SIST ETS 300 686 E1:2005

• Abstract:

  Specification of the public network interface and test methods for compliance.

• Status: Published
• Publication Date: 31-Jan-2005
• ICS: 33.040.50 - Lines, connections and circuits
• Technical Committee: RES - Radio equipment and systems
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Feb-2005
• Due Date: 01-Feb-2005
• Completion Date: 01-Feb-2005
• Mandate: T-297
• Ref Project: ETSI ETS 300 686 ed.1 (1996-04) - Business TeleCommunications (BTC); 34 Mbit/s and 140 Mbit/s digital leased lines (D34U, D34S, D140U, D140S); Network interface presentation

SIST ETS 300 686 E1:2005 specifies the public network interface presentation for 34 Mbit/s and 140 Mbit/s Business TeleCommunications (BTC) digital leased lines, together with the conformance tests for that interface. It is the Slovenian standard identical to ETS 300 686 Edition 1, published by SIST. In practice, it tells network providers and equipment designers what the interface must look like at the Network Termination Point (NTP) and how compliance is checked.

What does SIST ETS 300 686 E1:2005 specify?

SIST ETS 300 686 E1:2005 defines the technical requirements for the leased line interface as presented by the provider at the NTP. It covers both unstructured and structured services for D34U, D34S, D140U and D140S, and it applies to leased lines whose establishment or release does not require protocol exchange or other intervention at the NTP.

The document is organized into four main clauses and four annexes. The main clauses cover the scope, references, definitions, and the interface requirements. The annexes provide the test methods, code definitions, and bibliography.

Annex	What it covers
Annex A	Normative test methods for compliance checking
Annex B	Normative definition of HDB3 code
Annex C	Normative definition of CMI code
Annex D	Informative bibliography

For structured services, the frame structure is defined in ETS 300 687 for 34 Mbit/s and ETS 300 688 for 140 Mbit/s. That matters because this standard defines the network interface presentation, while the companion standard defines the connection characteristics between NTPs.

What are the key requirements of SIST ETS 300 686 E1:2005?

SIST ETS 300 686 E1:2005 sets the physical interface, the line coding, the pulse shape, the impedance behavior, and the basic safety expectations for the network side of the connection. It also links each requirement to a named test method in Annex A, so the document is usable for design verification and compliance testing.

Interface presentation and connector arrangement

Clause 4.1 requires two coaxial 75 Ω sockets, one for transmit and one for receive. The sockets must be either 75 Ω Type 1,6/5,6 connectors or 75 Ω BNC sockets with the specified mating dimensions.

This matters because terminal equipment must match the physical connector type and impedance of the leased line interface. The outer conductor is connected to signal ground at both ports, so grounding and bonding need attention during installation.

34 Mbit/s electrical characteristics

Clause 4.2 defines the 34 Mbit/s interface for D34U and D34S. The output signal must use High Density Bipolar code 3 (HDB3), the pulse shape must fit the specified mask, and the output timing under network failure conditions must remain within the stated bit-rate tolerance.

In practice, this means the transmitter has to produce a line signal that is compatible with the line code and the pulse shape expected by the network. The input side must decode HDB3 without errors and tolerate cable loss and reflections within the specified limits.

140 Mbit/s electrical characteristics

Clause 4.3 defines the 140 Mbit/s interface for D140U and D140S. The output signal must use Coded Mark Inversion (CMI), the pulse shape must fit the two masks given for binary 0 and binary 1, and the output timing under failure conditions must stay within the stated tolerance.

For users, this means 140 Mbit/s equipment needs different coding and pulse behavior from the 34 Mbit/s case. The input side must decode CMI correctly and must remain error-free with the specified cable attenuation and impedance variation.

Return loss, loss tolerance, and reflections

For both speed classes, the standard sets minimum input and output return loss values, with different frequency ranges for 34 Mbit/s and 140 Mbit/s. Clause 4.2.2.3 and 4.3.2.3 also require the input port to decode correctly through a cable or artificial cable with a √f attenuation law and up to 12 dB attenuation at the stated reference frequency.

