ETSI EN 300 267-1 V1.2.2 (1998-04)
Integrated Services Digital Network (ISDN); Telephony 7 kHz, videotelephony, audiographic conference and videoconference teleservices; Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol specification
Integrated Services Digital Network (ISDN); Telephony 7 kHz, videotelephony, audiographic conference and videoconference teleservices; Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol specification
REN/SPS-05112-1
Digitalno omrežje z integriranimi storitvami (ISDN) - Daljinske storitve: telefonija 7 kHz, videotelefonija, avdiografična konferenca in videokonferenca - Protokol digitalne naročniške signalizacije št. 1 (DSS1) - 1. del: Specifikacija protokola
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2005
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Integrated Services Digital Network (ISDN); Telephony 7 kHz, videotelephony,
audiographic conference and videoconference teleservices; Digital Subscriber Signalling
System No. one (DSS1) protocol; Part 1: Protocol specification
Ta slovenski standard je istoveten z: EN 300 267-1 Version 1.2.2
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 300 267-1 V1.2.2 (1998-04)
European Standard (Telecommunications series)
Integrated Services Digital Network (ISDN);
Telephony 7 kHz, videotelephony, audiographic conference
and videoconference teleservices;
Digital Subscriber Signalling System No. one (DSS1) protocol;
Part 1: Protocol specification
2 EN 300 267-1 V1.2.2 (1998-04)
Reference
REN/SPS-05112-1 (2h090ipc.PDF)
Keywords
ISDN, DSS1, teleservice, 7 kHz, audio, video,
telephony, CONF, protocol
ETSI
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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 1998.
All rights reserved.
ETSI
3 EN 300 267-1 V1.2.2 (1998-04)
Contents
Intellectual Property Rights.6
Foreword .6
1 Scope.8
2 Normative references .9
3 Definitions.10
4 Abbreviations.11
5 Additional generic requirements for basic telecommunication services not defined in
EN 300 403-1 .11
5.1 Description. 11
5.2 Operational requirements. 11
5.3 Coding requirements. 12
5.4 State definitions . 12
5.5 Signalling procedures at the coincident S and T reference point . 12
5.5.1 Procedures for establishment of a second or subsequent connection within the same call. 12
5.5.1.1 Normal operation. 12
5.5.1.2 Exceptional procedures. 13
5.5.2 Provision of in-band tones and announcements . 13
5.6 Procedures for interworking with private ISDNs. 13
5.6.1 Procedures for the establishment of a second connection within the same call. 13
5.6.2 Provision of in-band tones and announcements . 13
5.7 Interactions with other networks. 13
5.8 Parameter values (timers). 13
5.9 Dynamic description (SDL diagrams). 14
6 Telephony 7 kHz teleservice.14
6.1 Description. 14
6.2 Operational requirements. 14
6.2.1 Provision and withdrawal. 14
6.2.2 Requirements on the originating network side . 15
6.2.3 Requirements on the destination network side . 15
6.3 Coding requirements. 15
6.4 State definitions . 15
6.5 Signalling procedures at the coincident S and T reference point . 15
6.5.1 Call establishment at the originating interface. 15
6.5.2 Call establishment at the destination interface . 17
6.5.2.1 First connection . 17
6.5.2.2 Further connections . 17
6.5.3 Call clearing . 18
6.5.4 In-band tones and announcements. 18
6.5.5 Restart procedure . 18
6.5.6 Call rearrangements. 18
6.5.7 Call collisions. 18
6.5.8 Handling of error conditions . 18
6.5.9 User notification procedure. 18
6.5.10 Basic telecommunication service identification and selection. 19
6.5.11 Signalling procedures for bearer capability selection. 19
6.5.12 Signalling procedures for high layer compatibility selection . 19
6.5.13 Status request procedures. 19
6.6 Procedures for interworking with private ISDNs. 19
6.7 Interactions with other networks. 20
6.8 Parameter values (timers). 20
6.9 Dynamic description (SDL diagrams). 20
ETSI
4 EN 300 267-1 V1.2.2 (1998-04)
7 Videotelephony teleservice.20
7.1 Description. 20
7.2 Operational requirements. 21
7.2.1 Provision and withdrawal. 21
7.2.2 Requirements on the originating network side . 21
7.2.3 Requirements on the destination network side . 21
7.3 Coding requirements. 21
7.4 State definitions . 22
7.5 Signalling procedures at the coincident S and T reference point . 22
7.5.1 Call establishment at the originating interface. 22
