ETSI ETS 300 233 ed.1 (1994-05)

SLOVENSKI STANDARD
01-december-2003
Digitalno omrežje z integriranimi storitvami (ISDN) – Dostopovni digitalni oddelek
za primarne funkcije ISDN
Integrated Services Digital Network (ISDN); Access digital section for ISDN primary rate
Ta slovenski standard je istoveten z: ETS 300 233 Edition 1
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.

EUROPEAN ETS 300 233
TELECOMMUNICATION May 1994
STANDARD
Source: ETSI TC-TM Reference: DE/TM-03003
ICS: 33.020
Transmission, multiplexing, ISDN
Key words:
Integrated Services Digital Network (ISDN);
Access digital section for ISDN primary rate
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - secretariat@etsi.fr
X.400: Internet:
Tel.: +33 92 94 42 00 - Fax: +33 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1994. All rights reserved.
New presentation - see History box

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ETS 300 233: May 1994
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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ETS 300 233: May 1994
Contents
Foreword.5
1 Scope .7
2 Normative references .7
3 Definitions and abbreviations.8
3.1 Definitions.8
3.2 Abbreviations.8
4 Configuration and application.9
4.1 Configuration .9
4.2 Application.11
4.3 Modelling and relationship between the access digital section and the ET.11
5 Functions.13
5.1 B-channel .13
5.2 H0-channel .13
5.3 H1-channel .13
5.4 D-channel .13
5.5 Bit timing .14
5.6 Octet timing.14
5.7 Frame alignment .14
5.8 CRC-4 procedure.14
5.9 M-channel.14
5.10 Power feeding .14
5.11 Operation and maintenance of the access digital section.14
6 Signal transfer delay.14
7 Jitter .15
7.1 Output/input jitter at T reference point.15
7.2 Jitter at the V3 reference point.15
8 Operation and maintenance.15
8.1 Control facilities .15
8.1.1 Loopbacks.15
8.1.1.1 Loopback implementation.15
8.1.1.2 Loopback procedure.15
8.2 Monitoring .15
8.2.1 Functions.15
8.2.2 Defect conditions and consequent actions .16
8.2.2.1 Detection of defect conditions.16
8.2.2.2 Definition of defect indication signals .16
8.2.2.3 Detection of defect indication signals.17
8.2.2.4 Definition of detection algorithms.17
8.2.2.5 Consequent actions .18
8.3 Error performance monitoring.18
9 Operation and maintenance procedures.18
9.1 Partitioning of functions.18
9.2 Definitions of signals at the T reference point .20
9.3 Definition of signals at the V3 reference point.20
9.4 Definition of ET layer 1 state machine.24

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ETS 300 233: May 1994
9.5 Definition of DS state machine.24
9.5.1 DS states .24
9.5.2 DS state transition table.24
9.5.2.1 Assumptions.25
9.5.2.2 Classification of DS states.25
9.5.2.3 Definition of notations.25
9.5.2.4 NOTES to DS state tables 5a to 5j.55
Annex A (normative): System management requirements.56
A.1 Introduction.56
A.2 System management requirements .56
A.2.1 General .56
A.2.2 Error indications .56
A.2.3 Loopback operations .56
A.2.4 Information to be sent in the D-channel during loopback operation.57
A.2.5 Configuration control.57
A.3 Handling of CRC error information in the ET.57
A.4 Definition of ET layer 1 state machine .57
A.4.1 ET layer 1 states.57
A.4.2 PH and MPH primitives .57
A.4.2.1 The repertoire of PH and MPH primitives.57
A.4.2.2 Repertoire of MPH primitives.57
A.4.3 ET layer 1 state transition table.58
A.4.3.1 Definition of notations.58
A.4.3.2 Classification of ET states.59
Annex B (normative): Combined ET and LT functions.73
Annex C (normative): Conformance testing .73
Annex D (informative): Bibliography.73
Annex E (informative): NT1 functions with 2 048 kbit/s and Option 2.74
History .75

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ETS 300 233: May 1994
Foreword
This European Telecommunication Standard (ETS) has been produced by the Transmission and
Multiplexing (TM) Technical Committee of the European Telecommunications Standards Institute (ETSI).
Annexes A to C of this ETS are normative whereas Annexes D and E are informative.
NOTE: ITU-T Recommendation G.962 (1993) is based upon this ETS.

