T
Recommendation I.210 [4]).
bearer service: type of telecommunication service that provides the capability for the transmission of
signals between user-network interfaces (as defined in ITU-T Recommendation I.112 [3]).
busy: Property of a user for whom either a "network determined user busy" or "user determined user
busy" condition (see subclause 3.1 of ITU-T Recommendation I.221 [5]) exists.
call, basic call: Instance of the use of a basic service.
call completion: Successful presentation of a previously unsuccessful Call to a destination user (user B)
which occurs when the call has entered an alerting phase or has been answered.
NOTE 1: CCBS call completion could result in a CCNR condition in which case user A would
invoke SS-CCNR and not SS-CCBS anymore.
CCBS busy: Any one of the following conditions will cause user A to be considered as CCBS busy:
- maximum number of calls queued at user A;
- CCBS recall pending on user A;
- no resource available at user A.
NOTE 2: It is assumed that SS-CCNR busy is independent from SS-CCBS busy; one could
consider merging the two conditions in an SS-CC busy which would combine the total
numbers of CCBS and CCNR requests.
compatible MS/LS: MS/LS presenting the same basic TETRA class of service as the TETRA class of
service requested by the calling user MS/LS. By analogy to ISDN "compatible terminal".
free: Property of a user who can accept any attempt by the SwMI to present a call to that user (i.e. allow
the call to reach the alerting or answered state).
group busy: group is busy when group controlling SwMI determines that group is busy; group busy shall
generally be equivalent to NDUB.
NOTE 3: How the SwMi determines group busy condition is implementation dependent and is
outside the scope of this draft ETS.
idle guard time: Time the network will wait after user B has become free before initiating a “CCBS recall”
to user A (definition from TS 101 282 [11]).
Line Station (LS): Physical grouping that contains all the fixed equipment that is used to obtain TETRA
services through a line.
Mobile Station (MS): Physical grouping that contains all of the mobile equipment that is used to obtain
TETRA services. By definition, a mobile station contains at least one Mobile Radio Stack (MRS).
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ETS 300 392-10-13: September 1999
Network Determined User Busy: Analogy to ISDN, when all available interface resources are busy, the
busy shall be network determined user busy.
path reservation: Reservation of resources just prior to SS-CCBS Recall in order that a connection path
through the network is available when user A accepts the SS-CCBS Recall.
NOTE 4: Path Reservation would not guarantee that user B will be free when user A accepts the
SS-CCBS Recall.
NOTE 5: Path Reservation is not the preferred mode of operation in the TERA environment due
to mobility considerations.
recall timer: Timer specifies the length of time the network shall wait for a response from user A to a
CC Recall.
retention timer: Timer specifies the period of time the network retains the originating call information after
a valid call attempt is released.
SS-CCBS busy: See CCBS busy.
SS-CCBS call: Call generated by the network from user A to user B resulting from user A's acceptance of
a SS-CCBS recall.
SS-CCBS recall: Indication informing user A that user B is no longer busy (in the case of SS-CCBS).
Acceptance of this indication by user A will cause the call to be completed by the SwMI.
SS-CCBS request: Instance of an activation of SS-CCBS held in a queue pending the correct conditions
for the SS-CCBS to be completed.
SS-CCBS service duration timer: Timer specifies the length of time that the service shall be active
within the network.
supplementary service: Any service provided by a network in addition to its basic service or services
(defined in CCITT Recommendation Q.9 [10]). A supplementary service modifies or supplements a basic
telecommunication service. Consequently, it cannot be offered to a customer as a stand alone service. It
must be offered together with or in association with a basic telecommunication service (except from
ITU-T Recommendation I.210 [4]).
suspended CCBS request: CCBS request that cannot be served even if destination B is not busy,
because user A is busy or CCBS busy.
Switching and Management Infrastructure (SwMI): All of the TETRA equipment for a Voice plus Data
(V+D) network except for subscriber terminals. The SwMI enables subscriber terminals to communicate
with each other via the SwMI.
tele-service: Type of telecommunications service that provides the complete capability, including terminal
equipment functions, for communication between users according to agreed protocols.
User A: Specific user that originated the call and requested the supplementary service.
User B: User that was initially addressed in the original individual call set up. In the case of a group call,
Group (B) will be used in place of user B.
user B idle guard timer: See idle guard timer definition.
User Determined User Busy: Analogy to ISDN, busy shall be user determined user busy when
subscriber resources (either the terminal itself or the user) do not respond positively to an incoming call
request.
NOTE 6: In the case where the MS/LS has a single resource and is involved in an individual call,
UDUB and NDUB will be confounded. In other words, NDUB could result of a single
call occurrence.
