Cat 5

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Category 5
Category 5e
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Category 5 cable is a twisted pair high signal integrity cable type often referred to as Cat5 or Cat-5. Most cables are unshielded, relying on the twisted pair design for noise rejection, and some are shielded. Category 5 has been superseded by the Category 5e specification structured cabling for computer networks such as Ethernet, and is also used to carry many other signals such as basic voice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).

Category 5

The specification for Category 5 cable was defined in American National Standards Institute 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.

Category 5 cable includes twisted pairs in a single cable jacket. This use of balanced lines helps preserve a high signal-to-noise ratio despite interference from both external sources and other pairs (this latter form of interference is called crosstalk). It is most commonly used for 100 Mbit/s networks, such as 100BASE-TX Ethernet, although IEEE 802.3ab defines standards for 1000BASE-T – Gigabit Ethernet over category 5 cable. Cat 5 cable typically has three twists per inch of each twisted pair of 24 American wire gauge (AWG) copper wires within the cables.


Solid core Cable vs Stranded Cable

Solid core cable is cheaper and is supposed to be used for long permanently installed runs. It is less flexible than stranded and more prone to failure if repeatedly flexed. Stranded cable is used for fly leads at patch panel and for connections from wall-ports to end devices, as it resists cracking of the conductors. Stranded core is generally more expensive than solid core.

Connectors need to be designed differently for solid core than for stranded. Use of a connector with the wrong cable type is likely to lead to unreliable cabling. Plugs designed for solid and stranded core are readily available, and some vendors even offer plugs designed for use with both types. The punch-down blocks on patch-panel and wall port jacks are designed for use with solid core cable.

The maximum specified distance for Cat5 cable is 100m. This allows for 10m of stranded cable at either end. Solid core has less attenuation than stranded cable, so a switch-to-switch link of solid cable, where the only connections are cable-plug-switch at either end can be significantly longer than 100m in practice. Experiments show that the practical limit is around 200m for 100 Mb/s. 1000Mb/s is intermittent at 200 m. These distances depend a little on the individual switches.

Low-end cable problem

The Communications Cable and Connectivity Association, Inc. (CCCA) in 2008 cautioned that many low-end communications cable products could present a significant fire risk. In response to concerns from the industry, the CCCA commissioned an independent laboratory to analyze whether nine randomly selected low end samples of these products met U.S. minimum requirements for performance and safety. Test results showed that none of the samples fully met all of the minimum requirements and eight of the nine samples failed to meet the National Fire Protection Association (NFPA) minimum code requirements for low flame spread and/or smoke safety requirements for installation in commercial buildings, schools and multi-tenant residences. Many of the samples failed the flame spread and smoke tests catastrophically. Because of the seriousness of these safety concerns, the CCCA plans to work in cooperation with the major leading independent telecommunications industry testing agencies to establish a new product certification program. Although details of the proposed program have not yet been established, a key component will be independent laboratory testing of structured cabling products that have been procured from point–of-sale locations.

Copper-clad aluminium

The American market had also been flooded with copper clad cable imported mostly from China and falsely presented in the market as being a 100% copper Cat 5e cable. With less copper involved in the manufacturing process, the cost to the consumer is lower, yet the consumer is not getting a true 100% copper Cat 5e cable.

Installation of copper clad aluminium Cat 5e wire has also been proven — by low-voltage contractors in the Southern California market, where this cable first arrived — to have poor test results and often not passing the Category 5e transmission standard. Since copper conducts electricity better than aluminium, signal strength has also been proven to be very weak over long runs using this substandard cable.

Additionally, some manufacturers have also falsely represented their Cat 5e cable conductors as being 24 American wire gauge. In actuality, a 26 AWG conductor is being sold and is hard to detect unless further examination beneath the sheath of the conductor is performed. A 26 AWG Cat 5e cable will not make proper contact on Cat 5e jack modules as most jack modules require 22 or 24 AWG per the specification and qualified connectors.

The United States Federal Government will not accept bids from China for Cat 5e cable due to China being absent from the Trade Agreements Act of 1979. In general, a product is only "TAA compliant" if it is made in the United States or a "Designated Country".

The Cat 5e “350 MHz” debacle

The 350 MHz term started a couple of years before the arrival of Category 6 cable by the Belden Electronics Division and promised better performance. Although the performance of this new 350 MHz cable was slightly better it was an easy way to sell the consumer on future proofing their needs while charging around 15% more and leading to a higher margin on the 350 MHz cable than the standard 5e cable. Soon after many other manufactures also offered a 350 MHz cable and followed the trend of an easy way to add to a higher margin. Some low-end cable manufacturers have the term “tested to 350 MHz” printed on the jacket as a way to appear to the consumer that they are receiving a better quality of 5e cable, but the cable was only “tested to 350 MHz” and no promise of a performance guarantee is ever mentioned.

As the 350 cable and term gained momentum, many manufacturers began offering a 400 MHz 5e cable, a 550 MHz 5e cable, and so on. This led to the consumer and communications contractor assuming and leaving them confused that the higher a MHz rating meant for a better performing cable. The arrival of the Category 6 cable standard which specified a delivered performance at 250 MHz left many people confused.

Connectors and other information

The cable exists in both stranded and solid conductor forms. The stranded form is more flexible and withstands more bending without breaking and is suited for reliable connections with insulation piercing connectors, but makes unreliable connections in insulation-displacement connectors. The solid form is less expensive and makes reliable connections into insulation displacement connectors, but makes unreliable connections in insulation piercing connectors. Taking these things into account, building wiring (for example, the wiring inside the wall that connects a wall socket to a central patch panel) is solid core, while patch cables (for example, the movable cable that plugs into the wall socket on one end and a computer on the other) are stranded. Outer insulation is typically Polyvinyl chloride or Low Smoke Zero Halogen, LSOH.

The cable is terminated in either the T568A scheme or the T568B scheme. Canada uses the T568A standard, and the United States commonly uses T568B scheme. It really doesn't make any difference which is used as long as you use only one of the standards so all connections are the same at your location to avoid confusion and potential problems. Mixed cable types should not be connected in series as the impedance per pair differs slightly and may cause signal degradation. The article Ethernet over twisted pair describes how the cable is used for Ethernet, including special Ethernet crossover cable.

Conductors required

10BASE-T (IEEE) and 100BASE-TX (IEEE) Ethernet connections require two cable pairs. 1000BASE-T (IEEE) and 1000BASE-TX (TIA/EIA-854, requiring category 6 cabling, unimplemented) Ethernet connections require four cable pairs. Four pair cable is by far most commonly available type.