I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n

ITU-T L.76
TELECOMMUNICATION
STANDARDIZATION SECTOR
OF ITU
(05/2008)

SERIES L: CONSTRUCTION, INSTALLATION AND
PROTECTION OF CABLES AND OTHER ELEMENTS OF
OUTSIDE PLANT


Copper loop requirements for various
technologies including indoor and structured
cabling

Recommendation ITU-T L.76







Rec. ITU-T L.76 (05/2008) i
Recommendation ITU-T L.76
Copper loop requirements for various technologies including
indoor and structured cabling



Summary
Old indoor installations, designed for voice transmission, are responsible for intermittent faults and
performance degradation, in terms of throughput, when they are used for broadband applications.
Very often, the use of older cabling becomes impractical for today's needs. Structured cabling is a
solution that allows reliable broadband transmission and accommodates the increasingly varied
information and communication services, such as super-high speed internet, video-communication,
voice over Internet protocol (VoIP), Video on Demand (VoD), Internet protocol television (IPTV),
security, telemetry, etc.
General customer premises and residential buildings cabling architectures are introduced. Pertinent
electrical parameters and requirements are referred to in [ISO/IEC 11801] and [ITU-T L.75].
The purposes of Recommendation ITU-T L.76 are:
to present general indoor network architectures;
to recommend structured cabling as a solution for indoor network implementations; and
to define the requirements to indoor copper networks.


Source
Recommendation ITU-T L.76 was approved on 29 May 2008 by ITU-T Study Group 6 (2005-2008)
under Recommendation ITU-T A.8 procedure.


Keywords
General customer premises and residential buildings cabling, indoor copper cabling requirements,
structured cabling.


ii Rec. ITU-T L.76 (05/2008)
FOREWORD
The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
telecommunications, information and communication technologies (ICTs). The ITU Telecommunication
Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical,
operating and tariff questions and issuing Recommendations on them with a view to standardizing
telecommunications on a worldwide basis.
The World Telecommunication Standardization Assembly (WTSA), which meets every four years,
establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on
these topics.
The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
In some areas of information technology which fall within ITU-T's purview, the necessary standards are
prepared on a collaborative basis with ISO and IEC.



NOTE
In this Recommendation, the expression "Administration" is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain
mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the
Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some
other obligatory language such as "must" and the negative equivalents are used to express requirements. The
use of such words does not suggest that compliance with the Recommendation is required of any party.




INTELLECTUAL PROPERTY RIGHTS
ITU draws attention to the possibility that the practice or implementation of this Recommendation may
involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence,
validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others
outside of the Recommendation development process.
As of the date of approval of this Recommendation, ITU had not received notice of intellectual property,
protected by patents, which may be required to implement this Recommendation. However, implementers
are cautioned that this may not represent the latest information and are therefore strongly urged to consult the
TSB patent database at http://www.itu.int/ITU-T/ipr/.



ITU 2009
All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the
prior written permission of ITU.

Rec. ITU-T L.76 (05/2008) iii
CONTENTS
Page
1 Scope ............................................................................................................................ 1
2 References..................................................................................................................... 1
3 Definitions .................................................................................................................... 1
4 Abbreviations and acronyms ........................................................................................ 2
5 Conventions .................................................................................................................. 3
6 Generic cabling system for customer premises ............................................................ 3
6.1 Structure of generic cabling for building telecommunication facilities ......... 3
6.2 Campus backbone cabling subsystem............................................................ 3
6.3 Building backbone cabling subsystem........................................................... 3
6.4 Horizontal cabling subsystem......................................................................... 3
6.5 Design objectives............................................................................................ 4
7 Residential area telecommunication cabling ................................................................ 4
7.1 Principles ........................................................................................................ 4
7.2 Multi-tenant unit/apartment cabling system................................................... 4
7.3 Single residential unit cabling system............................................................ 5
8 Requirements ................................................................................................................ 6
8.1 Performance of balanced cabling ................................................................... 6
Bibliography............................................................................................................................. 8





