EN 61935-1:2005

SLOVENSKI SIST EN 61935-1:2006

STANDARD
marec 2006
Preskušanje urejenega kabliranja za komunikacije v skladu s standardom EN
50173 – 1. del: Kabelska inštalacija (IEC 61935-1:2005, spremenjen)
Testing of balanced communication cabling in accordance with standards series
EN 50173 - Part 1: Installed cabling (IEC 61935-1:2005, modified)
ICS 33.120.10 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD EN 61935-1
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2005

ICS 33.120.10 Supersedes EN 61935-1:2000 + A1:2002

English version
Testing of balanced communication cabling
in accordance with standards series EN 50173
Part 1: Installed cabling
(IEC 61935-1:2005, modified)
Essais de câblages de Prüfung der symmetrischen
télécommunications symétriques Kommunikationsverkabelung
selon la série de normes EN 50173 nach der Normenreihe EN 50173
Partie 1: Câblages installés Teil 1: Installierte Verkabelung
(CEI 61935-1:2005, modifiée) (IEC 61935-1:2005, modifiziert)

This European Standard was approved by CENELEC on 2005-10-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61935-1:2005 E
Foreword
The text of document 46A/717/FDIS, future edition 2 of IEC 61935-1, prepared by SC 46A, Coaxial
cables, of IEC TC 46, Cables, wires, waveguides, R.F. connectors, R.F. and microwave passive
components and accessories, was submitted to the IEC-CENELEC parallel vote and was approved by
CENELEC as EN 61935-1 on 2005-10-01.
This European Standard supersedes EN 61935-1:2000 + corrigendum February 2001 + A1:2002.
This new edition was written to describe Level IV testers in support of ISO/IEC 11801:2002 and the series
EN 50173.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-07-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-10-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61935-1:2005 was approved by CENELEC as a European
Standard with agreed common modifications as given below.
COMMON MODIFICATIONS
Title page
Replace "ISO/IEC 11801" by "standards series EN 50173".
General
Replace all other occurrences of "ISO/IEC 11801" and "ISO/IEC 11801 (or equivalent)" by "EN 50173".
This replacement is to be made in the introduction and in (Sub)Clauses 3, 3.1, 4.2.4 (twice), 5.1 (four
times), 5.3.1, 5.3.2.2, 5.3.3, 5.3.4 (twice), 5.3.5, 5.3.6, 5.3.8, 5.3.9, 5.3.10, 5.5.1, 6.2 and 6.8.1.
Clause 1, Scope
Replace the first paragraph by:
This part of EN 61935 specifies reference measurement procedures for cabling parameters and the
requirements for field tester accuracy to measure cabling parameters identified in EN 50173.
Clause 2, Normative references
Add:
EN 50173, series, Information technology - Generic cabling systems

- 3 - EN 61935-1:2005
Clause 3, Terms and definitions
Replace definitions 3.2 and 3.3 by:
3.2
reflection coefficient
ratio of the voltage of the reflected wave to the voltage of the incident wave at the port or transverse
cross-section to a cable assembly when the cable assembly is terminated with its application or nominal
impedances, Z .
cnom
ZZ−
cnom in
C = (1)
r
ZZ+
cnom in
3.3
return loss
ratio in decibels of the voltage delivered to a cable assembly terminated at the far end with its nominal
characteristic impedance, to the reflected voltage at the input port of the cable assembly.
u
i
R = 20log
l
u
r
or
ZZ+
cnom in
R = 20log (2)
l
ZZ−
cnom in
where
u is the incident voltage;
i
u is the reflected voltage.
r
___________
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year
– Information technology - Generic cabling systems EN 50173 Series

1)
IEC 60169-16 – Radio-frequency connectors – –
Part 16: R.F. coaxial connectors with inner
diameter of outer conductor 7 mm (0,276 in)
with screw coupling - Characteristic impedance
50 ohms (75 ohms) (Type N)
1)
IEC 60169-22 – Part 22: R.F. two-pole bayonet coupled – -
connectors for use with shielded balanced cables
having twin inner conductors (Type BNO)