Clause 4.2.2.4 adds immunity against reflections for the 34 Mbit/s interface. That matters in practice because real cabling and connectors create mismatches, and the interface still has to work without bit errors.

Safety, overvoltage protection, and EMC

Clause 4.4 requires the leased line interface to comply with the requirements for accessible parts of a Safety Extra-Low Voltage (SELV) circuit. The tests associated with this clause are intended for equipment of the kind used to provide the interface, not for installed leased lines.

Clauses 4.5 and 4.6 state that there are no overvoltage protection requirements and no EMC requirements in this ETS. For a buyer or installer, that means those topics may still be governed by other obligations, but they are not specified here.

Test framework

Annex A explains how compliance tests are performed, including loopback support, pattern generation, cable simulators, and return-loss bridge measurements. Some tests are not meant for installed leased lines, which is important when deciding whether to test the live circuit or only the interface equipment.

What terms does SIST ETS 300 686 E1:2005 define?

• leased lines - Telecommunications facilities provided by a public network with defined transmission characteristics between NTPs and no user-controlled switching.
• Network Termination Point (NTP) - The physical network boundary and its access specifications where the leased line is presented.
• HDB3 - A modified Alternate Mark Inversion code used for the 34 Mbit/s interface, defined in Annex B.
• CMI - A two-level non-return-to-zero code used for the 140 Mbit/s interface, defined in Annex C.
• PRBS(2 -1) - A pseudo random bit sequence used as a test pattern in several conformance methods.
• SELV circuit - A secondary circuit designed so accessible parts remain at a safe voltage under normal and single fault conditions.
• D34U / D34S / D140U / D140S - The four leased line types covered by the standard, split into unstructured and structured variants at 34 Mbit/s and 140 Mbit/s.

Who uses SIST ETS 300 686 E1:2005?

SIST ETS 300 686 E1:2005 is used by leased line providers, terminal equipment manufacturers, test laboratories, and compliance teams. Network engineers use it to define the public-side interface at the NTP, while equipment designers use it to match connectors, coding, impedance, timing, and pulse shape.

Quality managers and buyers use it when checking whether equipment or a service presentation is suitable for D34U, D34S, D140U or D140S. It is also relevant to installation and acceptance testing, especially where interface conformance or line compatibility has to be documented.

Which standards are used with SIST ETS 300 686 E1:2005?

Standard	What it contributes
EN 60950	Safety requirements for information technology equipment, used for the SELV-related safety test
IEC 169-8	Requirements for 75 Ω BNC connectors
IEC 169-13	Requirements for 75 Ω coaxial connectors type 1,6/5,6
ISO/IEC 10173	Mating dimensions for the BNC option referenced by the connector requirement
ITU-T Recommendation G.703	Basis for the physical and electrical interface characteristics, pulse shapes and return loss limits
ITU-T Recommendation O.151	Definition source for PRBS(2 -1)

The foreword also names ETS 300 687, ETS 300 688, ETS 300 689 and ETS 300 690 as related BTC standards. ETS 300 687 and ETS 300 688 are the companion connection-characteristics standards for the 34 Mbit/s and 140 Mbit/s services.

What does the SIST ETS 300 686 E1:2005 document contain?

SIST ETS 300 686 E1:2005 contains the interface requirements for mechanical construction, line coding, waveform shape, timing under failure conditions, return loss, loss tolerance, and safety-related treatment of the interface. It also includes the test methods needed to verify those requirements at the NTP.

The document uses tables and figures to specify the pulse masks, voltage and frequency limits, and the test set-ups for coding, waveform, timing, loss, and return-loss measurements. Annex A gives the practical measurement arrangements, including loopback, cable simulators, combining networks, and bridge-based return-loss measurements.

Annex B and Annex C provide the code definitions needed to interpret the 34 Mbit/s and 140 Mbit/s signal rules. That makes the standard useful not only for compliance checking, but also for design review, laboratory testing, and interface matching during acceptance.