Rec. ITU-T L.76 (05/2008) 1
Recommendation ITU-T L.76
Copper loop requirements for various technologies including
indoor and structured cabling
1 Scope
The purposes of this Recommendation are:
to present general indoor network architectures;
to recommend structured cabling as a solution for indoor network implementations; and
to define the requirements for indoor copper networks.
2 References
The following ITU-T Recommendations and other references contain provisions which, through
reference in this text, constitute provisions of this Recommendation. At the time of publication, the
editions indicated were valid. All Recommendations and other references are subject to revision;
users of this Recommendation are therefore encouraged to investigate the possibility of applying the
most recent edition of the Recommendations and other references listed below. A list of the
currently valid ITU-T Recommendations is regularly published. The reference to a document within
this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
[ITU-T L.75] Recommendation ITU-T L.75 (2008), Test, acceptance and maintenance
methods of copper subscriber pairs.
[ISO/IEC 11801] ISO/IEC 11801:2002, Information technology Generic cabling for customer
premises.
<http://www.iso.org/iso/iso_catalogue_tc/catalogue_detail.htm?csnumber=36491>
3 Definitions
This Recommendation defines the following terms (aligned with [ISO/IEC 11801]):
3.1 balanced cable: Cable consisting of one or more metallic symmetrical cable elements
(twisted pairs or quads).
3.2 building backbone cabling subsystem: Distribution system connecting the main
distribution frame to an intermediate distribution frame, an intermediate distribution box, a floor
distribution frame or a floor distribution box in a building and the distribution system
interconnecting intermediate distribution frames in a building.
3.3 building distribution frame (or box): Distribution frame (or box) installed in each
multi-tenant unit for effective building wire management in case of a configuration of a residential
complex of more than two multi-tenant units.
3.4 cabling: System of telecommunication cables, cords and connecting hardware that can
support the connection of information technology equipment.
3.5 campus: Premise containing one or more buildings.
3.6 campus backbone cabling subsystem: Distribution system connecting the main
distribution frame or the main distribution box in a local area to a building distribution frame or a
building distribution box, and the distribution system interconnecting building distribution frames.
3.7 consolidation point (CP): Connection point in the horizontal cabling subsystem between a
floor distributor and a telecommunications outlet.

2 Rec. ITU-T L.76 (05/2008)
3.8 connecting hardware: Connecting hardware is considered to consist of a device or a
combination of devices used to connect cables or cable elements.
3.9 cross-connect: Apparatus enabling the termination of cable elements and their
cross-connection, primarily by means of patch cords or jumpers.
3.10 customer device box: Distribution box installed in a private space of a user for effective
distribution of telecommunication line or the line for cable television facilities, etc.
3.11 demarcation point: Boundary point between a commercial facility and user facility.
3.12 main distribution box: Network connection facility which interconnects a carrier's facility
with a user's facility in a small building which accommodates below 300 office lines, as in a single
residential unit, and which is installed at a demarcation point for satisfactory cross-connection and
maintenance of the line.
3.13 main distribution frame: Network connection facility which interconnects a carrier's
facility with a user's facility in a big building which accommodates over 300 office lines, as in a
multi-tenant unit, and which is installed instead of a main distribution box at a demarcation point
for satisfactory cross-connection and maintenance of the line.
3.14 patch cord: Cable, cable unit or cable element with connector(s) used to establish
connections on a patch panel.
3.15 patch panel: Assembly of multiple connectors designed to accommodate the use of patch
cords.
4 Abbreviations and acronyms
This Recommendation uses the following abbreviations and acronyms:
ACR Attenuation to Crosstalk Ratio
BD Building Distributor
CD Campus Distributor
CP Consolidation Point
DSLAM Digital Subscriber Line Access Multiplexer
EQP Equipment
ELFEXT Equal Level Far-End CrossTalk
FD Floor Distributor
FEXT Far-End CrossTalk
IPTV Internet Protocol Television
NEXT Near-End CrossTalk
PS ELFEXT Power Sum Equal Level Far-End CrossTalk
PS NEXT Power Sum Near-End CrossTalk
TO Telecommunication Outlet
UTP Unshielded Twisted Pair
VoD Video on Demand
VoIP Voice over Internet Protocol
xDSL Generic Digital Subscriber Line

Rec. ITU-T L.76 (05/2008) 3
5 Conventions
None.
6 Generic cabling system for customer premises
6.1 Structure of generic cabling for building telecommunication facilities
Generic cabling systems contain up to three cabling subsystems: campus backbone, building
backbone and horizontal cabling. The cabling subsystems are connected together to create a generic
cabling system with a structure as shown in Figure 6-1. The distributors provide the means to
configure the cabling to support different topologies such as bus, star and ring. In case of a
hierarchical structure of the interconnection of subsystems, refer to [ISO/IEC 11801].

