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Structured Cabling Installation Practices - Twisted Pair Cabling

​Welcome to the start of our new series on Structured Cable Installation Practices. This first article provides an overview of twisted pair cabling and how it works; the different types of twisted pair cabling; and information on cabling standards.

Twisted pair cable is a type of cabling that is used for most modern Ethernet networks and telephone communications. The twisted pair cable is basically two conductors which are wound together to form a circuit that can transmit data, while also providing protection against crosstalk, being the noise generated by adjacent pairs.​

Twisting wires decreases interference because the loop area between the wires (which determines the magnetic coupling into the signal) is reduced. In balanced pair operation, the two wires typically carry equal and opposite signals (differential mode) which are combined by addition at the destination. The common mode noise from the two wires (mostly) cancel each other in this addition because the two wires have similar amounts of electromagnetic interference (EMI) that are 180 degrees out of phase. This results in the same effect as subtraction. Differential mode also reduces electromagnetic radiation from the cable, along with the attenuation that it causes.

The twist rate (also called pitch of the twist, usually defined in twists per meter) makes up part of the specification for a given type of cable. Where pairs are not twisted, one member of the pair may be closer to the source than the other, and thus exposed to slightly different induced electromotive force (EMF).

Where twist rates are equal, the same conductors of different pairs may repeatedly lie next to each other, partially undoing the benefits of differential mode. For this reason, it is commonly specified that, at least for cables containing small numbers of pairs, the twist rates must differ.

Normally wire pair cables cannot carry high bandwidth signals fast enough for LAN communications. The wires also radiate like antennas, so they interfere with other electronic devices. However, two developments allowed use of simple wire for high speed signals.

The first development is using twisted pair cables. The two conductors are tightly twisted (1-3 twists per inch) to couple the signals into the pair of wires. Each pair of wires is twisted at different rates to minimize cross-coupling. Then, "balanced transmission" is used to minimize electromagnetic emissions. Balanced transmission works by sending equal but opposite signals down each wire of the pair. The receiving end looks at each wire and sees a signal of twice the amplitude carried by either wire. While each wire radiates energy, they carry the opposite polarity signal, so the two wires cancel out the radiated signals and reduce interference.

Using these techniques and having two pair of wires sending signals in opposite directions, has made it possible to adapt unshielded twisted pair (UTP) cables to work with high speed Ethernet networks. A direction to allow operation within networks of over 1000 megabits per second.

Color Coding 

Ethernet cable color-coding exists as part of the industry standard - T568A and T458B. It allows cabling technicians to reliably predict how the ethernet cable is terminated on both ends so they can follow other technicians' work without having to guess or spend time deciphering the function and connections of each wire pair. There is no electrical difference between the T568A and T568B wire sequences, so neither is inherently superior.

The only difference between them is how frequently they are used in a particular region or type of organization. So, your choice of color code - which one is "right" - will largely depend on the country you work in and what types of organizations you install for. Which one should I use? Either standard is acceptable in most cases. You can use either one as long as you're consistent. When entering a new job, you may want to take a look at any pre-existing cabling to see which standard is already in use at that location. T568A is the majority standard followed in European and Pacific countries. It is also used in all United States government installations. T568B is the standard followed by the majority of Ethernet installations in the United States for RJ45 color code. It is the more common standard used when cabling for businesses.

Classes and Categories

Above is an overview of the different UTP categories that are available today, along with their specifications and application. All of the categories listed are network wire specifications for twisted pair cabling which support computer network and telephone traffic. Category 5e has more twists per inch than Category 3, therefore can run at higher speeds and greater lengths. As mentioned earlier, the twist effect of each pair in the cables ensures any interference picked up on one cable is cancelled out by the cable's partner which twists around the initial cable.

Category 6 wire was originally designed to support gigabit Ethernet, although there are standards that will allow gigabit transmission over Category 5e wire. It is similar to Category 5e wire but contains a physical separator between the four pairs to further reduce electromagnetic interference. Category 6 is able to support speeds of 1Gbps for lengths of up to 100 meters, and 10Gbps is also supported for lengths of up to 55 meters.

Today, most new cabling installations use Category 6 as a standard, however it is important to note that all cabling components (jacks, patch panels, patch cords etc) must be Category 6 certified and extra caution must be given to the proper termination of the cable ends.

Category 7 is a newer copper cable specification designed to support speeds of 10Gbps at lengths of up to 100 meters. To achieve this, the cable features four individually shielded pairs plus an additional cable shield to protect the signals from crosstalk and electromagnetic interference (EMI).

Due to the extremely high data rates, all components used throughout the installation of a Category 7 cabling infrastructure must be CAT7 certified. Failing to use CAT7 certified components will result in the overall performance degradation and failure of any CAT7 certification tests (e.g using a Cable Analyzer) since CAT7 performance standards are most likely not to be met. Today, CAT7 is usually used in DataCenters for backbone connections between servers, network switches and storage devices.

DINTEK offers cabling solutions in Category 5e, Category 6Category 6A, Category 7 & Category 8 with all products within these ranges having been independently certified.


