ETSI ETS 300 011-1 ed.2 (1998-03)

SLOVENSKI STANDARD
01-december-2003
Digitalno omrežje z integriranimi storitvami (ISDN) – Primarni vmesnik uporabnik-
omrežje (UNI) – 1. del: Specifikacija prve plasti
Integrated Services Digital Network (ISDN); Primary rate User-Network Interface (UNI);
Part 1: Layer 1 specification
Ta slovenski standard je istoveten z: ETS 300 011-1 Edition 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.

EUROPEAN ETS 300 011-1
TELECOMMUNICATION March 1998
STANDARD Second Edition
Source: TM Reference: RE/TM-03037-1
ICS: 33.020
Key words: ISDN, layer 1, primary, rate, UNI, transmission
Integrated Services Digital Network (ISDN);
Primary rate User-Network Interface (UNI);
Part 1: Layer 1 specification
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.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 1998. All rights reserved.

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ETS 300 011-1: March 1998
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 300 011-1: March 1998
Contents
Foreword .7
1 Scope .9
2 Normative references.9
3 Definitions, symbols and abbreviations.10
3.1 Definitions .10
3.2 Symbols .12
3.3 Abbreviations .12
4 Type of configuration.12
4.1 Point-to-point.12
4.2 Location of interface .13
4.3 Interface wiring.13
4.4 Interface connector .13
5 Functional characteristics.14
5.1 Summary of functions (layer 1).14
5.2 Interchange circuits.15
5.3 Activation/deactivation .15
5.4 Definition of primitives.17
5.5 Frame structure .17
5.5.1 Number of bits per time slot .17
5.5.2 Number of timeslots per frame.17
5.5.3 Assignments of bits in time slot 0.17
5.5.4 Description of the CRC-4 procedure in bit 1 of the frame .18
5.5.4.1 Allocation of bit 1 to 8 of the frame for a complete
multiframe.18
5.5.4.2 Sub-Multiframe (SMF) .18
5.5.4.3 Use of bit 1 in 2 048 kbit/s CRC-4 multiframe .19
5.5.5 Cyclic Redundancy Check (CRC) .19
5.5.5.1 Multiplication/division process .19
5.5.5.2 Encoding procedure.19
5.5.5.3 Decoding procedure .19
5.6 Bit sequence independence.19
5.7 Line code .19
5.8 Timing considerations.20
6 Interface procedure .20
6.1 Definition of signals at the interface.20
6.2 Definitions of state tables at network and user sides.21
6.3 Layer 1 states on the user side of the interface.22
6.4 Layer 1 states at the network side of the interface .23
6.5 State tables.24
6.6 Allocation of time slots .26
6.7 Interframe (layer 2) time fill .26
6.8 Frame alignment and CRC-4 procedures.26
6.8.1 Loss and recovery of basic frame alignment.26
6.8.1.1 Loss of basic frame alignment.26
6.8.1.2 Strategy for basic frame alignment recovery .26
6.8.2 CRC multiframe alignment using information in bit 1 of the basic frame .26
6.8.3 CRC bit monitoring.27
6.8.3.1 Monitoring procedure.27
6.8.3.2 Monitoring for false basic frame alignment.27
6.8.3.3 Error performance monitoring using CRC-4.28