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ETS 300 233: May 1994
Blank page
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ETS 300 233: May 1994
1 Scope
This ETS specifies the characteristics of an access digital section for the Integrated Services Digital
Network (ISDN) primary rate access between the user-network interface (at the T reference point, defined
in ETS 300 011 [1]) and the local exchange (at the V.3 reference point, defined in CCITT Recommendation
Q.512 [4]) supporting the primary rate interface channel structure defined in CCITT Recommendation
I.412 [3] and ETS 300 011 [1] and the additional functions required for operation and maintenance of the
access digital section according to ETR 001 [2], Option 2.
NOTE: ITU-T Recommendation G.962 (1993) is based upon this ETS.
The requirements of this ETS satisfy network performance requirements of CCITT Recommendations
G.821 [5] on error performance as well as CCITT Recommendations G.801 and I.350 with regard to
availability.
Annex A (normative) to this ETS specifies requirements for interworking between the Primary Rate Access
Digital Section (DS) and the Exchange Termination (ET) and the definition of the ET layer 1 state machine
which are outside the scope of this ETS but which are nevertheless important.
Annex B (normative) specifies a modification of the requirements when Line Termination (LT) and ET
functions are combined in one unit.
Annex C (normative), to be provided, will specify the requirements for conformance testing.
This ETS does not specify the requirements of the digital transmission system used within the access
digital section.
2 Normative references
This ETS incorporates by dated or undated reference, provisions from other publications. These normative
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] ETS 300 011 (1992): "Integrated Services Digital Network (ISDN); Primary rate
user-network interface; layer 1 specification and test principles".
[2] ETR 001: "Integrated Services Digital Network (ISDN); Customer access
maintenance".
[3] CCITT Recommendation I.412 (1988): "ISDN user-network interfaces - Interface
structures and access capabilities".
[4] CCITT Recommendation Q.512 (1988): "Exchange interfaces for subscriber
access".
[5] CCITT Recommendation G.821 (1988): "Error performance of an international
digital connection forming part of an integrated services digital network".
[6] CCITT Recommendation G.823 (1988): "The control of jitter and wander within
digital networks which are based on the 2048 kbit/s hierarchy".
[7] CCITT Recommendation G.706 (1988): "Frame alignment and cyclic redundancy
check (CRC) procedures relating to basic frame structures defined in
Recommendation G.704".
[8] CCITT Recommendation G.703 (1988): "Physical/electrical characteristics of
hierarchical digital interfaces".

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ETS 300 233: May 1994
[9] CCITT Recommendation G.704 (1988): "Synchronous frame structures used at
primary and secondary hierarchical levels".
[10] CCITT Recommendation Q.940 (1988): "ISDN user-network interface protocol
for management - general aspects".
[11] CCITT Recommendation I.411 (1988): "ISDN user-network interfaces -
Reference configuration".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of this ETS, unless otherwise indicated, the term TE is used to indicate terminating layer
1 aspects of TE1, TA and NT2 functional groups.
When the term TE indicates terminating layer 1 aspects of TE1, then according to figure 2 of CCITT
Recommendation I.411 [11], the S and T reference points coincide.
In this ETS references to LT only concern the LT inside the access digital section.
3.2 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
AIS Alarm Indication Signal
AUXP AUXiliary Pattern
CRC-4 Cyclic Redundancy Check
DS Primary Rate Access Digital Section
ET Exchange Termination
ETS European Telecommunication Standard
ETSI European Telecommunications Standards Institute
FC4 Failure Condition
FE Function Element
μs micro second
HDLC High Level Data Link Control
ISDN Integrated Services Digital Network
LFA Loss of Frame Alignment
LOS Loss of Signal
LT Line Termination
NF Normal Frame
NOF Normal Operational Frames
NT Network Termination
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ETS 300 233: May 1994
PH Packet Handler
RAI Remote Alarm Indication
SIG Signal between LT and NT1
TE Terminal Equipment
4 Configuration and application
4.1 Configuration
Figure 1 below shows the boundaries of the access digital section in relation to the digital transmission
system definition.
The concept of the access digital section is used in order to allow a functional and procedural description
and a definition of the network requirements.
The concept of a digital transmission system is used in order to describe the characteristics of an
implementation, using a specific medium, in support of the access digital section.
Digital transmission
system
‡<˜˜˜˜˜˜˜˜˜˜˜˜>‡
�˜˜˜˜˜˜˜¿   �˜˜˜˜˜˜·  (NOTE 2) ˆ˜˜˜˜˜˜¿    �˜˜˜˜˜˜¿
‡    ‡   ‡   ‡       ‡   ‡    ‡   ‡
‡ TE  ˆ˜˜˜˜´˜· NT1 ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜· LT ˆ˜˜˜´˜˜˜· ET ‡
‡    ‡  ‡ ‡   ‡       ‡   ‡  ‡  ‡   ‡
‡    ‡   ‡   ‡       ‡   ‡    ‡   ‡
�˜˜˜˜˜˜˜�  T �˜˜˜˜˜˜�       �˜˜˜˜˜˜� V3  �˜˜˜˜˜˜�
reference point          reference point
‡   Primary Rate Access     ‡
‡    Digital Section (DS)   ‡
‡<˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜>‡
‡                 ‡