7.5.2 Call establishment at the destination interface . 24
7.5.2.1 First connection . 24
7.5.2.2 Further connections . 25
7.5.3 Call clearing . 25
7.5.4 In-band tones and announcements. 26
7.5.5 Restart procedures. 26
7.5.6 Call rearrangements. 26
7.5.7 Call collisions. 26
7.5.8 Handling of error conditions . 26
7.5.9 User notification procedure. 26
7.5.10 Basic telecommunication service identification and selection. 27
7.5.11 Signalling procedures for bearer capability selection. 27
7.5.12 Signalling procedures for high layer compatibility selection . 27
7.5.13 Status request procedures. 27
7.6 Procedures for interworking with private ISDNs. 27
7.7 Interactions with other networks. 28
7.8 Parameter values (timers). 29
7.9 Dynamic description (SDL diagrams). 29
8 Audiographic conference teleservice.29
8.1 Description. 29
8.2 Operational requirements. 30
8.2.1 Provision and withdrawal. 30
8.2.2 Requirements on the originating network side . 30
8.2.3 Requirements on the destination network side . 30
8.3 Coding requirements. 30
8.4 State definitions . 30
8.5 Signalling procedures at the coincident S and T reference point . 31
8.5.1 Call establishment at the originating interface. 31
8.5.1.1 First connection . 31
8.5.1.2 Further connections . 33
8.5.2 Call establishment at the destination interface . 33
8.5.2.1 First connection . 33
8.5.2.2 Further connections . 34
8.5.3 Call clearing . 35
8.5.4 In-band tones and announcements. 35
8.5.5 Restart procedures. 35
8.5.6 Call rearrangements. 35
8.5.7 Call collisions. 35
8.5.8 Handling of error conditions . 35
8.5.9 User notification procedure. 36
8.5.10 Basic telecommunication service identification and selection. 36
8.5.11 Signalling procedures for bearer capability selection. 36
8.5.12 Signalling procedures for high layer compatibility selection . 36
8.5.13 Status request procedures. 36
8.6 Procedures for interworking with private ISDNs. 36
8.6.1 First connection. 36
8.6.2 Further connections. 38
8.7 Interactions with other networks. 38
8.8 Parameter values (timers). 38
8.9 Dynamic description (SDL diagrams). 38
ETSI
5 EN 300 267-1 V1.2.2 (1998-04)
9 Videoconference teleservice .38
9.1 Description. 38
9.2 Operational requirements. 39
9.2.1 Provision and withdrawal. 39
9.2.2 Requirements on the originating network side . 39
9.2.3 Requirements on the destination network side . 39
9.3 Coding requirements. 39
9.4 State definitions . 40
9.5 Signalling procedures at the coincident S and T reference point . 40
9.5.1 Call establishment at the originating interface. 40
9.5.1.1 First connection . 40
9.5.1.2 Further connections . 42
9.5.2 Call establishment at the destination interface . 42
9.5.2.1 First connection . 42
9.5.2.2 Further connections . 43
9.5.3 Call clearing . 43
9.5.4 In-band tones and announcements. 44
9.5.5 Restart procedures. 44
9.5.6 Call rearrangements. 44
9.5.7 Call collisions. 44
9.5.8 Handling of error conditions . 44
9.5.9 User notification procedure. 44
9.5.10 Basic telecommunication service identification and selection. 44
9.5.11 Signalling procedures for bearer capability selection. 45
9.5.12 Signalling procedures for high layer compatibility selection . 45
9.5.13 Status request procedures. 45
9.6 Procedures for interworking with private ISDNs. 45
9.6.1 First connection. 45
9.6.2 Further connections. 46
9.7 Interactions with other networks. 46
9.8 Parameter values (timers). 47
9.9 Dynamic description (SDL diagrams). 47
Annex A (informative): Signalling flows for the telephony 7 kHz teleservice.48
Annex B (informative): Signalling flows for the videotelephony teleservice.51
Annex C (informative): Signalling flows for the audiographic conference teleservice .55
Annex D (informative): Signalling flows for the videoconference teleservice.59
Annex E (informative): Identification of changes from previous standards.63
E.1 Identification of changes from ETS 300 267-1 to its amendment A1 .63
E.2 Identification of changes from ETS 300 267-1 including amendment A1 to the present document.64
Annex F (informative): Bibliography.65
History.66
ETSI
6 EN 300 267-1 V1.2.2 (1998-04)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETR 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of
ETSI standards", which is available free of charge from the ETSI Secretariat. Latest updates are available on the ETSI
Web server (http://www.etsi.fr/ipr or http://www.etsi.org/ipr).