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ETS 300 011-1: March 1998
7 Maintenance at the interface . 28
7.1 Definitions of maintenance signals. 29
7.2 Use of CRC procedure. 29
7.2.1 Introduction . 29
7.2.2 Localization of the CRC functions from the user point of view . 29
7.2.2.1 No CRC processing in the transmission link. 29
7.2.2.2 CRC processing in the digital transmission link. 30
7.3 Maintenance functions . 30
7.3.1 General requirements. 30
7.3.2 Maintenance functions on the user side . 31
7.3.2.1 Anomalies and defect detection. 31
7.3.2.2 Detection of defect indication signals. 31
7.3.2.3 Consequent actions . 31
7.3.3 Maintenance functions on the network side. 32
7.3.3.1 Defect detection . 32
7.3.3.2 Detection of defect indication signals. 32
7.3.3.3 Consequent actions . 32
8 Electrical characteristics . 33
8.1 Type of interface. 33
8.2 Specifications at the output ports . 33
8.2.1 Bit rate . 33
8.2.2 Waveform shape . 33
8.2.3 Return loss at the output port . 35
8.2.4 Impedance towards ground of the output port. 35
8.3 Specification at the input ports . 35
8.3.1 Receiver sensitivity . 35
8.3.2 Return loss at the input port. 35
8.3.3 Input port immunity against reflections . 35
8.3.4 Tolerable longitudinal voltage . 36
8.3.5 Impedance towards ground of the input port . 36
8.4 Jitter. 36
8.4.1 General considerations. 36
8.4.2 Minimum tolerance to jitter and wander at TE inputs . 37
8.4.2.1 Tolerable input jitter when connected at T, S or S/T
reference point . 37
8.4.2.2 Tolerable input jitter when connected to leased lines . 38
8.4.3 TE and NT2 output jitter at interface I . 38
A
8.4.3.1 TE and NT2 with only one UNI. 38
8.4.3.2 TE and NT2 with more than one UNI to the same public
ISDN. 39
8.4.3.3 TE and NT2 designed for interconnection via leased lines. 39
8.4.4 Minimum tolerance to jitter and wander at NT inputs . 39
8.4.4.1 Tolerable input jitter at T reference point . 39
8.4.4.2 Tolerable input jitter at leased lines input. 40
9 Power feeding. 40
9.1 Provision of power. 40
9.2 Power available at the NT . 40
9.3 Feeding voltage. 41
9.4 Safety requirements .41
Annex A (normative): Application of ETS 300 011-1 to the S reference point. 42
A.1 Scope. 42
A.2 Requirements . 42
A.2.1 Timing considerations . 42
A.2.2 Jitter, general considerations . 42
A.2.3 Frame alignment and CRC-4 procedures . 42
A.3 Interface wiring . 43

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ETS 300 011-1: March 1998
A.4 Loopbacks required at S reference point .43
Annex B (normative): Characteristics of loopbacks .44
B.1 Introduction.44
B.2 Characteristics of loopback at the network side.44
B.3 Characteristics of loopbacks for primary rate customer installations.45
Annex C (informative): Overview of technical changes to edition 1 .46
Annex D (informative): Bibliography.47
History.48

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ETS 300 011-1: March 1998
Foreword
This second edition European Telecommunication Standard (ETS) was produced by the Transmission
and Multiplexing (TM) Technical Committee of the European Telecommunications Standards Institute
(ETSI).
This ETS aims to meet urgent requirements of network operators and equipment manufacturers who are
designing equipment to operate with an Integrated Services Digital Network (ISDN) primary rate access
User Network Interface (UNI).
This ETS is based upon CCITT Recommendation I.431 and provides modifications and further
requirements to that document. It also is affected by CCITT Recommendations G.703, G.704 and G.706,
and modifications to these CCITT Recommendations are provided within this ETS.
This ETS also takes into account requirements contained in ECMA Standard 104: "Physical layer at the
primary rate access interface between data processing equipment and private switching networks (1985)",
which are given in annex A.
This ETS consists of 3 parts as follows:
Part 1: "Layer 1 specification";
Part 2: "Conformance test specification for interface I and I ";
A B
Part 3: "Implementation Conformance Statement (ICS) and Implementation eXtra Information for Testing
(IXIT) proforma specification for lnterface I and I ".
A B
Transposition dates
Date of adoption of this ETS: 6 March 1998
Date of latest announcement of this ETS (doa): 30 June 1998
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 December 1998
Date of withdrawal of any conflicting National Standard (dow): 31 December 1998

