Structured Cabling
Structured Cabling is a set of standards that determine how to wire a data centre, office or building for data or voice communications, using Fibre Optic Cabling, Category 5 or Category 6 cable and RJ45 sockets. These standards define how to lay the cabling in a star formation, such that all outlets terminate at a central patch panel (which is normally 19 inch rack-mounted), from where it can be determined exactly how these connections will be used. Each outlet can be 'patched' into a data network switch (normally also rack mounted alongside), an IP telephone system or patched into a 'telecoms patch panel' which forms a bridge into a private branch exchange (PABX) telephone system, thus making the connection a voice port.
Experience Makes the Difference
Coupled with a detailed Assessment and Planning engagement, edi Communications can plan design and install a structured cabling system that will allow your business to communicate efficiently with a cable and fibre infrastructure required by today's networks.
edi Communications understands the high cost of physical plant change and implementation, and the challenges of effectively maintaining that physical plant for an increasingly mobile work force. Employee moves, adds, and changes can also be managed through this solution.
edi Communications broad experience in Cat 5e/6 cabling and fibre design and implementation can assist businesses in deciding the best investment of scarce IT resources into new infrastructures. Designs are consistent with today's business needs, characteristics, and requirements. Along with the information transfer needs of organizations, the solution incorporates planning, required facility modifications, installation planning and implementation, testing and certifications, and on-site support services.
Data Cabling
Cat 5, Cat 6 Cable
Today, your network cabling system carries the lifeblood of your organization - information. The installation, material, quality of cable and testing procedures are all much more critical in data wiring than in voice. The main reason for this is that networks today are designed to carry large amounts of information at incredible speeds. To accomplish this over unshielded twisted pair cable (UTP), many different criteria must be met.
Who sets the criteria and standards for network cabling? Well, the three major players are The Institute of Electrical and Electronics Engineers (IEEE - commonly called I-triple-E ) who work on developing new protocols, the American National Standards Institute (ANSI), and the Telecommunications Industry Association / Electronic Industry Alliance (TIA/EIA) who issue the standards and testing procedures.
Suffice it to say that these people have been busy over the past 12 years - as we've seen network speeds increase from 10 million bits of information per second, over Category 3 wire, back in 1991 to 1 billion bits (called Gigabit Ethernet) today. With bandwidth increasing and reliance on the network at an all time high, getting information to where it needs to be is becoming more challenging than ever. Ask any IT Manager what their most common network problem is and you will most likely hear them rant about cabling issues. In fact, cabling problems, which account for over 50% of network problems, cost companies millions annually. The most common problems are:
- Low attenuation
- Poor NEXT (near-end crosstalk)
- Poor ACR (attenuation-to-crosstalk ratio)
- Poor delay skew (data arrives at different times)
- Impedance
- Poor return loss (also known as "echo")
- Poor ELFEXT (equal-level far-end crosstalk) numbers for cable, connecting hardware and channel
- Splices in cable
- Mis-labelled cables
All of these problems can be avoided if the cabling is installed and tested properly. The cable must be installed following strict and specific guidelines and the testing must be done using the right equipment calibrated for the latest standards.
Category 5 Cable
Category 5 cable, commonly known as Cat 5, is an unshielded twisted pair cable type designed for high signal integrity. With the 2001 introduction of the TIA/EIA-568-B standard, the category 5 cabling specification was made obsolete and superseded by the category 5e specification. The original specification for category 5 cable was defined in ANSI/TIA/EIA-568-A, with clarification in TSB-95. These documents specified performance characteristics and test requirements for frequencies of up to 100 MHz. Cat 5 cable included four twisted pairs in a single cable jacket. It was most commonly used for 100Mbit/s networks, such as 100BASE-TX Ethernet, although IEEE 802.3ab defined standards for 1000BASE-T - gigabit Ethernet over Cat 5 cable. Cat 5 cable typically had three twists per inch of each twisted pair of 24 gauge copper wires within the cable. The twisting of the cable reduces electrical interference and crosstalk. Another important characteristic is that the wires are insulated with a plastic (FEP) that has low dispersion, that is, the dielectric constant of the plastic does not depend greatly on frequency. Special attention also has to be paid to minimizing impedance mismatches at connection points.
Cat 5 cables were often used in structured cabling for computer networks such as Fast Ethernet, although they were also used to carry many other signals such as basic voice services, token ring, and ATM (at up to 155 Mbit/s, over short distances).
Usage and wiring methods
Cat 5e cable is an enhanced version of Cat 5 that adds specifications for far-end crosstalk. Although 1000BASE-T was designed for use with Cat 5 cable, the tighter specifications associated with Cat 5e cable and connectors make it an excellent choice for use with 1000BASE-T. Despite the stricter performance specifications, Cat 5e cable does not enable longer cable distances for Ethernet networks: horizontal cables are still limited to a maximum of 90 m in length. Cat 5e cable performance characteristics and test methods are defined in TIA/EIA-568-B.2-2001.