NOTE 1: From a functional point of view the information transferred via the reference points T and V3 are
different and, therefore, the digital section is not symmetrical.
NOTE 2: Digital transmission system refers to either a line system using metallic media or optical fibres or
to a radio system.
Figure 1: Access digital section and transmission system boundaries

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ETS 300 233: May 1994
T    Primary Rate Access Digital Section (DS)  V3
‡<˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜>‡
‡         (NOTE 1)             ‡
�˜˜˜¿ ‡ �˜˜˜¿                    �˜˜˜¿ ‡ �˜˜˜˜¿
‡  ‡ ‡ ‡  ‡                    ‡  ‡ ‡ ‡  ‡
‡NT2ˆ˜¯˜·NT1ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·LT ˆ˜¯˜·  ‡
‡  ‡ ‡ ‡  ‡                    ‡  ‡ ‡ ‡  ‡
�˜˜˜� ‡ �˜˜˜�                    �˜˜˜� ‡ ‡  ‡
‡  ‡
T       Digital access link         V3’‡  ‡
‡<˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜>‡ ‡  ‡
‡   Access  V3                 ‡ ‡  ‡
‡digital section ‡ One first order digital section ‡ ‡  ‡
‡<˜˜˜˜˜˜˜˜˜˜˜˜˜˜>‡<˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜>‡ ‡  ‡
�˜˜˜¿ ‡ �˜˜˜¿  �˜˜˜¿ ‡ �˜˜˜˜¿          �˜˜˜˜¿ ‡ ‡  ‡
‡  ‡ ‡ ‡  ‡  ‡  ‡ ‡ ‡Line‡          ‡Line‡ ‡ ‡  ‡
‡NT2ˆ˜¯˜·NT1ˆ˜˜˜˜·LT ˆ˜¯˜·  ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·  ˆ˜¯˜·  ‡
‡  ‡ ‡ ‡  ‡  ‡  ‡ ‡ ‡term‡          ‡term‡ ‡ ‡  ‡
�˜˜˜� ‡ �˜˜˜�  �˜˜˜� ‡ �˜˜˜˜�          �˜˜˜˜� ‡ ‡  ‡
‡  (NOTE 1)  ‡                 ‡ ‡  ‡
‡  ‡
T                         V3’‡  ‡
‡         Digital access link       ‡ ‡  ‡
‡<˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜>‡ ‡ ET ‡
‡        V3                 ‡ ‡  ‡
‡  Access   ‡     ‡ Digital link ‡     ‡ ‡  ‡
‡digital section ‡     ‡  G.921   ‡     ‡ ‡  ‡
‡<˜˜˜˜˜˜˜˜˜˜˜˜˜˜>‡     ‡<˜˜˜˜˜˜˜˜˜˜˜˜>‡     ‡ ‡  ‡
‡   (NOTE 1)  ‡     ‡  (NOTE 2) ‡     ‡ ‡  ‡
�˜˜˜¿ ‡ �˜˜˜¿  �˜˜˜¿ ‡ �˜˜˜˜˜¿ ‡       ‡ �˜˜˜˜˜¿ ‡ ‡  ‡
‡  ‡ ‡ ‡  ‡  ‡  ‡ ‡ ‡   ‡ ‡       ‡ ‡   ‡ ‡ ‡  ‡
‡NT2ˆ˜¯˜·NT1ˆ˜˜˜˜·LT ˆ˜¯˜·   ‡ ‡       ‡ ‡   ‡ ‡ ‡  ‡
‡  ‡ ‡ ‡  ‡  ‡  ‡ ‡ ‡   ‡ ‡�˜˜˜˜¿ �˜˜˜˜¿‡ ‡   ˆ˜¯˜·  ‡
�˜˜˜� ‡ �˜˜˜�  �˜˜˜� ‡ ‡   ‡ ‡‡Line‡ ‡Line‡‡ ‡   ‡ ‡ ‡  ‡
‡        ‡ ‡ Mux ˆ˜¯·  ˆ˜˜·  ˆ¯˜· MUX ‡ ‡ ‡  ‡
�˜˜˜¿ ‡ �˜˜˜¿  �˜˜˜¿ ‡ ‡   ‡ ‡‡term‡ ‡term‡‡ ‡   ‡ ‡ ‡  ‡
‡  ‡ ‡ ‡  ‡  ‡  ‡ ‡ ‡   ‡ ‡�˜˜˜˜� �˜˜˜˜�‡ ‡   ‡ ‡ ‡  ‡
‡NT2ˆ˜¯˜·NT1ˆ˜˜˜˜·LT ˆ˜¯˜·   ‡         ‡   ˆ˜¯˜·  ‡
‡  ‡ ‡ ‡  ‡  ‡  ‡ ‡ ‡   ‡         ‡   ‡ ‡ ‡  ‡
�˜˜˜� ‡ �˜˜˜�  �˜˜˜� ‡ ‡   ‡         ‡   ‡ ‡ ‡  ‡
‡        ‡ �˜˜˜˜˜�         �˜˜˜˜˜� ‡ �˜˜˜˜�
(NOTE 3)
NOTE 1: The access digital sections may include one or more regenerators.
NOTE 2: Multiple applications of digital links and multiplexors may be possible, but see also subclause
7.2 "Jitter at the V3 reference point".
NOTE 3: In the case of remote access, the digital access link is terminated at the ET by a V3' reference
point which is functionally and electrically identical with the V3 reference point in the case of the
direct access.
NOTE 4: The Line Terminations (LTs) forming part of the first order digital section or the digital link are
outside the scope of this ETS.
Figure 2: Examples of equipment configurations in the ISDN primary rate access