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ETS 300 011-1: March 1998
1 Scope
This second edition European Telecommunication Standard (ETS) specifies requirements and test
principles for the ISDN 2 048 kbit/s primary rate UNI including the physical, electrical and functional
characteristics and the information exchange with higher layers. Compliance with this ETS ensures that,
with regard to layer 1 interface aspects, equipment for use with ISDN primary rate access is portable
within countries that adhere to this ETS and, furthermore, that interworking with higher layer protocols for
ISDN is supported.
This ETS is applicable to equipment having interface I or I for the connection to the ISDN primary rate
A B
UNI intended to be installed on customers' premises. In accordance with CCITT
Recommendation I.411 [1], this ETS is to be applied to interfaces at reference points S, T and S/T
(coincident S and T) of the ISDN reference configuration.
This ETS is applicable for ISDN channel arrangements as defined in CCITT Recommendation I.412 [2],
as far as the primary rate at 2 048 kbit/s is concerned.
Annex A specifies additional requirements for interfaces at reference point S.
This ETS does not specify:
- safety requirements;
- interface or equipment overvoltage protection requirements;
- immunity requirements against electromagnetic interferences;
- emission limitation requirements.
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
applies to this ETS only when incorporated in it by amendments or revision. For undated references the
latest edition of the publication referred to applies.
[1] CCITT Recommendation I.411 (1993): "ISDN user-network interfaces -
Reference configurations".
[2] CCITT Recommendation I.412 (1988): "ISDN user-network interfaces- Interface
structures and access capabilities".
[3] CCITT Recommendation O.151 (1992): "Error performance measuring
equipment operating at the primary rate and above".
[4] EN 60950 (1992): "Safety of information technology equipment including
electrically operated business machines".
[5] EN 60603-7 (1993): "Connectors for frequencies below 3 MHz for use with
printed boards - Part 7: Detail specification for connectors, 8-way, including fixed
and free connectors with common mating features".
[6] EN 50082-1 (1992): "Electromagnetic compatibility - Generic immunity standard
- Part 1: Residential, commercial and light industry".
[7] CCITT Recommendation O.162 (1992): "Equipment to perform in-service
monitoring on 2048, 8448, 34 368 and 139 264 kbit/s signals".
[8] ITU-T Recommendation M.20: "Maintenance philosophy for telecommunication
networks".
[9] ETR 001: "Integrated Services Digital Network (ISDN); Customer access
maintenance".
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ETS 300 011-1: March 1998
[10] ETS 300 046-2 (1992): "Integrated Services Digital Network (ISDN); Primary
rate access - safety and protection Part 2 : Interface I - safety".
A
[11] ETS 300 046-3 (1992): "Integrated Services Digital Network (ISDN); Primary
rate access - safety and protection, Part 3: Interface I - protection".
A
[12] ETS 300 046-4 (1992): "Integrated Services Digital Network (ISDN); Primary
rate access - safety and protection, Part 4: Interface I - safety".
B
[13] ETS 300 046-5 (1992): "Integrated Services Digital Network (ISDN); Primary
rate access - safety and protection, Part 5: Interface I - protection".
B
[14] ETS 300 125 (1991): "Integrated Services Digital Network (ISDN); User-network
interface data link layer specification Application of CCITT Recommendations
Q.920/I.440 and Q.921/I.441".
[15] ETS 300 166 (1993): "Transmission and Multiplexing (TM); Physical and
electrical characteristics of hierarchical digital interfaces for equipment using the
2048 kbit/s -based plesiochronous or synchronous digital hierarchies".
[16] ETS 300 233 (1994): "Integrated Services Digital Network (ISDN); Access digital
section for ISDN primary rate".
[17] ETS 300 247 (1995): "Business Telecommunications (BT); Open Network
Provision (ONP) technical requirements; 2 048 kbit/s digital unstructured leased
line (D2048U) Connection characteristics".
[18] ETS 300 419 (1995): "Business TeleCommunications (BTC); 2 048 kbit/s digital
structured leased lines (D2048S); Connection characteristics".
[19] CCITT Recommendation X.200 (1994): "Information technology - Open
Systems Interconnection - Basic reference model: The basic model".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of this ETS, the following definitions apply:
Alternate Mark Inversion (AMI): Is a code where ONEs are represented by alternate positive and
negative pulses, and ZEROs by spaces.
High-Density Bipolar 3 (HDB3): Is a modified AMI code. An exception occurs for blocks of 4 successive
ZEROs. Each block of 4 successive ZEROs is replaced by OOOV or BOOV where B represents an
inserted pulse conforming to the AMI and V represents an AMI violation. The choice of OOOV or BOOV is
made so that the number of B pulses between consecutive V pulses is odd. In other words, successive V
pulses are of alternate polarity so that no direct current (dc) component is introduced.
interface I : User side of the ISDN UNI for the primary rate access.
A
interface I : Network side of the ISDN UNI for the primary rate access.
B
network side: NT1, LT and ET functional groups in case of an interface at the T reference point; or
relevant parts of the NT2 functional group in case of an interface at the S reference point.
network option 1: The digital link between interface at the T and V reference point does not provide a
CRC-4 processing, i.e. the CRC-4 is terminated in the TE and the ET. This digital link is called to be
"without CRC processing" (see subclause 7.2.2.2).
NOTE 1: This option is not provided by the public ISDN at the T reference point. However it
might be used for Private Telecommunications Network Exchange (PTNX)
interconnection using unstructured 2 048 kbit/s leased lines.