SLOVENSKI STANDARD
01-februar-2005
Poslovne telekomunikacije (BTC) - Digitalni zakupljeni vodi za prenosni hitrosti 34
Mbit/s in 140 Mbit/s (D34U, D34S, D140U, D140S) - Omrežni vmesnik
Business TeleCommunications (BTC); 34 Mbit/s and 140 Mbit/s digital leased lines
(D34U, D34S, D140U, D140S); Network interface presentation
Ta slovenski standard je istoveten z: ETS 300 686 Edition 1
ICS:
33.040.50 Vodi, zveze in tokokrogi Lines, connections and
circuits
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 686
TELECOMMUNICATION March 1996
STANDARD
Source: ETSI TC-BTC Reference: DE/BTC-02053
ICS: 33.020
Key words: leased line, network, interface, D34U, D34S, D140U, D140S
Business TeleCommunications (BTC);
34 Mbit/s and 140 Mbit/s digital leased lines
(D34U, D34S, D140U and D140S);
Network interface presentation
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
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail]
Tel.: [phone] - Fax: [phone]
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 1996. All rights reserved.

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ETS 300 686: March 1996
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 300 686: March 1996
Contents
Foreword .5
Introduction.5
1 Scope .7
2 Normative references.7
3 Definitions and abbreviations .8
3.1 Definitions .8
3.2 Abbreviations .8
4 Requirements.9
4.1 Mechanical characteristics.9
4.2 Electrical characteristics - 34 Mbit/s .10
4.2.1 Output port .10
4.2.1.1 Signal coding at the output port.10
4.2.1.2 Waveform shape .10
4.2.1.3 Output timing under failure conditions .11
4.2.1.4 Output return loss .11
4.2.1.5 Output timing and jitter .11
4.2.2 Input port .12
4.2.2.1 Signal coding at the input port .12
4.2.2.2 Input return loss.12
4.2.2.3 Input loss tolerance.12
4.2.2.4 Immunity against reflections .12
4.2.2.5 Input timing and jitter tolerance .12
4.3 Electrical characteristics - 140 Mbit/s .13
4.3.1 Output port .13
4.3.1.1 Signal coding at the output port.13
4.3.1.2 Waveform shape .13
4.3.1.3 Output timing under failure conditions .15
4.3.1.4 Output return loss .15
4.3.1.5 Output timing and jitter .16
4.3.2 Input port .16
4.3.2.1 Signal coding at the input port .16
4.3.2.2 Input return loss.16
4.3.2.3 Input loss tolerance.16
4.3.2.4 Input timing and jitter tolerance .16
4.4 Safety.16
4.5 Overvoltage protection.17
4.6 ElectroMagnetic Compatibility (EMC) .17
Annex A (normative): Test methods.18
A.1 General.18
A.1.1 Additional information to support the test .18
A.1.2 Equipment connection .18
A.2 Test methods .18
A.2.1 Signal coding at the output port .18
A.2.1.1 Signal coding at the output port - 34 Mbit/s.18
A.2.1.2 Signal coding at the output port - 140 Mbit/s.19
A.2.2 Waveform shape at the output port .20
A.2.2.1 Waveform shape at the output port - 34 Mbit/s.20
A.2.2.2 Waveform shape at the output port - 140 Mbit/s.20

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ETS 300 686: March 1996
A.2.3 Output timing under failure conditions. 21
A.2.4 Input signal coding, loss tolerance and immunity against reflections. 22
A.2.4.1 Input signal coding, loss tolerance and immunity against reflections -
34 Mbit/s . 22
A.2.4.2 Input signal coding and loss tolerance - 140 Mbit/s. 23
A.2.5 Input return loss. 24
A.2.6 Output return loss. 25
Annex B (normative): Definition of HDB3 code. 27
B.1 General. 27
B.2 Definition. 27
Annex C (normative): Definition of CMI code. 28
C.1 General. 28
C.2 Definition. 28
Annex D (informative): Bibliography . 29
History. 30