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ETS 300 233: May 1994
4.2 Application
The Primary Rate Access Digital Section (DS) may be applied as given in figure 2 for:
- direct access to the local exchange;
- remote access via one first order digital section or via higher order multiplex equipment forming a
digital access link to the local exchange.
4.3 Modelling and relationship between the access digital section and the ET
The general model, as shown in figure 3, depicts the whole ISDN customer access layer 1 and adjacent
entities. It also provides the basis to describe the functions performed by the access digital section and
those performed by TE, ET and system management and how various functions are grouped. In particular,
according to this model, the maintenance functions specified in this ETS are not confined to functions
performed by the access digital section but include functions associated with ET layer 1.
This model includes primitive procedures between ET layer 1, ET layer 2 and system management:
a) ETS 300 011 [1] and CCITT Recommendations Q.920/Q.921 interactions between ET layer 1 and
ET layer 2 and system management based on Packet Handler (PH) and MPH primitives,
respectively, as defined in ETS 300 011 [1]. These interactions are for the support of functions
specified in CCITT Recommendations Q.920 and Q.921;
b) interactions between ET layer 1 and system management for the support of functions associated
with the access digital section, based on MPH primitives.
The primitive procedures within TE comply with the specification according to ETS 300 011 [1].
This model does not constrain layer 1 arrangements between LT and NT1, nor the digital transmission
system technology.
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ETS 300 233: May 1994
PH-primitves
PH-primitves
according to
according to
ETS 300 011[1]
B-channels
B-channels
ETS 300 011 [1]
Function MPH-Primitives
SIGs
MPH-Primitives
SIGs
Elements according to
(NOTE 2)
(NOTE 2)
according to
(NOTE 2) ETS 300 011 [1]
ET
TE
ETS 300 011[1]
layer 1
layer 1
LT
NT1
Digital
MPH-Primitives
transmission
T
V3 associated with
system
(NOTE 1)
line system
Access digital section
NOTE 1: The digital transmission system refers to either a digital system using a metallic pair of wires, optical fibre or radio system.
NOTE 2: SIG, FE and primitives refer to an exchange of information. It does not imply any specific coding nor implementation. Some of these functions may be terminated
in the LT and do not pass the digital transmission system.
NOTE 3: The term system management corresponds to both system management and layer management as defined in CCITT Recommendation Q.940 [10].
Figure 3: General model of ISDN customer access layer 1 and adjacent entities
System management (NOTE 3)
TE
layer 2
ET
layer 2
System management (NOTE 3)
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ETS 300 233: May 1994
5 Functions
Figure 4 below shows the functions which shall be supported by the Primary Rate Access Digital Section.
Primary Rate Access
T reference point   Digital Section    V3 reference point
�------------¿
<-----------> ‡B-, H0- or H1-channels ‡ <----------->
ˆ------------·
<-----------> ‡D-channel        ‡ <----------->
ˆ------------·
<-----------> ‡Bit timing       ‡ <----------->
ˆ------------·
<-----------> ‡Octet timing      ‡ <----------->
ˆ------------·
<-----------> ‡Frame alignment     ‡ <----------->
ˆ------------·
<-----------> ‡CRC procedures     ‡ <----------->
ˆ------------·
<-----------> ‡M-channel        ‡ <----------->
ˆ------------·
-----------> ‡Power feeding (NOTE)  ‡
ˆ------------·
<-----------> ‡Operation & Maintenance ‡ <----------->
�------------�
NOTE: This power-feed-function is optional and depends on the transmission medium used. Only the
NT1 may be powered from the interface at the T reference point (see ETS 300 011 [1]).
Figure 4: Functions supported in the access digital section
For each direction of transmission the following functions shall be provided:
- 30 timeslots at 64 kbit/s (numbered 1 to 15 and 17 to 31) for the transport of any appropriate
allocation of the B-, H0- and H1-channels;
- 1 timeslot at 64 kbit/s (numbered 16) for the transport of a D-channel;
- 1 timeslot at 64 kbit/s (numbered 0) for frame alignment, and to follow the procedures for multiframe
alignment, CRC-4 procedures and maintenance.
5.1 B-channel
This function provides for the bi-directional transmission of up to 30 independent B-channels, each having a
bit rate of 64 kbit/s as defined in CCITT Recommendation I.412 [3].
5.2 H0-channel
This function provides for the bi-directional transmission of up to 5 independent H0-channels, each having a
bit rate of 384 kbit/s as defined in CCITT Recommendation I.412 [3].
5.3 H1-channel
This function provides for the bi-directional transmission of one H1-channel having a bit rate of 1 920 kbit/s
as defined in CCITT Recommendation I.412 [3].
5.4 D-channel
This function provides for the bi-directional transmission of one D-channel at a bit rate of 64 kbit/s as
defined in CCITT Recommendation I.412 [3].