Generally solid core cable is used for connecting between the wall socket and the socket in the patch panel whilst stranded cable is used for the patch leads between hub/switch and patch panel socket and between wall port and computer. Cable types, connector types and cabling topologies are defined by TIA/EIA-568-B. RJ-45 electrical connectors were nearly always used for connecting Cat 5 cable.
Category 6 Cable
Category 6 cable, commonly known as Cat 6, ANSI/TIA/EIA-568-B.2-1 is a cable standard for Gigabit Ethernet and other network protocols that is backward compatible with Cat 5/5e standards. Cat 6 features more stringent specifications for crosstalk and system noise. The cable standard is suitable for 10BASE-T / 100BASE-TX and 1000BASE-T (Gigabit Ethernet) connections. It provides performance of up to 250 MHz.
The cable contains four twisted copper wire pairs, just like earlier copper cable standards. While Cat 6 is sometimes made with 23 gauge wire, this is not a requirement; the ANSI/TIA-568-B.2-1 specification states the cable may be made with 22 to 24 gauge wire, so long as the cable meets the specified testing standards. When used as a patch cable, Cat 6 is normally terminated in RJ-45 electrical connectors. If components of the various cable standards are intermixed, the performance of the signal path will be limited to that of the lowest category. As with all cables defined by TIA/EIA-568-B, the maximum allowed length of a Cat 6 horizontal cable is 90 m. A complete channel (horizontal cable plus cords on either end) is allowed to be up to 100 m in length, depending upon the ratio of cord length: horizontal cable length.
| RJ-45 Wiring (TIA/EIA-568-B T568A) | RJ-45 Wiring (TIA/EIA-568-B T568B) | ||||||
|---|---|---|---|---|---|---|---|
| Pin | Pair | Wire | Colour | Pin | Pair | Wire | Colour |
| 1 | 3 | 1 | white/green | 1 | 2 | 1 | white/orange |
| 2 | 3 | 2 | green | 2 | 2 | 2 | orange |
| 3 | 2 | 1 | white/orange | 3 | 3 | 1 | white/green |
| 4 | 1 | 2 | blue | 4 | 1 | 2 | blue |
| 5 | 1 | 1 | white/blue | 5 | 1 | 1 | white/blue |
| 6 | 2 | 2 | orange | 6 | 3 | 2 | green |
| 7 | 4 | 1 | white/brown | 7 | 4 | 1 | white/brown |
| 8 | 4 | 2 | brown | 8 | 4 | 2 | brown |
Category 7 Cable
Category 7 cable, commonly known as Cat 7 (ISO/IEC 11801:2002 category 7/class F), is a cable standard for Ethernet and other interconnect technologies that can be made to be backwards compatible with traditional Cat 5 and Cat 6 Ethernet cable. Cat 7 features even more stringent specifications for crosstalk and system noise than Cat 6. To achieve this, shielding has been added for individual wire pairs and the cable as a whole.
The CAT7 cable standard has been created to allow 10-gigabit Ethernet over 100 meters of copper cabling. The cable contains four twisted copper wire pairs, just like the earlier standards. CAT7 can be terminated either with RJ-45 compatible GG45 electrical connectors which incorporate the RJ-45 standard. When combined with GG-45 connectors, CAT7 cable is rated for transmission frequencies of up to 600 MHz. When combined with TERA connectors, CAT7 cable is rated for transmission frequencies above 600 MHz.
Fibre Optic Cabling
Fibre Optic cabling provides a far greater bandwidth than copper and is typically used for backbone connection between localized networking equipment and is increasingly becoming the preferred choice for high quality and reliable analogue and digital communications.
Although its higher cost can be prohibitive for desktop applications, fibre optic cabling provides a high security link, with immunity from electromagnetic interference (EMI). It is also the solution for inter-building links and other connections beyond the maximum 90m for Cat 5e or Cat 6 copper cabling.
Fibre Optic Cable Design & Installation
edi Communications carries out the design, installation, testing & maintenance of Fibre Optic systems, both internal & external work including repair work.
All types of fibre optic cabling systems are offered including:
- Multimode 62.5/125 (OM1) Datacomms
- Multimode 50/125 (OM2) Video & Datacomms Systems
- Multimode 50/125 (OM3) Gigabit Ethernet an 10 Gig Ethernet for up to 300m
- Singlemode 8/125 (OS1) Gigabit Ethernet and 10 Gig Ethernet for up to 2km.
- All cables are internal/external grade.
Shielded Cable
A shielded cable is an electrical cable of one or more insulated conductors enclosed by a shield that may be composed of braided strands of copper (or other metal), a non-braided spiral winding of copper, or a layer of metal tape. Usually, this shield is covered with another layer of inexpensive insulation. The shield acts as a Faraday cage to prevent electrical noise from affecting the signals, and to prevent electromagnetic radiation that may interfere with other devices.
In single conductor cables the shield usually acts as the return path for the signal and is usually connected to the circuit reference point. In multi conductor cables the shield will be grounded, often only at one end, and doesn't carry circuit current.