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ETS 300 686: March 1996
Foreword
This European Telecommunication Standard (ETS) has been produced by the Business
TeleCommunications (BTC) Technical Committee of the European Telecommunications Standards
Institute (ETSI).
This ETS resulted from a mandate from the Commission of the European Community (CEC) to provide
harmonised standards for the support of the Directive on Open Network Provision (ONP) of leased lines
(92/44/EEC).
There are four other standards directly related to this ETS:
- ETS 300 687: "Business TeleCommunications (BTC); 34 Mbit/s digital leased lines (D34U and
D34S); Connection characteristics";
- ETS 300 688: "Business TeleCommunications (BTC); 140 Mbit/s digital leased lines (D140U and
D140S); Connection characteristics";
- ETS 300 689: "Business TeleCommunications (BTC); 34 Mbit/s digital leased lines (D34U and
D34S); Terminal equipment interface";
- ETS 300 690: "Business TeleCommunications (BTC); 140 Mbit/s digital leased lines (D140U and
D140S); Terminal equipment interface".
Transposition dates
Date of adoption of this ETS: 15 March 1996
Date of latest announcement of this ETS (doa): 30 June 1996
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 December 1996
Date of withdrawal of any conflicting National Standard (dow): 31 December 1996
This ETS is based on information from ITU-T Recommendations and ETSI publications and the relevant
documents are quoted where appropriate.
Introduction
The Council Directive on the application of Open Network Provision (ONP) to leased lines (92/44/EEC)
concerns the harmonisation of conditions for open and efficient access to, and use of, the leased lines
provided over public telecommunications networks, and the availability throughout the European Union of
a minimum set of leased lines with harmonised technical characteristics.
The 34 Mbit/s and 140 Mbit/s unstructured and structured leased lines are not part of the minimum set of
leased lines under the leased line Directive, however these standards are being written with the intention
that where 34 Mbit/s or 140 Mbit/s leased lines are offered, they will be in accordance with these
harmonised standards.
Under the Second Phase Directive (91/263/EEC), terminal equipment for connection to these leased lines
will be required to fulfil certain essential requirements.
ETS 300 166 and ITU-T Recommendation G.703 are used as the basis for the interface presentation
requirements.
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ETS 300 686: March 1996
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ETS 300 686: March 1996
1 Scope
This ETS specifies the technical requirements and conformance tests for the network interface
presentations of 34 Mbit/s and 140 Mbit/s digital leased lines. This includes:
- the 34 Mbit/s Digital Unstructured leased line operating at 34 368 kbit/s;
- the 140 Mbit/s Digital Unstructured leased line operating at 139 264 kbit/s;
- the 34 Mbit/s digital structured leased line operating at 34 368 kbit/s for the support of an
unstructured 33 920 kbit/s information transfer rate;
- the 140 Mbit/s digital structured leased line operating at 139 264 kbit/s for the support of an
unstructured 138 240 kbit/s information transfer rate.
A connection is presented via interfaces at Network Termination Points (NTPs). This ETS defines the
network interface as presented by the leased line provider and should be used in conjunction with the
appropriate companion standard, ETS 300 687 (34 Mbit/s) or ETS 300 688 (140 Mbit/s), which specifies
the connection characteristics between NTPs of the leased line. This ETS and the appropriate connection
characteristics standard together describe the technical characteristics of the relevant leased line.
This ETS is applicable to leased lines, including part time leased lines, whose establishment or release
does not require any protocol exchange or other intervention at the NTP.
This ETS covers the mechanical and electrical characteristics of the network interface and specifies the
conformance tests for equipment of the kind that provides the interface presentation. Some of the tests
described in this ETS are not designed to be applied to the interface of an installed leased line; such tests
may be applied to equipment of the kind used to provide the interface. This ETS does not include details
concerning the implementation of the tests nor does it include information on any regulations concerning
testing. There is no requirement for each leased line to be tested in accordance with this ETS before it is
brought into service or returned into service following repair.
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 into it by amendment or revision. For undated references the
latest edition of the publication referred to applies.
[1] EN 60950 (1992): "Safety of information technology equipment including
electrical business equipment".
[2] IEC 169-8:1978: "Radio frequency connectors - Part 8: R.F coaxial connectors
with inner diameters of outer conductor 6,5 mm (0,256 in) with bayonet lock -
Characteristic impedance 50 ohms (Type BNC)".
[3] IEC 169-13 (1976): Part 13: "R.F. coaxial connectors with inner diameter of
outer conductor 5,6 mm (0,22 in) - Characteristic impedance 75 ohms
(Type 1,6/5,6) - Characteristic impedance 50 ohms (Type 1,8/5,6) with similar
mating dimensions".
[4] ISO/IEC 10173 (1991): "Information technology - Integrated Services Digital
Network (ISDN) primary access connector at reference points S and T".
[5] ITU-T Recommendation G.703 (1991): "Physical/electrical characteristics of
hierarchical digital interfaces".
[6] ITU-T Recommendation O.151 (1992): "Error performance measuring
equipment for digital systems at the primary rate and above".