IEC 60603-7 1996 Connectors for frequencies below 3 MHz for use EN 60603-7 1997
with printed boards
Part 7: Detail specification for connectors, 8-way,
including fixed and free connectors with common
mating features, with assessed quality

1) 2)
IEC 61076-3-104 – Connectors for electronic equipment EN 61076-3-104 2003
Part 3-104: Rectangular connectors - Detail
specification for 8-way, shielded free and fixed
connectors for data transmissions with
frequencies up to 600 MHz minimum

3) 1)
ISO/IEC 14763-1 – Information technology – Implementation and – –
operation of customer premises cabling
Part 1: Administration
ITU-T Rec. G.117 1996 Transmission aspects of unbalance about earth – –

ITU-T Rec. O.9 1988 Measuring arrangements to assess the degree of – –
unbalance about earth
1)
Undated reference.
2)
Valid edition at date of issue.
3)
EN 50174-1, Information technology - Cabling installation -- Part 1: Specification and quality assurance, which is related to, but
not directly equivalent with ISO/IEC 14763-1, applies instead.

NORME CEI
INTERNATIONALE
IEC
61935-1
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2005-08
Essais de câblages de télécommunications
symétriques selon l'ISO/IEC 11801 –
Partie 1:
Câblages installés
Testing of balanced communication
cabling in accordance with ISO/IEC 11801 –
Part 1:
Installed cabling
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61935-1  IEC:2005 – 3 –
CONTENTS
FOREWORD.7
INTRODUCTION.11

1 Scope.13
2 Normative references .13
3 Terms and definitions .15
4 Reference measurement procedures for electrical properties .21
4.1 General .21
4.2 Test equipment considerations .21
4.3 DC loop resistance .33
4.4 Direct current (d.c.) resistance unbalance .35
4.5 Insertion loss.39
4.6 Propagation delay and delay skew .41
4.7 Near-end crosstalk (NEXT), pair to pair and power sum .45
4.8 Attenuation to crosstalk ratio (ACR), pair to pair and power sum .49
4.9 Far-end crosstalk (FEXT), pair to pair and power sum .51
4.10 Equal level far-end crosstalk (ELFEXT) .57
4.11 Return loss.57
4.12 Unbalance attenuation.61
4.13 Coupling attenuation .61
5 Field test measurement requirements for electrical properties .61
5.1 General .61
5.2 Cabling configurations tested .63
5.3 Field test parameters.63
5.4 Data reporting and accuracy.75
5.5 Field measurement procedures .87
6 Field tester measurement accuracy requirements .89
6.1 General .89
6.2 Measurement accuracy specifications common to level IIE, level III and
level IV field testers.93
6.3 Accuracy performance requirements for level IIE field testers.93
6.4 Accuracy performance requirements for level III field testers .97
6.5 Accuracy performance requirements for level IV field testers.101
6.6 Procedures for determining field tester parameters .105
6.7 Measurement error models.121
6.8 Network analyser measurement comparisons .133

Bibliography.147

61935-1  IEC:2005 – 5 –
Figure 1 – Resistor load.23
Figure 2 – Reference planes for permanent link and channel .25
Figure 3 – 180° hybrid used as a balun.27
Figure 4 – Loop resistance measurement .35
Figure 5 – DC resistance unbalance measurement (test configuration for one wire).37
Figure 6 – Insertion loss test configuration.39
Figure 7 – NEXT test configuration .47
Figure 8 – FEXT test configuration.53
Figure 9 – Return loss test configuration.59
Figure 10 – Correct pairing .65
Figure 11 – Incorrect pairing .65
Figure 12 – Example of equipment tolerance region (NEXT) .75
Figure 13 – Block diagram for measuring output signal balance .107
Figure 14 – Block diagram to measure common mode rejection .109
Figure 15 – Block diagram for measuring residual NEXT.111
Figure 16 – Block diagram for measuring dynamic accuracy .111
Figure 17 – Principle of measurement of residual NEXT .115
Figure 18 – Principle of alternate measurement of residual FEXT .115
Figure 19 – Construction details of special patch cord adapter.135
Figure 20 – Interfaces to channel by field test and laboratory equipment to compare
test results.137
Figure 21 – Interfaces to link test configuration by field test and laboratory equipment
to compare test results .139
Figure 22 – Sample scatter plot .143

