What characterizes the category of twisted pair cable. Maximum UTP twisted pair length for LAN

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This guide discusses twisted pair cables designed to transmit digital information over Ethernet networks. There are many cables for other purposes that contain twisted pairs; the information in this guide may not be applicable to them.

In this guide, twisted pair means a communication cable containing two or four pairs of insulated conductors twisted together. Each pair is designed to transmit one signal: either transmitted data or received.

In this case, through one of the conductors of the pair, the signal is transmitted in antiphase to the other - this allows you to get rid of most electromagnetic interference: the receiver, having received two signals through a pair of wires, subtracts one signal from the other. In this case, the useful signal (since it goes in antiphase) is amplified, and the interference (moving along both wires in the same phase) is eliminated. Each pair of wires is marked with one color, with one of the wires of the pair marked with a solid color, and the second with the same color, but intermittently or with a stripe.

For the same purpose (protection from interference), pairs are twisted - this ensures the same impact of interference on both wires, regardless of the direction to its source.

Applicable twisted pair for laying analogue or digital telephone networks and for laying local computer networks, using mainly the Ethernet protocol.

Characteristics of twisted pair.

Category.
As a rule, the cable category is indicated by markings applied to the cable sheath at regular intervals.
Categories 1 , 2 , 4 V this moment practically never found, 4-pair category cable 3 occasionally used for laying telephone lines. Category 5 It differs extremely slightly from 5e, so it is almost impossible to find a Category 5 cable on sale. Since 2000, after the approval of category 5e, all manufacturers, without changing practically anything in the cable, began to mark it with 5e markings. This category remains the most popular to this day.

Category 5e implies a 4 or 2 pair cable that can be used in 10BASE-T Ethernet, 100BASE-TX Fast Ethernet networks (10 and 100 Mbit/s, respectively). The 4-pair cable can be used for laying 1000BASE-T Gigabit Ethernet networks (1000 Mbit/s). Maximum length cable without signal amplifiers is 100m.

Cable category 6 contains 4 pairs of conductors and can be used in 10GBASE-T 10 Gigabit Ethernet (10 Gbps) networks. When used in networks with speeds up to 1000 Mbit/s, the maximum cable length of this category is the same 100 m, when used in networks with speeds of 10 Gbit/s – 55 m.

Categories 6a, 7 And 7a imply shielded cables for networks with speeds up to 10 Gbit/s and a single line length of up to 100 m. The use of shielded cables imposes certain requirements both on equipment and on cable laying conditions (presence of high-quality grounding), which often makes laying a fiber optic cable more attractive . Reducing the cost of fiber-optic equipment and simplifying technologies for laying fiber-optic cables may in the near future make it completely pointless. further development twisted pair cables.

When choosing a cable category, you should keep in mind that it only speaks about the quality of the cable. The statement often found on the Internet that “category 5e cable operates at a frequency of 125 MHz, and category 6 cable operates at a frequency of 250 MHz” is incorrect. The cable operates at the frequency at which it operates network hardware. Replacing a category 5e cable with a category 6 cable in a 100BASE-TX network will not allow you to move to 1 Gbit/s without replacing network equipment (routers, switches, network cards). Moreover, if the old 5e cable was of high quality, replacing it with Cat 6 will not improve either the quality of the connection or its speed.

And vice versa, on short distances(up to 10 m) in 10GBASE-T networks you can use a high-quality 4-pair cable of category 5e - this will not affect the quality and speed of communication.

Number of pairs
Most cables contain 4 pairs wires But in 10BASE-T and 100BASE-TX networks only 2 pairs are used, so category 5e cable with two pairs conductors - it is lighter, thinner and cheaper than 4-pair. But for a network with a speed of 10 Gbit/s it is no longer suitable.

4-pair Category 5e cables are sometimes used for hidden installation. In this case, the “extra” two pairs remain in reserve and can be used in case of damage to the main pairs. In addition, there is network equipment that uses “free” pairs, for example, to transmit an audio signal or service information - in such networks a 4-pair category 5e cable can also be used.

For private LANs in an apartment or private house, it is recommended to install a hidden installation using a 4-pair category 6 cable, even if a network is supposed to be installed at a speed of 100 Mbit/s (quite sufficient today for most personal needs). This will provide a reserve for moving to more fast networks without re-cabling. And open sections and patch cords can be made from a cable that is most optimally suited to the current network. For networks with speeds up to 100 Mbit/s this will be a 2-pair cable of category 5e, for speeds of 1 Gbit/s - 4-pair 5e.

Twisted pair type most often speaks about the presence/absence of shielding and the type of screen.