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ETS 300 686: March 1996
NOTE: This ETS also contains a number of informative references which have been included
to indicate the sources from which various material has been derived, hence they do
not have an associated normative reference number. Details of these publications are
given in annex D. In some cases the same publication may have been referenced in
both a normative and an informative manner.
3 Definitions and abbreviations
For the purposes of this ETS, the following definitions apply:
3.1 Definitions
leased lines: The telecommunications facilities provided by a public telecommunications network that
provide defined transmission characteristics between network termination points and that do not include
switching functions that the user can control, (e.g. on-demand switching).
Network Termination Point (NTP): All physical connections and their technical access specifications
which form part of the public telecommunications network and are necessary for access to and efficient
communication through that public network.
PRBS(2 -1): A Pseudo Random Bit Sequence (PRBS) (as defined in subclause 2.2 of
ITU-T Recommendation O.151 [6]).
Safety Extra-Low Voltage (SELV) circuit: A secondary circuit which is so designed and protected that
under normal and single fault conditions, the voltage between any two accessible parts and, for class 1
equipment, between any accessible part and the equipment protective earthing terminal does not exceed
a safe value (subclause 1.2.8.5 of EN 60950 [1]).
3.2 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
ac alternating current
AMI Alternate Mark Inversion
BNC Bayonet Nut Connector
CMI Coded Mark Inversion
D140S 140 Mbit/s Digital Structured leased line
D140U 140 Mbit/s Digital Unstructured leased line
D34S 34 Mbit/s Digital Structured leased line
D34U 34 Mbit/s Digital Unstructured leased line
dc direct current
EMC ElectroMagnetic Compatibility
HDB3 High Density Bipolar code 3
NTP Network Termination Point
ONP Open Network Provision
ppm parts per million
PRBS Pseudo Random Bit Sequence
RX RX is a signal input (at either the leased line interface or the test equipment, see
figure 1)
SELV Safety Extra-Low Voltage
TX TX is a signal output (at either the leased line interface or the test equipment,
see figure 1)
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ETS 300 686: March 1996
4 Requirements
These requirements define the network interface presentation for:
- the 34 Mbit/s Digital Unstructured leased line (D34U) which provides a bi-directional point-to-point
digital transmission capability with a usable bit rate of 34 368 kbit/s - no structuring of the data is
provided, or shall be required, by the network and any structuring is the responsibility of the user;
- the 140 Mbit/s Digital Unstructured leased line (D140U) which provides a bi-directional
point-to-point digital transmission capability with a usable bit rate of 139 264 kbit/s - no structuring of
the data is provided, or shall be required, by the network and any structuring is the responsibility of
the user;
- the 34 Mbit/s Digital Structured leased line (D34S) which provides a bi-directional point-to-point
digital transmission capability for the support of an unstructured 33 920 kbit/s information transfer
rate; the frame structure in the 34 368 kbit/s bit stream is defined in ETS 300 687 - any structuring
of the data within the transparent 33 920 kbit/s part of the frame is the responsibility of the user;
- the 140 Mbit/s Digital Structured leased line (D140S) which provides a bi-directional point-to-point
digital transmission capability for the support of an unstructured 138 240 kbit/s information transfer
rate; the frame structure in the 139 264 kbit/s bit stream is defined in ETS 300 688 - any structuring
of the data within the transparent 138 240 kbit/s part of the frame is the responsibility of the user.
The provision of timing is the responsibility of the user, however in certain installations, the leased line
provider may be able to offer a service which is synchronised to the network.
NOTE 1: The network interface is not designed for power feeding capabilities.
NOTE 2: If equipment providing the interface requires a mains supply, the leased line provider
should bring this to the attention of the user so that the user can provide mains supply
back-up facilities, if required.
The mechanical characteristics, safety, overvoltage protection requirements and ElectroMagnetic
Compatibility (EMC) requirements are common for the 34 Mbit/s and 140 Mbit/s leased lines. The
electrical characteristics are different and are defined in separate subclauses.
4.1 Mechanical characteristics
Requirement: The network interface shall provide two coaxial 75 Ω sockets, one each for transmit and
receive, these sockets being either:
a) 75 Ω sockets (type 1,6/5,6) complying with IEC 169-13 [3]; or
b) 75 Ω BNC sockets complying with the general requirements of IEC 169-8 [2] with the mating
dimensions specified in annex B of ISO/IEC 10173 [4].
The outer conductor of the coaxial pair shall be connected to signal ground both at the input port and at
the output port.
NOTE 1: When connecting the terminal equipment to the Network Termination Point (NTP), any
difference in ground potential between the two equipments may produce a voltage
across the signal ground connection and may cause damage. See DEN/EE-02004 for
details of earthing requirements within the customer's premises.
NOTE 2: The transmit pair is the output from the network interface. The receive pair is the input
to the network interface, as shown in figure 1. Where the terms "output" and "input" are
used without qualification in this ETS, they refer to the network interface.