Table 1 – Test balun performance characteristics .29
Table 2 – Summary of reporting requirements for field test equipment .79
Table 3 – Worst case propagation delay, delay skew, d.c. resistance and length
measurement accuracy for level IIE, level III and level IV test instruments.91
Table 4 – Worst case insertion loss, NEXT, ACR, ELFEXT and return loss
measurement accuracy for level IIE field test instruments .91
Table 5 – Worst case measurement insertion loss, NEXT, ACR, ELFEXT and return
loss for level III test instruments .91
Table 6 – Worst case insertion loss, NEXT, ACR, ELFEXT and return loss
measurement for level IV test instruments .93
Table 7 – Propagation delay, delay skew, DC resistance and length accuracy
performance specifications .93
Table 8 – Level IIE field tester accuracy performance parameters per IEC guidelines .95
Table 9 – Level III field tester accuracy performance parameters per IEC guidelines .99
Table 10 – Level IV field tester accuracy performance parameters per IEC guidelines .103

61935-1  IEC:2005 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
TESTING OF BALANCED COMMUNICATION
CABLING IN ACCORDANCE WITH ISO/IEC 11801 –

Part 1: Installed cabling
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61935-1 has been prepared by subcommittee 46A: Coaxial cables,
of IEC technical committee 46: Cables, wires, waveguides, r.f. connectors, r.f. and microwave
passive components and accessories.
This second edition cancels and replaces the first edition published in 2000 and amendment 1
(2002). It constitutes a technical revision.
This second edition was written to describe Level IV testers in support of the second edition
of ISO/IEC 11801.
61935-1  IEC:2005 – 9 –
The text of this standard is based on the following documents:
FDIS Report on voting
46A/717/FDIS 46A/734/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 61935 consists of the following parts, under the general title Testing of balanced
communication cabling in accordance with ISO/IEC 11801:
Part 1: Installed cabling
Part 2: Patch cords and work area cords
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
61935-1  IEC:2005 – 11 –
INTRODUCTION
Telecommunication cabling, once specified uniquely by each telecommunications application,
has evolved into a generic cabling system. Telecommunications applications now use the
ISO/IEC 11801 cabling standard to meet their cabling requirements. Formerly, connectivity
tests and visual inspection were deemed sufficient to verify a cabling installation. Now users
need more comprehensive testing in order to ensure that the link will support
telecommunications applications that are designed to operate on the generic cabling system.
This part of IEC 61935 addresses reference laboratory and field test methods and provides a
comparison of these methods.
Transmission performance depends on cable characteristics, connecting hardware, patch
cords and cross-connect cabling, the total number of connections, and the care with which
they are installed and maintained. This standard provides test methods for installed cabling
and pre-fabricated cable assemblies. These test methods, where appropriate, are based on
those used for components of the cable assembly.
This part 1 contains the test methods required for installed cabling. Part 2 contains the test
methods required for patch cords and work area cords.