Pursuant to the ETSI Interim IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No
guarantee can be given as to the existence of other IPRs not referenced in ETR 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This European Standard (Telecommunications series) has been produced by ETSI Technical Committee Signalling
Protocols and Switching (SPS).
The present document is part 1 of a multi-part standard covering the Digital Subscriber Signalling System No. one
(DSS1) protocol specification for the Integrated Services Digital Network (ISDN) telephony 7 kHz, videotelephony,
audiographic conference and videoconference teleservices, as described below:
Part 1: "Protocol specification";
Part 2: "Protocol Implementation Conformance Statement (PICS) proforma specification";
Part 3: "Test Suite Structure and Test Purposes (TSS&TP) specification for the user";
Part 4: "Abstract Test Suite (ATS) and partial Protocol Implementation eXtra Information for Testing (PIXIT)
proforma specification for the user";
Part 5: "Test Suite Structure and Test Purposes (TSS&TP) specification for the network";
Part 6: "Abstract Test Suite (ATS) and partial Protocol Implementation eXtra Information for Testing (PIXIT)
proforma specification for the network".
Information in the present document concerning usage of the in-band protocol has been prepared in association with
ETSI Technical Committee Terminal Equipment (TE); such information is outside the scope of Technical Committee
SPS but has been included here to improve the presentation for implementors.
In accordance with CCITT Recommendation I.130, the following three level structure is used to describe the
telecommunication services as provided by European public telecommunications operators under the pan-European
ISDN:
- Stage 1: is an overall service description, from the user's standpoint;
- Stage 2: identifies the functional capabilities and information flows needed to support the service described in
stage 1; and,
- Stage 3: defines the signalling system protocols and switching functions needed to implement the service
described in stage 1.
The present document details the stage 3 aspects (DSS1 protocol) needed to support the telephony 7 kHz,
videotelephony, audiographic conference and videoconference teleservices.
ETSI
7 EN 300 267-1 V1.2.2 (1998-04)
The telephony 7 kHz stage 1 and stage 2 aspects are detailed in ETS 300 263 and ETS 300 265, respectively.
The videotelephony stage 1 and stage 2 aspects are detailed in ETS 300 264 and ETS 300 266, respectively.
The audiographic conference stage 1 aspects are detailed in ETS 300 675.
The videoconference stage 1 aspects are detailed in ETS 300 678.
The present document is an extended and updated version of ETS 300 267-1 (1994) and its amendment A1 (1996).
Annex E identifies relevant differences between the present document and these standards.
National transposition dates
Date of adoption of this EN: 3 April 1998
Date of latest announcement of this EN (doa): 31 July 1998
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 January 1999
Date of withdrawal of any conflicting National Standard (dow): 31 January 1999
ETSI
8 EN 300 267-1 V1.2.2 (1998-04)
1 Scope
This first part of EN 300 267 specifies the stage three of the videotelephony, telephony 7 kHz, audiographic conference
and videoconference teleservices for the pan-European Integrated Services Digital Network (ISDN) as provided by
European public telecommunications operators at the T reference point or coincident S and T reference point (as defined
in ITU-T Recommendation I.411 [4]) by means of the Digital Subscriber Signalling System No. one (DSS1) protocol.