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ETS 300 686: March 1996
OUTPUT INPUT
TX RX
TERMINAL
NETWORK
EQUIPMENT
INTERFACE
INTERFACE
RX TX
INPUT OUTPUT
Figure 1
Test: There shall be a visual inspection that the sockets are of the correct type.
4.2 Electrical characteristics - 34 Mbit/s
4.2.1 Output port
4.2.1.1 Signal coding at the output port
Requirement: The signal transmitted at the output port shall comply with the High Density Bipolar code 3
(HDB3) encoding rules (see annex B).
Test: The test shall be conducted according to subclause A.2.1.1.
4.2.1.2 Waveform shape
Requirement: The pulse at the output port shall comply with the requirements given in figure 2 and
table 1, based on ITU-T Recommendation G.703.
Test: The test shall be conducted according to subclause A.2.2.1.
Table 1: Waveform shape at output port
Pulse shape (nominally rectangular) All marks of a valid signal shall conform with the
mask (see figure 2). The value V corresponds to
the nominal peak voltage of a mark.
Test load impedance
75 Ω non-reactive
Nominal peak voltage V of a mark 1,0 V
Peak voltage of a space 0 ± 0,1 V
Nominal pulse width 14,55 ns
Ratio of the amplitudes of positive and negative 0,95 to 1,05
pulses at the centre of the pulse interval
Ratio of the widths of positive and negative pulses 0,95 to 1,05
at the nominal half amplitude
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ETS 300 686: March 1996
17 ns
(14,55 + 2,45)
V
0,2
0,1
1,0
8,65 ns
0,1
(14,55 - 5,90)
0,2
Nominal
pulse
14,55 ns
0,5
12,1 ns
(14,55 - 2,45)
24,5
0,1 (14,55 + 9,95) 0,1
0,1
0,1
0,2
29,1 ns
(14,55 + 14,55)
Figure 2: Pulse mask for 34 Mbit/s pulse
4.2.1.3 Output timing under failure conditions
Requirement: When there is a failure within the network and if a signal is presented at the network
interface output, the output timing shall be 34 368 kbit/s ± 20 ppm.
Test: The test shall be conducted according to subclause A.2.3.
4.2.1.4 Output return loss
Requirement: The output return loss at the network interface, with respect to 75 Ω, shall be greater than
or equal to the values given in table 2, which is based on annex 3 of ETS 300 166.
Table 2: Output port minimum return loss
Frequency range Return loss
860 kHz to 1 720 kHz 6 dB
1 720 kHz to 51 550 kHz 8 dB
Test: The test shall be conducted according to subclause A.2.6.
4.2.1.5 Output timing and jitter
NOTE: Output timing requirements and jitter limits for the D34U and D34S leased lines are
specified in the connection standard ETS 300 687.