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ETS 300 233: May 1994
5.5 Bit timing
This function provides bit (signal element) timing to enable the TE, the access digital section or the ET to
recover information from the aggregate bit stream.
5.6 Octet timing
This function provides 8 kHz timing towards to the TE, the access digital section or the ET to enable voice
codecs to recover an octet structure and for other timing purposes as required.
5.7 Frame alignment
This function provides information to enable the TE, the access digital section or the ET to recover the
time-division multiplexed channels.
5.8 CRC-4 procedure
This function provides protection against false framing and for error performance monitoring of the access
digital section. The CRC-4 procedure shall be implemented according to ETR 001 [2], Option 2. This
includes the multiframe procedure defined in CCITT Recommendation G.704 [9].
5.9 M-channel
This function provides a bi-directional 4 kbit/s data channel for the implementation of management features
between ET and TE which is transparently transported in Sa4-bit of timeslot 0.
5.10 Power feeding
This optional function provides for remote feeding of the NT1 via the user-network interface as specified in
ETS 300 011 [1].
5.11 Operation and maintenance of the access digital section
This function supports actions and information required for control of the operation and maintenance of the
access digital section controlled by the ET as defined in ETR 001 [2], and utilises Sa5- and Sa6-bit as
defined in subclause 9.3.
The following categories of functions have been identified:
- commands regarding LT or NT1;
- information from LT or NT1;
- indications of defect conditions.
NOTE: The control of possible regenerators and additional maintenance functions concerning
the transmission system is outside the responsibility of the ET and is therefore not part
of the scope of this ETS, although it may be performed by the LT.
6 Signal transfer delay
The mean one way delay on the B-channels between the T and the V3 reference points shall not exceed
1 250 μs. In accordance with CCITT Recommendation G.114, this value is the mean of the propagation
times in the two directions of transmission.