Standards

Structured cabling design and installation is governed by a set of Standards that define how to lay the cabling in various topologies in order to meet the needs of the customer. This published document sets out specifications and procedures designed to ensure that a material, product, method or service is fit for its purpose and consistently performs in the way it was intended.

ANSI/TIA-568-A, the Commercial Building Cabling Standard, was first ratified in 1991, and its publication revolutionized the industry. Its purpose was to specify a structured cabling system that would provide a minimum level of performance, support a multi-vendor environment, provide direction for the design of telecommunications equipment and cabling products and establish performance and technical criteria for various types of cable and connecting hardware. The goal was to specify a structured cabling system with a projected usable life of at least 10 years.

The Commercial Building Cabling Standard is, like all standards, voluntary. However, end users and network designers like to have a standards-compliant structured cabling system; it provides a known quantity that they can count on and it helps to ensure that they have a system that is robust and reliable. Most Standards in the telecommunications industry are voluntary and consensus based.

Standards Organizations 

ISO (International Standardization Organization) is the main international telecommunications systems standards organization. IEC (International Electro technical Commission) is an organization that certifies component parts for electrical performance. Along with the ISO, the IEC developed the ISO/IEC 11801 (Generic cabling for customer premises) standard.

CENELEC (European Committee for Electro technical Standardization) developed the ENS0173 standard used throughout parts of Europe - they basically regionalized the ISO/IEC 11801 standard.
AS/NZS (Australian/New Zealand Standard) developed a similar standard, called the AZ/NZS 3080.

CSA (Canadian Standards Association) developed the CSA T529, a similar standard to the ISO/IEC 11801, used throughout Canada.
ANSI (American National Standards Institute) is an organization that has other organizations and standards bodies reporting to and through it, including TIA (Telecommunications Industry Association) and EIA (Electronic Industries Association).

The TIA and ANSI have joined forces to develop communications standards for commercial premises, including the ANSI/TIA-568.D, (Commercial Building Telecommunications Cabling Standard), which is similar in scope to the ISO/IEC 11801.
There are some additional standards under ANSI/TIA, ISO, EN, AS/NZS, and CSA: The ANSI/TIA, the AS 3084 and the CSA-530, respectively, are standards that govern Pathways and Spaces for Premises Cabling and the ANSI/TIA -606, AS/NZS 3085, and CSA-529 are standards that govern labeling.

Networking Standards 

The ISO/IEC 11801 is the generic Standard for Cabling for Customer Premises and its purpose is to provide a world standard for the design, installation, and administration of commercial building telecommunications systems. All other standards that follow have adapted the ISO/IEC-11801 to their particular regions.

ANSI/TIA-568-D is the latest generic Telecommunications Cabling Standard and was originally published as ANSI/TIA-568 in 1991. The ANSI/TIA-568-D set of Standards is set to enable the planning and installation of a structured cabling system for commercial buildings, specifying a generic telecommunications cabling system that will support a multi-product, multi-vendor environment. In other words, to provide a common baseline for the design and installation of telecommunications cables and connecting hardware in commercial buildings. This family of Standards contains the following main documents:

ANSI/TIA-568.0-D - Generic Telecommunications Cabling for Customer Premises
ANSI/TIA-568.1-D - Commercial Building Telecommunications Cabling Standard
ANSI/TIA-568.2-D - Balanced Twisted-Pair Telecommunication Cabling and Components Standard
ANSI/TIA-568.3-D - Optical Fiber Cabling Components Standard

 Key updates and changes to the '568-D documents include:

  • Generic terminology has been introduced to describe cabling segments and connection points
  • Category 6A has been added as a recognized media
  • Optical fiber link test requirements were moved to this document
  • Optical fiber link performance requirements were moved to this document
  • The installation bend radius requirement for UTP and F/UTP cables has changed to "4x cable o/d" and the patch cord bend radius requirement has changed to "1x cable o/d" to accommodate larger diameter cables.

​ANSI/TIA-569-B is the Commercial Building Standard for Telecommunication Pathways and Spaces and its purpose is to standardize specific design and construction practices within and between buildings, which are in support of telecommunications media and equipment. Basically, the ANSI/TIA-569B Standard covers the pathways (how cables get from one area to another) and spaces (the locations of telecommunications equipment and terminations) and how they should be designed and utilized within the telecommunications infrastructure.

ANSI/TIA-569-C also includes items and appendices on grounding and bonding, miscellaneous pathways, electromagnetic interference (EMI) concerns, symbols and fire stopping.

ANSI/TIA-606-B is the Administration Standard for the Telecommunications Infrastructure of Commercial Buildings and its purpose is to provide a uniform administration scheme that is independent of applications, and establishes guidelines for owners, end users, manufacturers, consultants, contractors, designers, installers, and facilities administrators involved in the administration (and labeling) of Telecommunications infrastructure.

ANSI/TIA-607-B is the Commercial Building Standard for Grounding and Bonding Requirements for the Telecommunications Industry. Its purpose is to enable the planning, design and installation of a telecommunications grounding system with or without prior knowledge of the telecommunications systems that will be subsequently installed.

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