61935-1  IEC:2005 – 13 –
TESTING OF BALANCED COMMUNICATION
CABLING IN ACCORDANCE WITH ISO/IEC 11801 –

Part 1: Installed cabling
1 Scope
This part of IEC 61935 specifies reference measurement procedures for cabling parameters
and the requirements for field tester accuracy to measure cabling parameters identified in
ISO/IEC 11801. References in this standard to ISO/IEC 11801 mean ISO/IEC 11801 or
equivalent cabling standards.
This standard applies when the cable assemblies are constructed of cables complying with
IEC 61156 -1, IEC 61156-2, IEC 61156-3 IEC 61156-4, IEC 61156-5 or IEC 61156-6, and
connecting hardware as specified in IEC 60603-7 or IEC 61076-3-104. In the case where
cables and/or connectors do not comply with these standards then additional tests may be
required.
This standard is organized as follows:
• reference laboratory measurement procedures are specified in Clause 4. In some cases,
these procedures may be used in the field;
• descriptions and requirements for measurements in the field are specified in Clause 5;
• performance requirements for field testers and procedures to verify performance are
specified in Clause 6.
NOTE 1 This standard does not include tests that are normally performed on the cables and connectors
separately. These tests are described in IEC 61156-1 and IEC 60603-7 or IEC 61076-3-104 respectively.
NOTE 2 Wherever possible, cables and connectors used in cable assemblies, even if they are not described in
IEC 61156 or IEC 60603-7/IEC 61076-3-104 shall be tested separately according to the tests given in the relevant
generic specification. In this case, most of the environmental and mechanical tests described in this standard may
be omitted.
NOTE 3 Users of this standard are advised to consult with applications standards, equipment manufacturers and
system integrators to determine the suitability of these requirements for specific networking applications
This standard relates to performance with respect to 100 Ω cabling. For 120 Ω or 150 Ω
cabling, the same principles apply but the measurement system should correspond to the
nominal impedance level.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60169-16, Radio-frequency connectors – Part 16: R.F. coaxial connectors with inner
diameter of outer conductor 7 mm (0.276 in) with screw coupling – Characteristic impedance
50 ohms (75 ohms) (Type N)
61935-1  IEC:2005 – 15 –
IEC 60169-22, Radio-frequency connectors – Part 22: RF two-pole bayonet coupled
connectors for use with shielded balanced cables having twin inner conductors (Type BNO)
IEC 60603-7:1996 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, with assessed quality
IEC 61076-3-104, Connectors for electronic equipment – Part 3-104: Rectangular connectors
– Detail specification for 8-way, shielded free and fixed connectors for data transmissions with
frequencies up to 600 MHz minimum
ISO/IEC 11801, Information technology – Generic cabling for customer premises
ISO/IEC 14763-1, Information technology – Implementation and operation of customer
premises cabling – Part 1: Administration
ITU-T Recommendation G.117:1996, Transmission aspects of unbalance about earth
ITU-T Recommendation O.9:1999, Measuring arrangements to assess the degree of
unbalance about earth
3 Terms and definitions
For the purposes of this document, the terms and definitions in IS0/IEC 11801 and the
following apply.
3.1
cable assembly
combination of cable(s) and connector(s) with specified performance, used as a single unit
intended to be a part of a cabling link as defined in ISO/IEC 11801 (or equivalent).
Examples: patch cord, work area cord, link
3.2
reflection coefficient
ratio of the complex square root of wave amplitude of the reflected wave to the complex
square root of wave amplitude of the incident wave at a port or transverse cross-section of a
cable assembly when the cable assembly is terminated with its application or nominal
impedances, Z
nom
 | Z +Z |
in cnom
 
C = (1)
r
 
| Z −Z |
 in cnom 
3.3
return loss
ratio of the power delivered to a cable assembly terminated at the far end with its nominal
characteristic impedance, to the reflected power at the input port of the cable assembly

61935-1  IEC:2005 – 17 –
 
u
i
 
R =20 log
l
 
u
r
 
| Z −Z |
 
in cnom
 
or R =20 log (2)
l
 
| Z +Z |
in cnom
 
where
u is the incident voltage;
i
u is the reflection voltage.
r
3.4
electrical length
equivalent free-space length of the cable assembly
3.5
propagation delay
phase delay at each frequency in the frequency range of interest for the propagation of a
transverse electromagnetic mode (TEM) wave between the reference planes of the cable
assembly, expressed in nanoseconds per metre (ns/m)
3.6
minimum static bending radius
radius used in climatic tests which is the minimum permissible for fixed installations of the
cable
3.7
dynamic bending radius
bending radius used for the insertion loss stability, stability of electrical length and flexing
endurance tests. It is the minimum bending radius for applications where the cable assembly
is flexed. Larger bending radii will allow an increase in the maximum number of flexures
3.8
screening attenuation (of the cable assembly)
ratio of the common mode square root of power wave inside a screened cable assembly to the
total square root of power that radiates outside the cable assembly
3.9
unbalanced attenuation
ratio of the common mode square root of signal power to the differential mode square root of
signal power in a pair due to unbalanced properties of the given pair
3.10
near-end crosstalk
NEXT
near end measurement of the square root of signal power coupling from one circuit to another
within a cable assembly when a square root of signal power is fed and measured at the same
end. It is expressed in dB relative to the incident square root of signal power