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ETS 300 233: May 1994
7 Jitter
7.1 Output/input jitter at T reference point
The requirements shall be as specified in ETS 300 011 [1].
7.2 Jitter at the V3 reference point
The input jitter limits shall be as specified in CCITT Recommendation G.823 [6].
If the models shown in figure 2 are used to connect a customer to the ET, a jitter reducer shall not be
required at the V3 reference point.
8 Operation and maintenance
This Clause specifies the operation and maintenance functions.
It shall be possible to test and maintain the access digital section in accordance with ETR 001 [2] without
consideration of the subscriber's installation or procedures.
The operation and maintenance functions shall be based on the assumptions regarding the system
management given in Annex A (normative).
8.1 Control facilities
8.1.1 Loopbacks
8.1.1.1 Loopback implementation
The following loopbacks shall be implemented:
a) loopback 1 - a complete, transparent loopback located in the LT as specified in ETR 001 [2];
b) loopback 2 - a complete, transparent loopback located in the NT1 as specified in ETS 300 011 [1].
8.1.1.2 Loopback procedure
Loopbacks 1 and 2 shall be controlled by the ET.
A normal call set-up request shall not override a request for loopback 1 or 2.
The loopback shall be operated whenever the loopback command is detected regardless of the DS state.
A sequence of 8 consecutive codewords of loop command (as specified in Clause 9) shall be detected
before action is to be taken. Conversely, when the receipt of 8 consecutive loopback release commands
(as specified in Clause 9) or any other 8 consecutive signals with no loopback command have been
detected, the loopback shall be released.
8.2 Monitoring
8.2.1 Functions
The following operational conditions shall be monitored throughout the access digital section:
a) the defect conditions;
b) loss of power in the NT1;
c) transmission performance.
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ETS 300 233: May 1994
8.2.2 Defect conditions and consequent actions
8.2.2.1 Detection of defect conditions
The functional requirements for the maintenance of the access digital section are based on the provision of
functions in the ET and the TE as defined in the G and F state tables of ETS 300 011 [1].
The access digital section shall provide the means to transmit indications of detected defect conditions at
the interface at the T reference point in accordance with ETS 300 011 [1].
Defects detected by the access digital section shall be reported to the ET or the TE as appropriate.
8.2.2.2 Definition of defect indication signals
During normal operation of the DS and all failure conditions allowing the use of framed signals, except FC4,
the information in timeslots 1 to 31, the A-, Sa4-, Sa7- and Sa8-bit, pass transparently through the access
digital section; the frame and the multiframe alignment, the CRC-4 bits and the CRC error information (E-
bit) in both directions and the Sa5- and the Sa6-bit only towards the ET are generated in the NT1.
The following signals used to indicate defects are specified in ETS 300 011 [1], Clause 6, table 1:
- Normal Operational Frames (NOF);
- Remote Alarm Indication (RAI);
- Loss of Signal (LOS);
- Alarm Indication Signal (AIS).
The following additional signals are necessary to indicate defects in respect to the access digital section:
- Normal Frames (NF): these are frames without defect indications or loopback requests generated
by the ET or the TE, where the value of the A-bit, set to ONE or ZERO, is not relevant for the
access digital section;
- Frames: these are frames which may, in addition to the Normal Frames, contain in the Sa6-bits
defect indication signals generated in the NT1 and transmitted towards the ET or loopback requests
transmitted from the ET to the DS;
- Substituted Frames: these are frames generated by the NT1 in case of Loss of Signal (LOS) or
Loss of Frame Alignment (LFA) at the T reference point. The defect condition (FC 4) is indicated
towards the ET by means of Sa6-bits. The A-bit is set to ZERO. The Sa4-, Sa5-, Sa7- and Sa8-bits
as well as the bits of timeslots 1 to 31 containing the B-and D-channels are set to ONE;
- Loss of Frame Alignment (LFA);
- Loss of Power in the NT1 or LT;
- Auxiliary Pattern (AUXP): this is an unframed and continuous bitstream of alternating ONEs and
ZEROs (.10101010.) transmitted from the LT in both directions of transmission when Loss of
Signal (LOS) is detected at the corresponding receiver.

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ETS 300 233: May 1994
8.2.2.3 Detection of defect indication signals
The following conditions of the access digital section shall be detected and reported to the ET:
a) within the access digital section:
- LOS or LFA at line side of NT1;
- LOS at line side of LT;
- Loss of power at NT1 (if relevant);
- AIS at line side of NT1, which is generated in the network and passed transparently through
the LT.
b) at V3 reference point:
- LOS.
c) at T reference point:
- LOS or LFA;
- Loss of Power (if relevant).
8.2.2.4 Definition of detection algorithms
The detection algorithms of the signal are described as follows:
- Normal Operational Frames: the algorithm shall be in accordance with CCITT Recommendation
G.706 [7], subclauses 4.1.2 and 4.2;
- Loss of Frame Alignment (LFA): the algorithm shall be in accordance with CCITT Recommendation
G.706 [7], subclause 4.1.1;
- Loss of Signal (LOS) at the T and V3 reference point: the equipment shall assume "Loss of Signal"
when the incoming signal amplitude is, for a period of at least 1 ms, more than 20 dB below the
nominal output amplitude defined in CCITT Recommendation G.703 [8] for this interface.
This event shall also cause "Loss of Frame Alignment".
NOTE: The detection of LOS at the line side of NT1 and LT is implementation dependent and,
therefore, not subject to this ETS.
- AIS: AIS is detected when both of the two following conditions occur:
1) LFA; and
2) reception of 512 bit periods containing less than 3 binary ZEROs (reference is made to
CCITT Recommendation O.162, subclause 3.3.2);
- Loss of Power in the NT 1: the equipment shall assume "Loss of Power" when the voltage at the
input is below the minimum value defined in ETS 300 011 [1] and the operating condition of the NT1
cannot be maintained;
- Loss of Power in the LT: the equipment shall assume "Loss of Power" when the supply voltage is
below the value that is necessary to maintain the operating condition.