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ETS 300 011-1: March 1998
network option 2: The digital link between interface at the T and V reference point provides CRC-4
processing in the NT1 and the ET according ETR 001 [9]. Therefore the combinations of CRC-4 error
information and Remote Alarm Indication (RAI) indicate the fault condition; FC1 or FC4
(see subclause 7.2.2.1).
NOTE 2: Option 3 of CCITT Recommendation I.604 with CRC-4 processing in NT1, LT and ET
is not relevant for this ETS.
Network Termination (NT): An equipment providing interface I .
B
NOTE 3: This term is used in this ETS to indicate network-terminating aspects of NT1 and NT2
functional groups where these have an I interface.
B
Network Termination Type 1 (NT1): This functional group includes functions broadly equivalent to layer
1 (physical) of the Open System Interconnection (OSI) reference model. These functions are associated
with the proper physical and electromagnetic termination of the network. NT1 functions are:
- line transmission termination;
- layer 1 maintenance functions and performance monitoring;
- timing;
- layer 1 multiplexing;
- interface termination.
Network Termination Type 2 (NT2): This functional group includes functions broadly equivalent to layer
1 and higher layers of the CCITT Recommendation X.200 [19] reference model. Private
Telecommunication Network Exchanges (PTNXs), local area networks and terminal controllers are
examples of equipment or combinations of equipment that provide NT2 functions. NT2 functions include:
- layer 2 and layer 3 protocol handling;
- layer 2 and layer 3 multiplexing;
- switching;
- concentration;
- maintenance functions;
- interface termination and other layer 1 functions.
Private Telecommunication Network Exchange (PTNX): A nodal identity in a private
telecommunication network which provides autonomous and automatic switching and call handling
functions used for the provision of telecommunication services which are based on the definitions for
those of the public ISDN.
Private Network Termination (PNT): A remote unit of equipment which terminates a transmission
system employed between the PTNX and the interface I and the S reference point.
B
Terminal Adapter (TA): An equipment with interface I and one or more auxiliary interfaces that allow
A
non-ISDN terminals to be served by an ISDN UNI.
Terminal Equipment (TE): An equipment providing an interface I .
A
NOTE 4: This term is used in this ETS to indicate terminal-terminating layer 1 aspects of TE1,
TA and NT2 functional groups, where these have an I interface.
A
NOTE 5: In annex A, this definition applies with the exception that the NT2 functional grouping is
not covered.
Terminal Equipment Type 1 (TE1): This functional group includes functions belonging to the functional
group TE, and with an interface that complies with the ISDN UNI standard.
user side: Terminal terminating layer 1 aspects of TE1, TA and NT2 functional groups.