61935-1  IEC:2005 – 19 –
3.11
far-end crosstalk
FEXT
measurement of square root of signal power coupling from the transmitting pair to a
neighbouring pair at the far end. It is expressed in dB relative to the incident signal level
3.12
equal level far-end crosstalk
ELFEXT
FEXT minus the insertion loss of the disturbed pair when both numbers are expressed in dB
3.13
comparative test
test that is performed to check the deviation between the results obtained with the reference
test method and those obtained with another test set-up (i.e. field test eguipment)
3.14
nominal impedance
impedance for which the system is designed. The nominal impedance is resistive
3.15
reference plane
reference position of the cabling element under test or necessary mating connector at which
the performance requirements are specified
3.16
power sum
NEXT and FEXT and ELFEXT
power sum crosstalk takes in the combined crosstalk on a receiving pair from all disturbers
operating simultaneously
3.17
delay skew
worst case value of the phase delay difference between any pair in the same cable assembly
3.18
output signal balance
OSB
ratio of the output common mode voltage to the output differential voltage generated by a
source port
3.19
d.c. resistance
d.c. loop resistance is a measure of the sum total of the d.c. resistance of the wires of a wire
pair
3.20
pair-to-pair ACR
difference between the pair-to-pair NEXT and the insertion loss (IL) of
the cabling in dB
3.21
power sum ACR
difference between the power sum NEXT and the insertion loss (IL) of
the cabling in dB
61935-1  IEC:2005 – 21 –
4 Reference measurement procedures for electrical properties
4.1 General
This Clause describes reference measurement procedures for electrical parameters. The
measurement procedures are intended to be used in a laboratory environment using
laboratory equipment. In some cases, a measurement procedure may also be applicable for
field testing. If this is the case, the procedure shall be specifically identified as being suitable
for field testing and appropriate precautions shall be described.
4.2 Test equipment considerations
The reference measurement procedures that are described in this standard require the use of
a network analyser, r.f. transformers (baluns), twisted pair (TP) test leads and impedance
matching terminations. Separate generator/receiver test instrumentation may also be used for
some of the measurements. Other measurement procedures, which can be shown to yield
equivalent results, may be used.
4.2.1 Network analyser test requirements
Usually the input and output terminals of a network analyser are unbalanced. R.F.
transformers with balanced outputs (baluns) are required with unbalanced signal connections
to the network analyser.
The test set-up shall be calibrated at the specified reference plane for the element under test
before testing. Full one-port calibrations shall be used when making one-port (e.g. return loss)
measurements. Full two-port calibration shall be used when making two-port measurements
(e.g. insertion loss) measurements.
4.2.2 Termination of conductor pairs
During measurement, all conductor pairs of the element under test shall be terminated at both
ends with impedance matching loads. For pairs under test, this is provided by the test
instrumentation at one or both ends. For pairs not under test or not connected to test
instrumentation, resistor loads or terminated baluns shall be applied.
Unless otherwise specified, the nominal differential mode impedance of the termination shall
be 100 Ω for 100 Ω and 120 Ω elements, and 150 Ω for 150 Ω elements. The nominal
common mode impedance shall be 50 Ω ± 25 Ω unless otherwise specified in the
measurement procedure.
NOTE The exact value of the common mode impedance is not critical for most measurements. Normally, a value
of 75 Ω is used for unscreened cabling while a value of 25 Ω is used for screened cabling.
Resistor loads shall use resistors specified for ± 1 % accuracy at d.c. and have a return loss
greater than 40 – 10log(f/100) where f is the frequency in megahertz (MHz). For pairs
connected to a balun, common mode load is implemented by applying a load at the centre tap
of the balun. The impedance of the load is equal to the common mode impedance. For pairs
connected to other kinds of balancing devices (180° power splitters), common mode load is
implemented by use of an attenuator at each of the balanced terminals of the balancing
device. This method is also used if the centre tap is not available at the balun used.

61935-1  IEC:2005 – 23 –
The attenuation provided by the attenuators shall be > 6 dB (see Figure 3). The common
mode impedance is approximately one quarter of the differential mode impedance for this
implementation. For pairs connected to resistor loads, common mode load is implemented by
the Y configuration shown in Figure 1.