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ETS 300 233: May 1994
8.2.2.5 Consequent actions
When either:
- a defect condition has been detected, or
- a defect condition has disappeared, or
- a defect indication has been received, or
- a defect indication has disappeared,
the defect indication to the ET or to the TE shall be sent or removed with a maximum delay of 10 ms,
which shall not be interpreted as a guard time. The detection of a single event shall be reported.
8.3 Error performance monitoring
The NT1 in the access digital section shall support error performance monitoring by detecting CRC-4
blocks in error in the received signals, using the CRC-4 procedure specified in CCITT Recommendation
G.704 [9], subclause 2.3.3, and transmit CRC error information accordingly.
The access digital section shall indicate to the ET:
- CRC blocks in error detected at the line side of the NT1 by using the CRC error information which is
E-bit set to ZERO;
- CRC blocks in error detected at the T reference point of the NT1 by utilizing Sa6-bits as defined in
table 4 (optional);
- CRC error indication received from the TE in the E-bits by utilizing Sa6-bits as defined in table 4
(optional);
- CRC blocks in error detected at the T reference point of the NT1 and simultaneously received CRC
error information from the TE by utilising Sa6-bits as defined in table 4 (optional).
NOTE: Error performance evaluation in the ET is outside the scope of this ETS, but information
is given in Annex A, Clause A.3.
9 Operation and maintenance procedures
9.1 Partitioning of functions
ETS 300 011 [1] defines the network side of the user-network interface at reference point T as one
functional block which supports the operation and maintenance procedures across the T reference point
and the primitive procedures at the ET layer 1/ET layer 2 boundary and ET layer 1/system management
boundary. This block includes the functional groupings NT1, LT and ET layer 1.
This concept is described in terms of a state machine, referred to as the G state machine in
ETS 300 011 [1].
In order to describe the relationship between signals across the user-network interface at reference point
T, which are indicated as SIGNAL (SIG) in figure 3 of this ETS and defined in ETS 300 011 [1], and
signals across reference point V3, which are indicated as FUNCTION ELEMENT (FE) in figure 3 and
defined in subclause 9.3, and the relationship between these function elements and primitives, two state
machines are defined. One is in the access digital section (DS state machine), and the other on the
network side of the V3 reference point (ET layer 1 state machine). Figure 5 illustrates this approach.
In addition to primitives defined in ETS 300 011 [1] and ETS 300 125 related to basic call control, figure 5
also introduces a new set of primitives related to configuration control and the control of loopbacks.