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ETS 300 011-1: March 1998
3.2 Symbols
For the purposes of this ETS, the following symbols apply:
ONE binary "1"
ZERO binary "0"
3.3 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
AIS Alarm Indication Signal
AMI Alternate Mark Inversion
CRC Cyclic Redundancy Check
dc direct current
EMC ElectroMagnetic Compatibility
ET Exchange Termination
FC Fault Condition
HDB3 High-Density Bipolar 3 (line code)
ISDN Integrated Service Digital Network
LOS Loss Of Signal
MPH Management (entity) - PHysical (layer) [primitive]
MPH-Al MPH Activate Indication
MPH-El MPH Error Indication
MTIE Maximum Time Interval Error
NOF Normal Operational Frames
NT Network Termination
PH PHysical (layer)
PH-Al PH - Activate Indication
PH-Dl PH - Deactivate Indication
PNT Private Network Termination
PRBS Pseudo-Random Binary Sequence
PTN Private Telecommunications Network
PTNX Private Telecommunications Network Exchange
RAI Remote Alarm Indication
SMF Sub-MultiFrame
TA Terminal Adapter
TE Terminal Equipment
UNI User Network Interface
4 Type of configuration
The type of configuration applies only to the layer 1 characteristics of the interface and does not imply any
constraints on modes of operation at higher layers.
4.1 Point-to-point
The primary rate shall support only the point-to-point configuration.
Point-to-point configuration at layer 1 implies that for each direction only one source (transmitter) and one
sink (receiver) are connected to the interface. The maximum reach of the interface in the point-to-point
configuration is limited by specification for the electrical characteristics of transmitted and received pulses
and the type of interconnecting cable.

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4.2 Location of interface
The electrical characteristics apply to the interface points I and I of figure 1.
A B
TE NT
I
I B
A
NOTE: I is located at the input and output ports of the TE. I is located at the input and output ports of
A B
the NT.
Figure 1: Location of interfaces
4.3 Interface wiring
The magnitude of the characteristic impedance of symmetrical type interface cable shall be 120 W – 20 %
in a frequency range from 200 kHz to 1 MHz and 120 W – 10 % at 1 MHz.
The use of shielded interface cables may be required to meet radiation emission and immunity
requirements. Therefore the Terminal Equipment (TE) and the Network Termination (NT) shall have
provided a point on the equipment where a shield of the interface cable can, and if provided shall be
connected to.
This point shall be designed respecting EMC requirements providing access to the signal reference for the
transmitter and receiver of the equipment interface.
Application of interface cable with individually shielded pairs or with a common shield for both pairs shall
be possible.
4.4 Interface connector
The interface connector and contact assignments is specified in EN 60603-7 [5] and the contact
assignments in table 1. However permanent wiring connections from TE to NT are also permitted.