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ETS 300 686: March 1996
4.2.2 Input port
4.2.2.1 Signal coding at the input port
Requirement: The input port shall decode High Density Bipolar code 3 (HDB3) encoded signals without
error in accordance with HDB3 encoding rules (see annex B).
Test: The test shall be conducted according to subclause A.2.4.1.
4.2.2.2 Input return loss
Requirement: The input return loss at the network interface, with respect to 75 Ω, shall be greater than or
equal to the values given in table 3, which is taken from subclause 8.3.3 of
ITU-T Recommendation G.703.
Table 3: Input port minimum return loss
Frequency range Return loss
860 kHz to 1 720 kHz 12 dB
1 720 kHz to 34 368 kHz 18 dB
34 368 kHz to 51 550 kHz 14 dB
Test: The test shall be conducted according to subclause A.2.5.
4.2.2.3 Input loss tolerance
Requirement: The input port shall correctly decode without errors a 34 368 kbit/s signal as defined in
4.2.1.1 and 4.2.1.2 above but modified by a cable or artificial cable with the following characteristics:
a) attenuation that follows a √f law with values throughout the range 0 dB to 12 dB at 17 184 kHz; and
b) characteristic impedance of 75 Ω with a tolerance of ± 20 % over the frequency range 860 kHz to
51 550 kHz.
Test: The test shall be conducted according to subclause A.2.4.1.
4.2.2.4 Immunity against reflections
Requirement: When a signal comprising a combination of a normal signal and an interfering signal is
applied to the input port, via an artificial cable with a loss in the range 0 dB to 12 dB at 17 184 kHz, no
errors shall result due to the interfering signal. The normal signal shall be a signal encoded according to
HDB3, shaped according to the mask of figure 2, with a binary content in accordance with a PRBS(2 -1).
The interfering signal shall be the same as the normal signal except that the level shall be attenuated by
20 dB, the bit rate shall be within 34 368 kbit/s ± 20 ppm and the timing shall not be synchronised to the
normal signal.
Test: The test shall be conducted according to subclause A.2.4.1.
4.2.2.5 Input timing and jitter tolerance
NOTE: Input timing requirements and jitter tolerance for the D34U and D34S leased lines are
specified in the connection standard ETS 300 687.

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ETS 300 686: March 1996
4.3 Electrical characteristics - 140 Mbit/s
4.3.1 Output port
4.3.1.1 Signal coding at the output port
Requirement: The signal transmitted at the output port shall comply with the Coded Mark Inversion (CMI)
encoding rules (see annex C).
Test: The test shall be conducted according to subclause A.2.1.2.
4.3.1.2 Waveform shape
Requirement: The pulse at the output port shall comply with the requirements given in figures 3 and 4
and table 4, based on ITU-T Recommendation G.703.
Table 4: Waveform shape at output port
Pulse shape Nominally rectangular and c
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