High voltage power cables shields balance the stress on their electrical insulation and are earthed to pass any fault current back to the source. Termination of the HV shields during cable installation is of great importance to prevent hazards while minimizing undesired electrical signals or currents.
T568A and T568B Termination
Perhaps the widest known and most discussed feature of TIA/EIA-568-B.1-2001 is the definition of pin/pair assignments for eight-conductor 100-ohm balanced twisted-pair cabling, such as Category 3, Category 5 and Category 6 unshielded twisted-pair (UTP) cables. These assignments are named T568A and T568B and they define the pinout, or order of connections, for wires in RJ-45 eight-pin modular connector plugs and jacks. Although these definitions consume only one of the 468 pages in the standards documents, a disproportionate amount of attention is paid to them. This is because cables that are terminated with differing standards on each end will not function normally.
TIA/EIA-568-B specifies that horizontal cables should be terminated using the T568A pin/pair assignments, "or, optionally, per [T568B] if necessary to accommodate certain 8-pin cabling systems." Despite this instruction, many organizations continue to implement T568B for various reasons, chiefly associated with tradition (T568B is equivalent to AT&T 258A). The United States National Communication Systems Federal Telecommunications Recommendations do not recognize T568B.
The primary colour of pair one is blue, pair two is orange, pair three is green and pair four is brown. Each pair consists of one conductor of solid colour, and a second conductor of the same colour with a white stripe. The specific assignments of pairs to connector pins varies between the T568A and T568B standards.
Mixing T568A-terminated patch cords with T568B-terminated horizontal cables (or the reverse) does not produce pinout problems in a facility. Although it may very slightly degrade signal quality, this effect is marginal and certainly no greater than that produced by mixing cable brands in-channel.
Wiring
Regardless of the wiring standard, RJ-45 modular jack pins are numbered 1 through 8, pin 1 being the leftmost pin on the connector side of the plug, 8 the rightmost. Pins on jacks are numbered correspondingly, pin 1 being the rightmost and pin 8 the leftmost connector when the connectors are on the bottom side of the socket.
The assignments of wire pairs to plug and jack pins are as follows:
| RJ-45 Wiring (TIA/EIA-568-B T568A) | ||||||
|---|---|---|---|---|---|---|
| Pin | T 568A Pair | T 568B Pair | Wire | T 568A Colour | T 568B Colour | Pins on plug face (jack is reversed) |
| 1 | 3 | 2 | tip |  White/Green stripe |  White/Orange stripe |  |
| 2 | 3 | 2 | ring |  Green solid |  Orange solid | |
| 3 | 2 | 3 | tip | White/Orange stripe | White/Green stripe | |
| 4 | 1 | 1 | ring |  Blue solid | Blue solid | |
| 5 | 1 | 1 | tip |  White/Blue stripe | White/Blue stripe | |
| 6 | 2 | 3 | ring | Orange Solid | Green solid | |
| 7 | 4 | 4 | tip |  White/Brown Stripe | White/Brown Stripe | |
| 8 | 4 | 4 | tip |  Brown Solid | Brown Solid | |
Note that the only difference between T568A and T568B is that pairs 2 and 3 (orange and green) are swapped. Both standards wire the pins "straight through", i.e., pins 1 through 8 on one end are connected to pins 1 through 8 on the other end. Also, the same sets of pins are paired in both standards: pins 1 and 2 form a pair, as do 3 and 6, 4 and 5 and 7 and 8. And although many cables implement some small electrical differences between pairs, these effects are negligible, so cables wired to either standard are interchangeable.
Backwards Compatibility
Because pair 1 connects to the centre pins (4 and 5) of the RJ-45 jack in both T568A and T568B, both standards are compatible with the first line of RJ-11, RJ-14, RJ-25 and RJ-61 connectors that all have the first pair in the centre pins of these connectors.
If the second line of a RJ-14, RJ-25 or RJ-61 plug is used, it connects to pair 2 (orange/white) of jacks wired to T568A but to pair 3 (green/white) in jacks wired to T568B. This makes T568B potentially confusing in telephone applications.
Because of different pin pairings, the RJ-25 and RJ-61 plugs cannot pick up lines 3 or 4 from either T568A or T568B without splitting pairs. This would most likely result in unacceptable levels of hum, crosstalk and noise. Because 10BASE-T and 100BASE-TX use only pairs 2 and 3, pairs 1 and 4 need not even be present in the cable. It is also common in some networks to use one 4-pair Category 5 cable to provide two separate 10BASE-T or 100BASE-TX links, assigning only two pairs to each link. However, such jacks cannot be used with 1000BASE-T as it requires all four pairs for each link. They are also incompatible with direct use by single-line telephones with standard RJ-11 plugs as nothing is connected to pair 1 in the jack. However, a separate telephone line could be connected to pair 1, thus allowing a single jack to be used for either voice or Ethernet without reconfiguration.