The most common type is UTP(Unshielded Twisted Pair - “unshielded twisted pair”). As follows from the markings, there is no shielding on this cable. You can often hear the opinion that UTP cable is not protected from interference. This is wrong. UTP cables use balanced interference protection, which is quite effective in most cases.

FTP(Foiled Twisted Pair - “foil twisted pair”) has a common foil shield that protects the wires from powerful electromagnetic interference.

SFTP(Screened Foiled Twisted Pair) also has a mesh wire screen on top of the foil screen. The mesh screen enhances the cable shielding and protects the thin foil of the inner screen from damage.

At the same time, simply laying an FTP or SFTP cable instead of an unshielded one will not solve the problem of really serious interference - for efficient work cable, both ends must be grounded, as well as the network equipment used. In addition, grounding must be of high quality, which, for example, in an apartment building may not be feasible. A long, thin ground wire can act as an antenna itself, catching additional interference. And if the grounding bus (or PE wire in sockets) is not actually connected to the ground (which sometimes happens), then the screen grounded to this bus forms a closed circuit with it, providing excellent reception of all interference in the area.
Secondly, the screen forms a capacitance of a decent value, applied to the working wires and jamming (damping) the signal - the attenuation of the signal amplitude on the shielded wires is more pronounced.

Thirdly, cutting and crimping shielded wires is more difficult than for conventional unshielded cable. Violation of the contact between the screen and the cheeks of the connector for a shielded cable will disrupt the grounding of the screen and turn it into an antenna for catching interference.
Fourthly, damage to the screen leading to breakage of the contact (especially easy to occur on a foil cable due to excessive bending) will also reduce the cable's protection to zero.
Taking into account the above, in residential conditions the use of shielded cables seems unjustified.

As conductor material used either copper, or copper-plated aluminum, occasionally copper-plated steel. Copper plated aluminum provides worse conditions signal transmission than pure copper, but it is much cheaper. At the same time, when choosing a cable, information about the core material should be considered as additional to its category. The material of the cores can be decisive, for example when the line length is slightly longer than the standard. In this case, using copper cables is more likely to allow communication to be established. Under normal operating conditions, all cables of the same category should provide the same communication conditions, regardless of the core material.

The conductors in the cable can be stranded or single-core. This does not have much effect on the quality of communication, choose conductor capacity follows from the conditions of cable laying and its operation. Stranded conductors are more resistant to frequent bending, so such cables can be used to make patch cords for laptops or use them in lines that periodically have to be moved from place to place.

Not all Ethernet cables are created equal. What is the difference between them, and how to determine which cable category is needed? To understand this, let's look at the technical and physical differences between the categories of Ethernet cables.

Ethernet cables are grouped into sequentially numbered categories (cats) based on different specifications. Sometimes the concept of a category is clarified or supplemented by testing standards (for example, 5e, 6a). The category to which the cable belongs determines in what conditions it can be used. Manufacturers are required to adhere to standards, which makes choosing a cable and generally working with it easier for us.

Technical differences

Differences in cable specifications not only affect appearance cable; so let's take a look at the capabilities of each category. Below is a table of standards that can help you choose a cable for your case.

As the category number increases, the data transfer speed and frequency at which the cable operates also increases. And this is not a coincidence, because every new category places higher demands on crosstalk suppression (XT) and conductor insulation efficiency.

But these tables are not postulates at all. It is physically possible to use Cat-5 cable for gigabit speeds, and it is similarly possible to make the cable longer than 100 meters. The standard has not been tested in your specific conditions, so the results may vary. The opposite is also true; just because your cable is Cat-6, this does not mean that you will have a data transfer speed of 1 Gigabit/second. The network equipment and sockets to which this cable is connected must also support this speed, and there must also be appropriate settings in the network card driver, operating system and so on.

Category 5 has been revised and has been overwhelmingly replaced by Category 5 Enhanced (Cat-5e). Nothing has changed physically about the cable, just a stricter crosstalk standard has been applied.

Category 6 was revised to become Augmented Category 6 (Cat-6a), which tested at 500 MHz (compared to Cat-6's 250 MHz). More high frequency communication eliminated crosstalk (AXT), which made it possible to increase data transfer rates to 10 Gbit/s over long distances.

Physical differences

So, what physical cable parameters help eliminate interference and increase data transfer rates? It's all about insulation and the fact that the cable conductors are twisted in pairs. Conductor braiding was invented by Graham Bell in 1881, and it was he who first applied the technique to telephone wires running along power lines. He discovered that when twisting the cable every 3-4 posts, interference was significantly reduced and the signal transmission range increased. Twisted pair has become the basis for all Ethernet cables, reducing the impact of internal crosstalk and crosstalk from external sources.