Figure 6-1 General cabling structure
6.2 Campus backbone cabling subsystem
The campus backbone cabling subsystem extends from the campus distributor (CD) to the building
distributor(s) (BD), usually located in separate buildings. When present, the subsystem includes the
campus backbone cables, any cabling components within the building entrance facilities, jumpers
and patch cords in the campus distributor, and the connecting hardware on which the campus
backbone cables are terminated (at both the campus and building distributors).
6.3 Building backbone cabling subsystem
The building backbone cabling subsystem extends from building distributor(s) to the floor
distributor(s) (FD). When present, the subsystem includes the building backbone cables, jumpers
and patch cords in the building distributor, and the connecting hardware on which the building
backbone cables are terminated (at both the building and floor distributors).
6.4 Horizontal cabling subsystem
The horizontal cabling subsystem extends from a floor distributor to the telecommunication
outlet(s) connected to it. The subsystem includes the horizontal cables, jumpers and patch cords in
the floor distributor, the mechanical termination of the horizontal cables at the telecommunication
outlet, the mechanical termination of the horizontal cables at the floor distributor including the
connecting hardware, a consolidation point (optional) and the telecommunication outlets.

4 Rec. ITU-T L.76 (05/2008)
6.5 Design objectives
Horizontal cabling should be designed to support the broadcast set of existing and emerging
applications and therefore provide the longest operational life. This will minimize disruption and
the high cost of re-cabling in the work area.
Building backbone cabling should be designed for the entire life of the generic cabling system.
However, it is common to adopt short-term approaches that support current and foreseeable
application requirements, particularly where there is no good physical access to pathways. The
selection of campus backbone cabling may require a longer-term approach than that adopted for the
building backbone, particularly if access to pathways is more limited.
7 Residential area telecommunication cabling
7.1 Principles
In case of a multi-tenant unit, a customer device box for each household or a connection
point with the function of a customer device box should be installed in each user's private
space.
In case of a single residential area unit, a customer device box should be installed at a
demarcation point instead of a main distribution box.
At least more than one telecommunication outlet should be installed from a customer
device box to each room, and four pairs of UTP cables or equivalent to that or more should
be installed in star wiring topology from a customer device box to each telecommunication
outlet. However, a voice-only service is an exception and does not follow this principle.
In lead-in line for each household, UTP cable with at least more than four pairs should be
led in, and more than eight pairs is recommended.
Cabling in a building should be done using the star wiring topology, and careful
consideration for installation of building telecommunication facilities should be made when
designing so that it can accommodate various information and communication services
permanently.
7.2 Multi-tenant unit/apartment cabling system
At a demarcation point, the main distribution box or the main distribution frame is installed as user
network connection equipment. The section from the main distribution box or the main distribution
frame to a building distribution frame is called the campus backbone cabling subsystem, and the
section from a building distribution frame to an intermediate distribution frame is called the
building backbone cabling subsystem, and the section from an intermediate distribution frame to a
customer device box, or the telecommunication outlet, is called the horizontal cabling subsystem.
In a case where a residential complex of over two multi-tenant units are configured, the main
distribution box is installed in any one place within the multi-tenant unit, and then the office line is
led in. Backbone cables are distributed to each customer device box of other multi-tenant units
through a building distribution frame (a building distribution box) or an intermediate distribution
frame. Cabling equipment and material for each building cabling subsystem are selected in
consideration of building usage, telecommunication accommodation facilities, application facilities,
etc. Figure 7-1 shows the building cabling system of a multi-tenant unit.
Cross connection of a campus backbone cabling subsystem is done in the main telecommunication
room and in each building telecommunication room. In a campus backbone cabling subsystem,
cables from the telecommunication room are led into each multi-tenant building (apartment block,
etc.) through a tray facility of underground conduit located in an underground vault or parking lot
facility of the apartment block. In campus backbone cabling subsystems, cables can be isolated
from power cables to prevent power induction.

Rec. ITU-T L.76 (05/2008) 5
A building cable is classified into a backbone cable (a campus backbone cable, a building backbone
cable) and a horizontal cable. Backbone and horizontal cables should not be damaged due to
excessive tensile forces being applied during or after installation. The tensile force that is applied to
a four-pair cable in order to minimize cable sag should not exceed 10 kg (100 N), nor exceed the
manufacturer's specification for the tensile strength of a backbone or horizontal cable. To prevent
electrical interference in the case where a long section has to be installed, a cable cannot be installed
with a power cable in parallel. An outdoor cable should be used when installing outside, including
the campus backbone cable. The stipulated connecting accessories should be used for cable
connection. The unconnected insulated conductor should be protected with extra length as a
contingency for the future.