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ETS 300 011-1: March 1998
Table 1: contact assignments
Contact Network interface
1 & 2 Transmit pair
3 Unused
4 & 5 Received pair
6 Unused
7 Unused
8 Unused
NOTE: The transmit pair is the output from the network
interface. The receive pair is the input to the
network interface
5 Functional characteristics
5.1 Summary of functions (layer 1)
TE NT
B-, H0- or H1-channels <---> B-, H0- or H1-channels
1 D-channel 64 kbit/s 1 D-channel 64 kbit/s
<--->
Bit timing <---> Bit timing
Octet timing Octet timing
<--->
Frame alignment <---> Frame alignment
Power feeding ----> Power feeding
Maintenance Maintenance
<--->
CRC procedure <---> CRC procedure
NOTE: This power feeding function uses a separate pair of wires.
Figure 2: Functional characteristics
B-channel: This function shall provide for the bi-directional transmission of independent B-channel
signals each having a bit rate of 64 kbit/s. A B-channel may be assigned to any time slot, except time slots
0 and 16.
D-channel: This function shall provide for the bi-directional transmission of one D-channel signal at a bit
rate of 64 kbit/s. The D-channel shall be assigned to time slot 16.
H0-Channel: This function shall provide for the bi-directional transmission of up to 5 independent H0
signal, each having a bit rate of 384 kbit/s. A H0-channel may be assigned to any 6 time slots, except time
slots 0 and 16.
H1-channel: This function shall provide for the bi-directional transmission of 1 H1 channel having a bit
rate of 1 920 kbit/s. A H1-channel shall be assigned to time slots 1 to 15 and 17 to 31.
Bit riming: This function shall provide bit (signal element) timing to enable the TE or NT to recover
information from the aggregate bit stream.
Octet timing: This function shall provide 8 kHz timing towards TE or NT for the purpose of supporting an
octet structure for voice coders and for other timing purposes as required.
Frame alignment: This function shall provide information to enable the TE or NT to recover the
time-division multiplexed channels. Time slot 0 shall provide the frame alignment in accordance with
subclause 6.8.1.
Power feeding: This function shall provide for the capability to transfer power across the interface
towards the NT1.
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ETS 300 011-1: March 1998
Maintenance: This function shall provide information concerning operational or failure conditions of the
interface. The network reference configuration for maintenance activities on primary rate subscriber
access is given in ETR 001 [9].
Cyclic Redundancy Check (CRC)-4 procedure: This function shall provide for the protection against
false framing and may provide for error performance monitoring of the interface.
5.2 Interchange circuits
Two interchange circuits, one for each direction, shall be used for the transmission of digital signals. All
the functions listed above, with the exception of power feeding and possibly maintenance, are combined
into two composite digital signals, one for each direction of transmission.
If power feeding via the interface is provided, an additional interchange circuit shall be used for power
feeding.
The two wires of the pairs carrying the digital signal may be reversed.
5.3 Activation/deactivation
The interfaces for the primary rate UNI shall be active at all times. No activation/deactivation procedures
shall be applied at the interface. However, for consistency in the layer model between primary rate and
basic rate the same set of primitives shall be used. The exchange of these primitives and state changes
are illustrated in figure 3.
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ETS 300 011-1: March 1998
Information
PH-DI
PH-AR transfer
not available
PH-AI
PH-DI
Information
transfer
PH- DATA
available
request
PH-DATA
PH-AI
indication
a) Layer 1 - Layer 2
Information
MPH-DI
transfer
MPH-EI
not available
MPH-AI
MPH-DI
Information
transfer
MPH-AI
available
b) Layer 1 - Management; User side
MPH-AI
MPH-DI
MPH-EI
MPH- LxAR
Information
Information transfer
transfer
MPH-EI
not available,
not available
maintenance
MPH-DR
MPH-AI
MPH-DI
Information
transfer
MPH-AI
available
c) Layer 1 - Management; Network side
NOTE: All possible transitions are shown; refer to ETS 300 233 [16] for further information about
maintenance procedures.
Figure 3: Exchange of primitives

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5.4 Definition of primitives
The primitives given in table 2 shall be used between layers 1 and 2 and between layer 1 and the
management entity.
Table 2: Physical layer primitives
Specific name Parameter Parameter data content
REQUEST INDICATION Priority Parameter
indicator data
Layer 1 <-> Layer 2
PH-DATA U/N U/N X X DL-PDU
(see
note 2)
PH-ACTIVATE U/N U/N - -
(see note 3)
PH-DEACTIVATE - U/N - -
Layer 1 <-> Management
MPH-ERROR - U/N - X Type of error
MPH-ACTIVATE - U/N - -
MPH-DEACTIVATE N U/N - -
(see note 4)
MPH-LxACTIVATE N - - X Loopback indicator
(see note 1)
U = Exists at user side; N = Exists at network side; X = Exists; - = Does not exist
NOTE 1: This is used in association with access digital section functions within the network side,
see ETS 300 233 [16].
NOTE 2: Priority indicator applies only to the request type. The priority indicator shall be used to
give priority to information belonging to priority class 1 if queues for DL-PDUs are
implemented at layer 1.
NOTE 3: This primitive is given for consistency with layer 2 but not used in the layer 1 interface
status procedures because the procedures are defined for permanent layer 1 activation.
NOTE 4: This primitive is to request a loopback release within the network side which was invoked
by an MPH-LxACTIVATE, refer to ETS 300 233 [16].
5.5 Frame structure
5.5.1 Number of bits per time slot
A time slot shall consist of eight bits, numbered from 1 to 8.
5.5.2 Number of timeslots per frame
A frame shall consist of thirty-two time slots, numbered from 0 to 31. The number of bits per frame is 256
and the frame repetition rate is 8 000 frames/s.
5.5.3 Assignments of bits in time slot 0
Bits 1 to 8 of the frame (time slot 0) shall be as shown table 3.