Stage three identifies the protocol procedures and switching functions needed to support a telecommunication service
(see CCITT Recommendation I.130 [3]).
In addition, the present document specifies the protocol requirements at the T reference point where the service is
provided to the user via a private ISDN.
The present document does not specify the additional protocol requirements where the service is provided to the user via
a telecommunication network that is not an ISDN.
For the telephony 7 kHz, videotelephony, audiographic conference and videoconference teleservices, the present
document specifies procedures for commencement of the in-band protocol by normative reference to the relevant in-
band protocol ETSs.
The present document also specifies additional procedures to those required to support basic call in EN 300 403-1 [16]
in order to support the four teleservices described in the present document. These additional procedures may be used to
support other basic telecommunication services.
The telephony 7 kHz teleservice is a real-time teleservice in which speech (7 kHz or 3,1 kHz bandwidth) can be
interchanged using one circuit-mode 64 kbit/s connection.
The videotelephony teleservice is a real-time, audiovisual teleservice in which speech and moving pictures are
interchanged by means of one or two 64 kbit/s circuit-mode connections in the ISDN. The picture information
transmitted is sufficient for adequate representation of fluid movements of a person displayed in head and shoulders
view.
The audiographic conference teleservice is a real-time teleservice in which high quality speech, control signals and data
are interchanged using one or more circuit-mode 64 kbit/s connection(s).
The videoconference teleservice is a real-time teleservice in which high quality audio, video, control signals and data are
interchanged using two or more circuit-mode 64 kbit/s connections.
Procedures for the correlation of independent connections within the same videotelephony, audiographic conference or
videoconference call are outside the scope of the present document. This places responsibility on the user of this service
to avoid situations where certain supplementary services are being used, and also situations where multiple calls are
being presented to the same user at the same time.
Further parts of the present document specify the method of testing required to identify conformance to the present
document.
The present document is applicable to equipment supporting the videotelephony, telephony 7 kHz, audiographic
conference and videoconference teleservices, to be attached at either side of a T reference point or coincident S and T
reference point when used as an access to the public ISDN.
ETSI
9 EN 300 267-1 V1.2.2 (1998-04)
2 Normative references
References may be made to:
a) specific versions of publications (identified by date of publication, edition number, version number, etc.), in
which case, subsequent revisions to the referenced document do not apply; or
b) all versions up to and including the identified version (identified by "up to and including" before the version
identity); or
c) all versions subsequent to and including the identified version (identified by "onwards" following the version
identity); or
d) publications without mention of a specific version, in which case the latest version applies.
A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same
number.
[1] CCITT Recommendation G.711 (1988): "Pulse code modulation (PCM) of voice frequencies".
[2] ITU-T Recommendation I.112 (1993): "Vocabulary of terms for ISDNs".
[3] CCITT Recommendation I.130 (1988): "Method for the characterization of telecommunication
services supported by an ISDN and network capabilities of an ISDN".
[4] ITU-T Recommendation I.411 (1993): "ISDN user-network interfaces - Reference configurations".
[5] CCITT Recommendation Q.9 (1988): "Vocabulary of switching and signalling terms".
[6] ETS 300 092-1: "Integrated Services Digital Network (ISDN); Calling Line Identification
Presentation (CLIP) supplementary service; Digital Subscriber Signalling System No. one (DSS1)
protocol; Part 1: Protocol specification".
[7] ETS 300 097-1: "Integrated Services Digital Network (ISDN); Connected Line Identification
Presentation (COLP) supplementary service; Digital Subscriber Signalling System No. one (DSS1)
protocol; Part 1: Protocol specification".
[8] ETS 300 143: "Integrated Services Digital Network (ISDN); Audiovisual services; Inband
signalling procedures for audiovisual terminals using digital channels up to 2 048 kbit/s"
(equivalent to ITU-T Recommendation H.242).
[9] ETS 300 144: "Integrated Services Digital Network (ISDN); Audiovisual services; Frame structure
for a 64 kbit/s to 1 920 kbit/s channel and associated syntax for in-band signalling" (equivalent to
ITU-T Recommendation H.221).