Figure 7-1 Illustration of the building cabling system for apartments
7.3 Single residential unit cabling system
At the demarcation point of a single residential unit, a customer device box (if necessary, with
protector) should be installed. In the case of a building cabling system of a single residential unit,
refer to multi-tenant unit. A building cabling of a single residential unit is shown in Figure 7-2.

6 Rec. ITU-T L.76 (05/2008)

Figure 7-2 Illustration of the building cabling of a single residential unit
8 Requirements
Indoor installations are, for the purposes of requirement definition, divided in two segments:
cabling before the modem input and cabling after the modem output.
For the first segment, test procedures and requirements are recommended to be evaluated in the
same way as defined in [ITU-T L.75] because, from the DSLAM up to each modem, signals
transmitted and received follow one of the xDSL standards.
For the segment after the modem, field testing for class A to F should be conducted according to
clause 6.4 (balanced cabling performance) of [ISO/IEC 11801].
The parameters specified in this clause apply to channels with screened or unscreened cable
elements, with or without overall screen, unless explicitly stated otherwise.
The nominal impedance of channels is 100 . This is achieved by suitable design and appropriate
choice of cabling components (irrespective of nominal impedance).
8.1 Performance of balanced cabling
8.1.1 General
The performance of balanced cabling, balanced cords and connecting hardware requirements are
described in [ISO/IEC 11801]. For convenience, some of the contents are summarized here.
The performance of balanced cabling is specified for channels, permanent links and CP links
(see Figure 8-1).

Rec. ITU-T L.76 (05/2008) 7

Figure 8-1 Channel, permanent link and CP link of a balanced cabling
8.1.2 Classification of balanced cabling
The following classes for balanced cabling are defined according to [ISO/IEC 11801].
Class A is specified up to 100 kHz.
Class B is specified up to 1 MHz.
Class C is specified up to 16 MHz.
Class D is specified up to 100 MHz.
Class E is specified up to 250 MHz.
Class F is specified up to 600 MHz.
A class A channel is to provide at least the minimum transmission function to support class A
application. Similarly, class B, C, D, E and F channels provide the transmission performance to
support class B, C, D, E and F applications, respectively. Links and channels of a given class will
support all application of a lower class. Class A is regarded as the lowest class.
Channels, permanent links and CP links in the horizontal cabling shall be installed to provide a
minimum of class D performance.
Cables and connecting hardware of different categories may be mixed within a channel. However,
the resultant cabling performance will be determined by the category of the lowest performing
component.
The selection of balanced cabling component will be determined by the class of applications to be
supported. For examples;
Category 5 components provide class D balanced cabling performance.
Category 6 and 6A components provide class E balanced cabling performance.
Category 7 components provide class F balanced cabling performance.
In case of applications by classes, refer to Annex F in [ISO/IEC 11801].

8 Rec. ITU-T L.76 (05/2008)
Bibliography

[b-ITU-T G.996.1] Recommendation ITU-T G.996.1 (2001), Test procedures for digital
subscriber line (DSL) transceivers.
[b-ITU-T L.19] Recommendation ITU-T L.19 (2003), Multi-pair copper network cable
supporting shared multiple services such as POTS, ISDN and xDSL.



Printed in Switzerland
Geneva, 2009
SERIES OF ITU-T RECOMMENDATIONS
Series A Organization of the work of ITU-T
Series D General tariff principles
Series E Overall network operation, telephone service, service operation and human factors
Series F Non-telephone telecommunication services
Series G Transmission systems and media, digital systems and networks
Series H Audiovisual and multimedia systems
Series I Integrated services digital network
Series J Cable networks and transmission of television, sound programme and other multimedia signals
Series K Protection against interference
Series L Construction, installation and protection of cables and other elements of outside plant
Series M Telecommunication management, including TMN and network maintenance
Series N Maintenance: international sound programme and television transmission circuits
Series O Specifications of measuring equipment
Series P Telephone transmission quality, telephone installations, local line networks
Series Q Switching and signalling
Series R Telegraph transmission
Series S Telegraph services terminal equipment
Series T Terminals for telematic services
Series U Telegraph switching
Series V Data communication over the telephone network
Series X Data networks, open system communications and security
Series Y Global information infrastructure, Internet protocol aspects and next-generation networks
Series Z Languages and general software aspects for telecommunication systems