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ETS 300 011-1: March 1998
Table 3: Allocation of bits 1 to 8 of the frame
1 234 56 78
Bit
number
Alternate frames
Frame containing the S 001 10 11
i
frame alignment signal Frame alignment signal
Frame not containing the S 1A S S S S S
i a4 a5 a6 a7 a8
frame alignment signal (see (see (see (see note 4)
note 1) note 2) note 3)
NOTE 1: S bits are used for CRC-4 multiframe.
i
NOTE 2: This bit is fixed at ONE to assist in avoiding simulations of the frame alignment signal.
NOTE 3: A = RAI. In undisturbed operation, set to ZERO; in alarm condition (RAI), set to ONE.
NOTE 4: Bits S to S shall be set to ONE by TEs. S and S are reserved for international
a4 a8 a4 a8
standardization S to S are reserved for national use. TEs shall ignore any received
a5 a7
pattern.
5.5.4 Description of the CRC-4 procedure in bit 1 of the frame
5.5.4.1 Allocation of bit 1 to 8 of the frame for a complete multiframe
The allocation of bits 1 to 8 of the frame is shown in table 4 for a complete CRC-4 multiframe.
Table 4: CRC-4 multiframe structure
Sub-multiframe Frame Bits 1 to 8 of the frame
(SMF) number 1 2345 678
0C 0011 011
101AS S S S S
a4 a5 a6 a47 a8
2C 0011 011
13 01AS S S S S
a4 a5 a6 a47 a8
4C 0011 011
511AS S S S S
a4 a5 a6 a47 a8
6C 0011 011
Multi- 7 0 1 A S S S S S
a4 a5 a6 a47 a8
frame 8 C 0011 011
911AS S S S S
a4 a5 a6 a47 a8
10 C 0011 011
211 11AS S S S S
a4 a5 a6 a47 a8
12 C 0011 011
13 E 1 A S S S S S
a4 a5 a6 a47 a8
14 C 0011 011
15 E 1 A S S S S S
a4 a5 a6 a47 a8
NOTE 1: E = CRC-4 error indication bits (see subclause 5.5.4.3).
SMF (block) with error: E = ZERO, SMF (block) without error: E = ONE.
NOTE 2: S to S = Spare bits (see note 4 to table 3).
a4 a8
NOTE 3: C to C = CRC-4 bits (see subclause 5.5.5).
1 4
NOTE 4: A = RAI (see table 3).
5.5.4.2 Sub-Multiframe (SMF)
Each CRC-4 multiframe, which is composed of 16 frames numbered 0 to 15, is divided into two 8-frame
sub-multiframes, designated SMF 1 and SMF 2 which signifies their respective order of occurrence within
the CRC-4 multiframe structure. The SMF is the CRC-4 block size (i.e. 2 048 bits).