[10] ETS 300 145: "Integrated Services Digital Network (ISDN); Audiovisual services; Videotelephone
systems and terminal equipment operating on one or two 64 kbit/s channels".
[11] EN 300 196-1 (V1.2): "Integrated Services Digital Network (ISDN); Generic functional protocol
for the support of supplementary services; Digital Subscriber Signalling System No. one (DSS1)
protocol; Part 1: Protocol specification".
[12] I-ETS 300 245-2: "Integrated Services Digital Network (ISDN); Technical characteristics of
telephony terminals; Part 2: PCM A-law handset telephony".
[13] I-ETS 300 245-5: "Integrated Services Digital Network (ISDN); Technical characteristics of
telephony terminals; Part 5: Wideband (7 kHz) handset telephony".
[14] ETS 300 263 (1994): "Integrated Services Digital Network (ISDN); Telephony 7 kHz teleservice;
Service description".
[15] ETS 300 264 (1994): "Integrated Services Digital Network (ISDN); Videotelephony teleservice;
Service description".
ETSI
10 EN 300 267-1 V1.2.2 (1998-04)
[16] EN 300 403-1 (V1.2): "Integrated Services Digital Network (ISDN); Digital Subscriber Signalling
System No. one (DSS1) protocol; Signalling network layer for circuit-mode basic call control;
Part 1: Protocol specification [ITU-T Recommendation Q.931 (1993), modified]".
[17] ETS 300 403-2: "Integrated Services Digital Network (ISDN); Digital Subscriber Signalling
System No. one (DSS1) protocol; Signalling network layer for circuit-mode basic call control;
Part 2: Specification and Description Language (SDL) diagrams".
[18] ETS 300 675: "Integrated Services Digital Network (ISDN); Audiographic conference teleservice;
Service description".
[19] ETS 300 678: "Integrated Services Digital Network (ISDN); Videoconference teleservice; Service
description".
3 Definitions
The following definitions apply:
basic telecommunication service: A telecommunication service that is either a teleservice or a bearer service.
bearer capability: The type of transmission media provided by the network, and thus the type of the overall connection,
and also the set of lower layer protocols required on the connection.
bearer service: See ITU-T Recommendation I.112 [2], definition 202.
bearer: An association of transmission channels or circuits, and switching, set up to provide a means for transfer of
information between two or more points in a telecommunication network. It does not include control signalling.
call control message: A message as defined in EN 300 403-1 [16], subclause 3.1, which on sending or receipt causes a
change of the call state at either the network or the user. A call control message thus indicates or causes a change in the
state of the bearer. Call control messages also include the INFORMATION message and PROGRESS message.
call reference: An identifier of a signalling transaction. The signalling transaction may either be bearer related, in which
case the signalling transaction can be used to control that bearer, or bearer independent, in which case there is no bearer
associated with that signalling transaction. Where there is only one bearer required for a call, then the call reference of
the associated bearer-related signalling transaction may be used to identify the call.
call state: A state as defined in EN 300 403-1 [16] subclause 2.1 for either the user or the network as appropriate. A call
state may exist for each call reference value (and for each additional responding CEI in the incoming call states). This
represents the state of a state machine associated with a bearer-related or bearer-independent signalling transaction. For
a bearer-related signalling transaction the call state also identifies the condition of the associated bearer, and where a
call consists of only one bearer, may also identify the condition of the call.
call: See CCITT Recommendation Q.9 [5], definition 2201.
connection type: See ITU-T Recommendation I.112 [2], definition 316.
connection: See CCITT Recommendation Q.9 [5], definition 0011. In the present document the use of this term is taken
to include a bearer and its associated control signalling.
data link connection endpoint identifier; Connection Endpoint Identifier (CEI): Identifier used by a layer 3
protocol entity to address its peer entity.
fallback: The mechanism for selecting, at the time of call request and establishment, an alternative bearer capability, or
high layer compatibility, to that primarily requested by the calling user. Fallback may occur either due to the network
being unable to provide the primarily requested bearer capability, or high layer compatibility, or due to the called user
desiring an alternative bearer capability, or high layer compatibility.
high layer compatibility: The set of higher layer protocols required for the call; this information may also be used to
define the basic telecommunication service as a particular teleservice.