R
R
R
IEC  1173/05
Figure 1 – Resistor load
R
dif
where R = (3)
R
dif
and R = R − (4)
2 com
where
R is the differential mode resistance (Ω);
dif
R is the common mode resistance (Ω).
com
For unscreened elements the common mode termination points for all pairs are connected
together at either end of the element. For screened elements, the common mode termination
points are connected to the cable screen or screens at each end of the element.
4.2.3 Reference loads for calibration
To perform a one or two-port calibration of the test equipment, a short circuit, an open circuit
and an impedance termination are required. These devices shall be used to obtain a
calibration at the reference plane.
The impedance termination shall be calibrated against a calibration reference, which shall be
a 50 Ω load, traceable to an international reference standard. If the value of the reference
load for calibration is 100 Ω, two loads in parallel shall be calibrated against the calibration
reference. If the value of the reference load for calibration is 150 Ω, three loads in parallel
shall be calibrated against the calibration reference. The reference loads for calibration shall
be placed in an N type connector according to IEC 60169-16, meant for panel mounting,
which is machined flat on the back side. The loads shall be fixed to the flat side of the
connector, distributed evenly around the centre conductor. A network analyser shall be
calibrated, one port full calibration, with the calibration reference. Thereafter, the return loss
of the reference loads for calibration shall be measured. The verified return loss shall be
>40 dB at the frequencies for which the measurements are to be carried out.
4.2.4 Test configurations
The cabling configurations that are tested in the field are as follows:
– Channel.
The channel test configuration is intended to be used by system designers and users of
data communication systems to verify the performance of the overall channel. The channel
as defined in ISO/IEC 11801 (or equivalent), includes the horizontal cable, a work area
equipment cord, a telecommunications outlet/connector, an optional transition connection

61935-1  IEC:2005 – 25 –
close to the work area and two cross-connect connections in the floor distributor. The total
length of work area, patch cords and jumpers shall not exceed 10 m. The connections to
the equipment at each end of the channel are not included in the channel definition. The
end-user patch cord shall be used to test channel performance.
– Permanent link.
The permanent link test configuration is intended to be used by installers and users of
data communication systems to verify the performance of permanently installed cabling.
The permanent link distributor as defined in ISO/IEC 11801 (or equivalent) consists of the
horizontal cabling and one connection at each end. The permanent link excludes both the
cable portion of the test cord of the test equipment and the connection to the test
equipment, but may include the optional transition point.
– CP Link.
The CP link test configuration is intended to be used by installers and users of data
communication systems to verify the portion of a permanent link between the floor
distributor and consolidation point.

Ref channel
Ref permanent link
Ref CP link
c c c T
c
E
CP TO wac
Eq cable pc
Floor distributor
IEC  1174/05
Key
Ref channel reference planes for channel
Ref permanent link reference planes for the permanent link
Ref CP link reference planes for the CP link
E equipment in floor distributor
c connection
T terminal equipment in work area
TO telecommunications outlet
CP consolidation point
Eq cable equipment cable
pc patch cord
wac work area cable
Figure 2 – Reference planes for permanent link and channel

61935-1  IEC:2005 – 27 –
The test configuration reference planes of a permanent link are at the end of the permanent
link test cords where the cable enters the body of the plug attached to the test cords at the
local end, and where the cable exits the body of the plug attached to the test cord at the
remote end, which each mate with the permanent link under test. Practically, the reference
plane of measurement should be within 50 mm from the reference plane definition when
making measurements on a permanent link. The test configuration reference plane of a
channel are at the end of the user patch cords where the cable enters the body of the plug
attached to the user patch cord at the local end, and where the cable exits the body of the
plug attached to the user patch cord at the remote end, which each mate with the channel
adapter. Practically, the reference plane of measurement should be within 50 mm of the
reference plane definition when making measurements on a channel.
4.2.5 Coaxial cables and test leads for network analysers
Coaxial cable assemblies between the network analyser and baluns should be as short as
possible. (It is recommended that they do not exceed 600 mm each). The baluns shall be
attached to a common ground plane.
Balanced test leads and associated connecting hardware to connect between the test
equipment and the cable assembly under test shall be taken from components that meet or
exceed the requirements for the category of the cable assembly under test. Balanced test
leads shall be limited to a length of 50 mm between each balun and the reference plane of the
element under test. Pairs shall remain twisted from the baluns to where connections are
made, and unscreened balanced test leads shall be separated by 5 mm from any ground
plane.
4.2.6 Balun requirements
Two classes of baluns with different performance levels are defined. This is in order to
facilitate measurements up to 1 GHz with commercially available baluns. The baluns may be
balun transformers or 180° hybrids with attenuators to improve matching if needed (see
Figure 3).
Att
180° splitter
To NWA
TP
Att
IEC  1175/05
Key
Att attenuator
180 ° splitter 180 degrees phase splitter
to NWA connection to network analyser
TP connections at test port
Figure 3 – 180° hybrid used as a balun