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5.5.4.3 Use of bit 1 in 2 048 kbit/s CRC-4 multiframe
In those frames containing the frame alignment signal (defined in subclause 5.5.3) bit 1 is used to transmit
the CRC-4 bits. There are four CRC-4 bits, designated C , C , C , and C in each SMF.
1 2 3 4
In those frames not containing the frame alignment signal (see subclause 5.5.3), bit 1 is used to transmit
the 6-bit CRC-4 multiframe alignment signal and two CRC-4 error indication bits (E).
The CRC multiframe alignment signal has the form "001011".
The E-bits shall be used to indicate received errored sub-multiframes by setting the binary state of one
E-bit from ONE to ZERO for each errored sub-multiframe. Any delay between the detection of an errored
sub-multiframe and the setting of the E-bit that indicates the error state shall be less than 1 second.
The E-bits shall always be taken into account even if the SMF which contains them is found to be errored,
since there is little likelihood that the E-bits themselves will be errored.
5.5.5 Cyclic Redundancy Check (CRC)
5.5.5.1 Multiplication/division process
A particular CRC-4 word, located in sub-multiframe N, is the remainder after multiplication by x and then
division (modulo 2) by the generator polynomial x + x + 1, of the polynomial representation of
sub-multiframe N - 1.
When representing the contents of the check block as a polynomial, the first bit in the block, i.e. frame 0,
bit 1 or frame 8, bit 1, shall be taken as being the most significant bit. Similarly, C is defined to be the
most significant bit of the remainder and C the least significant bit of the remainder.
5.5.5.2 Encoding procedure
a) The CRC-4 bits in the SMF are replaced by ZEROs;
b) the SMF is then acted upon by the multiplication/division process referred to in subclause 5.5.5.1;
c) the remainder resulting from the multiplication/division process is stored, ready for insertion into the
respective CRC-4 locations of the next SMF.
NOTE: The CRC-4 bits thus generated do not affect the result of the multiplication/division
process in the next SMF because, as indicated in a) above, the CRC-4 bit positions in
an SMF are initially set to ZERO during the multiplication/division process.
5.5.5.3 Decoding procedure
a) A received SMF is acted upon by the multiplication/division process referred to in subclause 5.5.5.1,
after having its CRC-4 bits extracted and replaced by ZEROs;
b) the remainder resulting from this division process is then stored and subsequently compared on a
bit-by-bit basis with the CRC bits received in the next SMF;
c) if the remainder calculated in the decoder exactly corresponds to the CRC-4 bits received in the
next SMF, it is assumed that the checked SMF is error free.
5.6 Bit sequence independence
Interface I shall provide bit sequence independent transmission in time slots 1 to 31.
B
5.7 Line code
The line code shall be High-Density Bipolar 3 (HDB3).

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5.8 Timing considerations
The NT shall derive its timing from the network clock. The TE shall synchronize its timing (bit, octet,
framing) from the signal received from the NT and shall synchronize accordingly the transmitted signal.
In an unsynchronized condition (e.g. when the access that normally provides network timing is
unavailable) the frequency deviation of the free-running clock shall not exceed – 50 ppm.
Any TE which provides more than one interface is declared to be a multiple access TE and shall be
capable of taking the synchronizing clock frequency for its internal clock generator from more than one
access (or all access links) and synchronize the transmitted signals at each interface accordingly.
A TE (PTNX) which is designed to act as a synchronization master in a private network application shall
have a clock accuracy better than – 32 ppm.
A Private Telecommunications Network Exchange (PTNX) with a high clock accuracy class of better than
– 1 ppm may not be able to synchronize its internal clock to an input frequency with a tolerance of
– 32 ppm. The timing negotiation function being specified for private networks shall guarantee that the
PTNX with the higher clock accuracy shall act as the master after re-establishment of the configuration.
A TE which is designed to be connected to the T reference point only or a TE with a free running clock
accuracy better than – 1 ppm, shall be able to synchronize at the nominal bit rate – 1 ppm. Other TEs
shall be able to synchronize at the nominal bit rate – 32 ppm.
In order to limit the impact on the service performance following the loss of synchronization, the maximum
time for resynchronization to the network clock shall be less than 30 s, with the frequency deviation
applied to the input port limited to – 1 ppm.
6 Interface procedure
6.1 Definition of signals at the interface
Signals exchanged between the network and user side under normal and fault conditions are listed in
table 5. Further information on these signals is given in subclause 7.1.
The detection algorithm for signals given in table 5 and others is defined as follows:
- normal operational frames: the algorithm shall be in accordance with subclauses 6.8.1.2 and 6.8.2;
- loss of frame alignment: the algorithm shall be in accordance with subclause 6.8.1.1;
- RAI: this is detected when both of the two following conditions occur:
- frame alignment condition;
- reception of one bit A set to ONE.
- Loss Of Signal (LOS): the equipment shall assume loss of signal when the incoming signal
amplitude is more than 20 dB below the nominal output amplitude for this interface for more than
1 ms;
NOTE: The detection of this event is necessary if an implementation cannot detect loss of
frame alignment in case of loss of incoming signal.
- Alarm Indication Signal (AIS): this is detected when both of the two following conditions occur:
- loss of frame alignment;
- reception of 512 bit periods containing less than 3 ZEROs (reference is made to CCITT
Recommendation O.162 [7], paragraph 3.3.2).
- CRC error information: reception of one E bit set to ZERO according to table 5;

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