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ETS 300 392-10-13: September 1999
NOTE 7: It appears, after further investigation, that UDUB will never happen in a TETRA Mobile
Station; however, the definition of UDUB is left to clarify the distinction with NDUB and
for the case of inter-working.
3.2 Symbols
For the purposes of this ETS, there are no special symbols besides the symbol used in SDL diagram and
defined in ITU-T Recommendation Z.100 [6].
3.3 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
3.3.1 General abbreviations
AI Air Interface
ANF Additional Network Feature
CC Call Control (functional entity)
CC Call Completion (generic term for both CCBS and CCNR)
CCBS Completion of Calls to Busy Subscribers
CCNR Completion of Calls on No Reply
GTSI Group TETRA Subscriber Identity
ISDN Integrated Services Digital Network
ISI Interworking at the Inter-System Interface
LS Line Station
MS Mobile Station
NDUB Network Determined User Busy
PICS Protocol Implementation Conformance Statement
PISN Private Integrated Services Network
SDL Specification and Description Language
SS Supplementary Service
NOTE: The abbreviation SS is only used when referring to a specific supplementary service.
SwMI Switching and Management Infrastructure
TETRA TErrestrial Trunked RAdio
TE Terminal Equipment
UDUB User Determined User Busy
V+D Voice Plus Data
3.3.2 Supplementary service abbreviations
AL Ambiance Listening
AoC Advice of Charge
AP Access Priority
AS Area Selection
BIC Barring of Incoming Calls
BOC Barring of Outgoing Calls
CAD Call Authorized by Dispatcher
CCBS Call Completion to Busy Subscriber
CCNR Call Completion on No Reply
CFB Call Forwarding on Busy
CFNRy Call Forwarding on No Reply
CFNRc Call Forwarding on Not Reachable
CFU Call Forwarding Unconditional
CLIP Calling Line Identification Presentation
CLIR Calling/Connected Line Identification Restriction
COLP COnnected Line Identification Presentation
CR Call Report
CRT Call Retention
CW Call Waiting
DGNA Dynamic Group Number Assignment
DL Discreet Listening
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ETS 300 392-10-13: September 1999
HOLD Call Hold
IC Include Call
LE Late Entry
LSC List Search Call
MRS Mobile Radio Stack
PC Priority Call
PEI Peripheral Equipment Interface
PPC Pre-emptive Priority Call
SNA Short Number Addressing
TC Transfer of Control
TPI Talking Party Identification
4 SS-CCBS Stage 1 Specification
4.1 Description
4.1.1 General description
SS-CCBS is offered to a calling user (user A). On encountering a busy condition at the called user
(user B), SS-CCBS may be offered to the calling user (user A). If user A invokes SS-CCBS, the SwMI B
shall monitor user B. If user B becomes not busy and stays free during the ‘idle guard time’ (user B does
not place an outgoing call and does not receive an incoming call with higher priority than the pending
CCBS call), user A is notified that user B is not busy. On positive response by user A to that notification,
the SwMI shall attempt to complete the call to user B.
4.1.2 Qualifications on applicability to telecommunication services
This supplementary service is applicable to all basic circuit mode TETRA V+D services.
4.2 Procedures
4.2.1 Provision/Withdrawal
SS-CCBS may be provided after pre-arrangement with the service provider (to selected users), or may be
generally available to all users. SS-CCBS may be withdrawn on request of the user or for administrative
reasons.
No subscription options shall be offered by the SwMI.
NOTE 1: Contrary to ECMA-185 which offers two subscription options for recall mode,
SS-CCBS Recall shall be offered only to the terminal which has invoked SS-CCBS.
NOTE 2: As a guidance to stage 3 ETS, the following main options in relation to ECMA 185 are
selected for TETRA SS-CCBS:
- Path reservation is not provided;
NOTE 3: In the TETRA network environment, path reservation is deemed not to be necessary
due to mobility considerations; a path reserved between two SwMIs could become not
available when one of the user migrates.
- Signaling connection is retained for the duration of the SS-CCBS request;
- Retention of the SS-CCBS service until expiration of the service duration timer (if user A and/or
user B is found busy after the recall).
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ETS 300 392-10-13: September 1999
4.2.2 Normal procedures
4.2.2.1 Activation/deactivation/registration/Interrogation
SS-CCBS shall be permanently activated upon provision and permanently deactivated upon withdrawal.
User B needs not to have subscribed to SS-CCBS for calling user A invocation of SS-CCBS to operate
properly.
Restriction of SS-CCBS for called user B is outsi
...