61935-1  IEC:2005 – 29 –
There are two class A balun requirements specified. class A-250 baluns are specified for
frequency response measurements up to 250 MHz; class A-600 baluns are specified for
frequency response measurements up to 600 MHz.
Class A baluns are preferred for the verifying of performance characteristics of all classes of
cabling.
Class B baluns may be used to verify performance of all classes of cabling provided that the
lower performance of the balun is taken into account in the measurement error calculation.
The specifications for classes A and B baluns apply for the whole frequency range for which
the balun is used. Baluns shall be RFI shielded and shall comply with the requirements given
in Table 1.
Table 1 – Test balun performance characteristics
Parameter Class A-250 value Class A-600 value Class B value
a
Impedance, primary 50 Ω unbalanced 50 Ω unbalanced 50 Ω unbalanced
d
Impedance, secondary Matched balanced Matched balanced Matched balanced
Insertion loss 3 dB maximum 3 dB maximum 10 dB maximum
Return loss secondary 20 dB minimum 12 dB minimum, 1 MHz - 15 MHz 6 dB minimum
20 dB minimum, 15 MHz - 550 MHz
17,5 dB minimum 550 MHz -600 MHz
Return loss, 10 dB minimum 15 dB minimum, 1 MHz - 15 MHz 10 dB minimum
b
Common mode 20 dB minimum, 15 MHz - 400 MHz
15 dB minimum, 400 MHz - 600 MHz
Power rating 0,1 W minimum 0,1 W minimum 0,1 W minimum
c
Longitudinal balance 60 dB minimum 60 dB minimum, 15 MHz - 350 MHz 35 dB minimum
50 dB minimum, 350 MHz – 600 MHz
c
Output signal balance 50 dB minimum 60 dB minimum, 15 MHz - 350 MHz 35 dB minimum
50 dB minimum, 350 MHz - 600 MHz
c
Common mode rejection 50 dB minimum 60 dB minimum, 15 MHz - 350 MHz 35 dB minimum
50 dB minimum, 350 MHz - 600 MHz
a
Primary impedance may differ, if necessary to accommodate analyser outputs other than 50 Ω.
b
Measured by connecting the balanced output terminals together and measuring the return loss. The
unbalanced balun input terminal shall be terminated by a 50 Ω load.
c
Measured per ITU-T Recommendations G.117 and O.9.
d
For 120 Ω cables, 120 Ω baluns will be used only in cases where it is requested by the user. Usually 100 Ω
baluns will be used.
Special guidelines for use of baluns:
NOTE 1 For best accuracy, the baluns should be supplied with connectors ( e.g. with IEC 60169-22 connectors).
NOTE 2 For tests up to 250 MHz, class A-250 baluns should be used.
NOTE 3 Class B baluns can be used in the whole frequency range for which their specifications apply, provided
their output signal balance is better than 50 dB below 100 MHz.
NOTE 4 For class B baluns there is a trade off between insertion loss and return loss. Return loss can be
improved by using an attenuator, which then increases insertion loss. If return loss is less than 10 dB, insertion
loss must be less than 5 dB. If insertion loss is higher than 5 dB, return loss must be higher than 10 dB.

61935-1  IEC:2005 – 31 –
4.2.7 Network analyser measurement precautions
To assure a high degree o
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