ETSI
11 EN 300 267-1 V1.2.2 (1998-04)
in-band protocol entity: The protocol entity within the terminal responsible for the provision of the in-band procedures
(e.g. I-ETS 300 245-2 [12], ETS 300 143 [8], I-ETS 300 245-5 [13]).
Integrated Services Digital Network (ISDN): See ITU-T Recommendation I.112 [2], definition 308.
network: The DSS1 protocol entity at the network side of the user-network interface.
service; telecommunication service: See ITU-T Recommendation I.112 [2], definition 201.
teleservice: See ITU-T Recommendation I.112 [2], definition 203.
user: The DSS1 protocol entity at the user side of the user-network interface.
4 Abbreviations
For the purposes of the present document, the following abbreviations apply:
CEI Connection Endpoint Identifier
DSS1 Digital Subscriber Signalling System No. one
ISDN Integrated Services Digital Network
PSTN Public Switched Telephone Network
SDL Specification and Description Language
5 Additional generic requirements for basic
telecommunication services not defined in
EN 300 403-1
5.1 Description
Clause 5 provides generic requirements for the provision of the telephony 7 kHz, videotelephony, audiographic
conference and videoconference basic telecommunication services that are not contained in other ETSs (e.g.
EN 300 403-1 [16]). The specification of a basic telecommunication service can be simplified by normative reference to
the appropriate generic procedures within clause 5. These generic procedures form requirements for a basic
telecommunication service only when such a normative reference is made.
NOTE: This approach has been adopted in the specification of the telephony 7 kHz teleservice in clause 6, in the
specification of the videotelephony teleservice in clause 7, in the specification of the audiographic
conference teleservice in clause 8 and in the specification of the videoconference teleservice in clause 9.
Other basic telecommunication services outside the scope of the present document can be specified in this
manner.
These additional generic requirements have been defined to be compatible with the existing requirements of
EN 300 403-1 [16].
5.2 Operational requirements
Operational requirements are specified for each basic telecommunication service (for example, see subclause 6.2,
subclause 7.2, subclause 8.2, and subclause 9.2).
ETSI
12 EN 300 267-1 V1.2.2 (1998-04)
5.3 Coding requirements
The message structures defined in subclause 3.1 of EN 300 403-1 [16] shall apply. The message structures defined in
subclause 3.4 of EN 300 403-1 [16] are applicable to accesses supporting the telephony 7 kHz, the videotelephony, the
audiographic conference and the videoconference teleservices, but their use is outside the scope of the present
document.
The information elements defined in subclause 4.5 of EN 300 403-1 [16] shall apply, with the addition that the
Connected number and the Connected subaddress information elements defined in ETS 300 097-1 [7], clause 7, shall
also be used.
5.4 State definitions
The call states defined in subclause 2.1 of EN 300 403-1 [16] shall apply.
The states defined in subclause 2.4 of EN 300 403-1 [16] are applicable to accesses supporting the telephony 7 kHz,
videotelephony, audiographic conference and videoconference teleservices, but are outside the scope of the present
document.
5.5 Signalling procedures at the coincident S and T reference
point
5.5.1 Procedures for establishment of a second or subsequent connection
within the same call
NOTE: Prior to the following procedures, and for the establishment of the first connection, other procedures take
place according to EN 300 403-1 [16], clause 5.
5.5.1.1 Normal operation
Where the basic telecommunication service requires a second or subsequent connection, in addition to a first connection
the following procedures apply:
a) the originating user shall include in the Bearer capability information element, included in the SETUP message
requesting the first connection, a specification of an appropriate in-band signalling protocol;
NOTE 1: ETS 300 144 [9] and ETS 300 143 [8] form an appropriate in-band signalling protocol which can be
requested within the Bearer capability information element by setting the information transfer field to
"unrestricted digital information" or "unrestricted digital information with tones/announcements" and
setting the layer one protocol fi
...
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