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ETS 300 233: May 1994
Partitioning of operation and maintenance procedures between the two state machines is used for the
convenience of easy and accurate description. The ET layer 1 state machine is to be viewed as virtual, and
is not intended to imply any particular implementation, although the functional behaviour shall be as defined
in the ET state tables (see Annex A). It is required to interwork with the access digital section state
machine defined in this ETS and to satisfy the requirements specified in the G state table in
ETS 300 011 [1].
However, in order to implement a customer access, the DS state machine shall be partitioned further.
Figure 6 shows the partition of the DS state machine into an NT1 state machine (NT-states) and an LT
state machine (LT-states).
ETS
�˜˜˜˜˜˜˜˜˜˜˜˜˜¿   �˜˜˜˜˜˜˜˜¿300 011 [1]�˜˜˜˜˜˜˜˜˜˜˜˜˜˜¿
‡       ‡   ‡    ‡<˜˜˜˜˜˜˜˜˜>‡   ET    ‡
‡       ‡   ‡    ‡      ‡  layer 2  ‡
‡       ‡   ‡    ‡      �˜˜˜˜˜˜˜˜˜˜˜˜˜˜�
‡       ‡   ‡    ‡      �˜˜˜˜˜˜˜˜˜˜˜˜˜˜¿ \
‡       ‡   ‡    ‡  ETS  ‡�˜˜˜˜˜˜˜˜˜˜˜˜¿‡ ‡
T  ‡       ‡ V3 ‡  ET  ‡300 011 [1]‡‡ related to ‡‡ ‡
‡       ‡   ‡layer 1 ‡<˜˜˜˜˜˜˜˜˜>‡‡ call    ‡‡ ‡
‡  ‡       ‡ ‡ ‡    ‡      ‡‡ control  ‡‡ ‡
˜˜˜˜¯˜˜˜· DS state  ˆ˜˜¯˜˜·    ‡      ‡�˜˜˜˜˜˜˜˜˜˜˜˜�‡ ‡
‡  ‡  machine  ‡ ‡ ‡ state ‡      ‡�˜˜˜˜˜˜˜˜˜˜˜˜¿‡ ‡
<˜˜`˜> ‡       ‡<˜`˜>‡machine ‡additional ‡‡ related to ‡‡ ‡
SIGs ‡       ‡ FEs ‡    ‡<˜˜˜˜˜˜˜˜˜>‡‡ configura- ‡‡ ‡
‡       ‡   ‡    ‡      ‡‡tion control‡‡ ‡
‡       ‡   ‡    ‡      ‡�˜˜˜˜˜˜˜˜˜˜˜˜�‡ ‡
‡       ‡   ‡    ‡      ‡�˜˜˜˜˜˜˜˜˜˜˜˜¿‡ ‡
‡       ‡   ‡    ‡additional ‡‡ related to ‡‡ ‡
‡ (DS     ‡   ‡ (ET  ‡<˜˜˜˜˜˜˜˜˜>‡‡ loopback  ‡‡ ‡
‡ states)  ‡   ‡ states)‡      ‡‡ control  ‡‡ ‡
‡       ‡   ‡    ‡      ‡�˜˜˜˜˜˜˜˜˜˜˜˜�‡ ‡
�˜˜˜˜˜˜˜˜˜˜˜˜˜�   �˜˜˜˜˜˜˜˜�      �˜˜˜˜˜˜˜˜˜˜˜˜˜˜� /
Access
digital section
<˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜>
Figure 5: State machines
The NT1 state machine supports user-network interface procedures in accordance with ETS 300 011 [1]
based on signals and interacts with the LT state machine by means of a signal repertoire which shall be
supported by the digital transmission system. The LT state machine interacts with the ET layer 1 state
machine by means of a set of function elements. The ET layer 1 state machine contains those states which
represent the local exchange view of the status of the interface at reference point T and the digital section.
It supports the already specified primitive procedures to provide services to ET layer 2 and system
management in accordance with ETS 300 011 [1], and additional primitive procedures for the support of
functions associated with the access digital section.
This information is provided for the specification of the digital transmission system which is outside the
scope of this ETS.
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ETS 300 233: May 1994
‡    ‡      ‡      ‡
‡ ET  ‡      ‡ System  ‡
‡layer 2‡      ‡management ‡
‡    ‡      ‡      ‡
‡    ‡      ‡      ‡
‡    ‡      ‡      ‡
�´˜˜˜˜˜´�      ‡      ‡
P‡  P‡       ‡      ‡
H‡  H‡       ‡      ‡
|‡  |‡       ‡      ‡
A‡  D‡       ‡      ‡
I‡  I‡       ‡      ‡
�˜˜˜˜˜˜˜¿  �˜˜˜˜˜˜˜¿   �`˜˜˜˜˜`¿      ‡      ‡
‡    ‡  ‡    ‡   ‡    ‡ MPH-AI  ‡�˜˜˜˜˜˜˜˜˜¿‡
‡    ‡  ‡    ‡   ‡    ˆ˜˜˜˜˜˜˜˜˜˜˜˜>‡     ‡‡
‡    ‡  ‡    ‡   ‡ ET  ‡ MPH-DI  ‡‡     ‡‡
T  ‡ NT1 ‡  ‡ LT  ‡ V3 ‡layer1 ˆ˜˜˜˜˜˜˜˜˜˜˜˜>‡Operation‡‡
‡  ‡ state ‡  ‡ state ‡ ‡  ‡ state ‡ MPH-L.  ‡‡control ‡‡
‡  ‡machine‡  ‡machine‡ ‡  ‡machine<˜˜˜˜˜˜˜˜˜˜˜˜·‡procedure‡‡
        ‡  ‡    ‡  ‡    ‡Elems->    ˆ˜˜˜˜˜˜˜˜˜˜˜˜>‡     ‡‡
‡  ‡    ‡  ‡    ‡ ‡  ‡    ‡      ‡‡     ‡‡
‡  ‡ (NT  ‡  ‡ (LT  ‡ ‡  ‡ (ET  ‡      ‡�˜˜˜˜˜˜˜˜˜�‡
‡  ‡states)‡  ‡states)‡ ‡  ‡states)‡      ‡      ‡
‡  ‡    ‡  ‡    ‡ ‡  ‡    ‡      ‡      ‡
‡  �˜
...