The two main physical differences between Cat-5 and Cat-6 cables are the number of twisted pair turns per unit length and the thickness of the braid.

Twist lengths are not standardized, but typically Cat-5(e) has 1.5-2 turns per centimeter, while Cat-6 has more than 2 turns. Within the same cable, each color pair also has a different twist length based on prime numbers. The lengths of the turns are selected in such a way that two different turns never coincide. The number of turns per color pair is usually unique to each manufacturer. As you can see in the picture above, each color pair has a different number of turns per 1 inch.

Many Cat-6 cables contain nylon thread, which makes cable cutting easier and increases cable strength. Although filament is optional in Cat-5, some manufacturers add it anyway. In Cat-6 cable, the filament is also optional as long as the cable passes the standard's tests. In the picture above, only the Cat-5e cable contains nylon thread.

While the nylon filament increases the strength of the cable, the thicker braid protects against near interference and external crosstalk, the impact of which increases with frequency. In the picture, the Cat-5e cable has a thinner braid than the others, and only it has a nylon thread.

Shielded (STP) or unshielded (UTP) cable

Absolutely all Ethernet cables are twisted, but manufacturers have gone further and use shielding to combat interference. Unshielded twisted pair cable is fine for laying a cable from a wall to a computer, but when laying in areas with high noise levels, outdoors or inside walls, it is highly advisable to use a shielded cable.

There are several ways to shield an Ethernet cable, but the usual way is to make a shield of foil around each pair. This protects against mutual interference between pairs within the cable. Some manufacturers additionally protect conductors from external crosstalk by adding UTP or STP cables external screen. So, the picture at the top right shows a Screened STP cable (S/STP).

Solid or twisted cable

The term solid or stranded cable refers to the actual copper conductors within the cable. Solid means that the inner conductor is a single piece of copper, while stranded means that the inner conductor is made of several thin copper conductors twisted together. For each type of conductor different applications, but most readers only need to know about two of them.

Stranded cables (Stranded, pictured above) are more flexible and should be used where the cable will move frequently, such as near work areas.

A solid cable (Solid, in the picture below) is not as flexible, but is more durable, it can be ideally used for permanent networks– both outdoors and indoors.

This is a translation of the article

It is becoming more and more difficult to understand the accelerating modern flow of goods and technologies provided. First of all, this concerns computer equipment and accessories for it. The latter also includes various types of information cables, the names of the markings of which are easy to get confused even for a specialist. In the article below, a study will be conducted, the purpose of which is to identify the main distinctive properties of UTP, FTP, STP and other twisted pairs.

The meaning of information cable markings

On modern market Structured cabling systems (SCS) include many twisted pair names that are obscure to buyers: UTP, S/UTP, F/UTP, FTP, ScTP, STP, S/STP... The list goes on. And in order not to get confused in the multitude of labels when choosing the necessary product, you should find out the meaning of English abbreviations.

Looking closely at the designations of twisted pairs, it is easy to notice that the last two capital letters TP is found in almost all types of cables. This is an abbreviation for Twisted Pair. Translated from in English it means “twisted pair”. The letter U before Twisted Pair stands for the shortened passive participle Unshielded. It is translated as “unprotected”. Therefore, any cable with the abbreviation UTP is considered an unprotected twisted pair cable. To put it more clearly, between our twisted pairs does not have individual layers of insulation.
LAN cables, inside which the copper pairs are insulated from each other, are called Shielded Twisted Pair (STP). The group of STP cables includes the marking of twisted pair PiMF (Pairs In Metal Foil). Translated, this phrase means “a pair in metal foil.” LAN cables S/STP, F/STP should also be classified as this type. The letter S before the slash means Shielded, and the F (Foiled) means obstructive, but in this context it translates as “foiled.” However, it cannot be argued that the concepts S/STP and F/STP are almost synonymous. The differences between the two are that the outer shield of the F/STP is made of aluminum foil, while the overall shield of the S/STP is made of braided copper wire. It should be noted that, classified in North America (Canada and the USA) as ScTP (Screened, shielded), also refers to protected types of LAN cables that have a common aluminum shield.

International classification of information cables

However, there is confusion among manufacturers regarding LAN cable encodings. And the problem arises when it is necessary to clarify the location of the shielding layer. The latter can be located in two places. The one on top of a separate pair is called individual. Located around pairs isolated from each other ( twisted pair ftp) is usually called general. To avoid confusion, an international classification of LAN cables was created. When compiling it, the following were taken into account:

presence of a shared screen;
a layer of insulation over a separate pair of conductors;
twisting method.

The classification scheme for information cables was presented in the form of the AA/BCC formula. The first 2 letters on the left indicate the presence of a common shield over all twisted conductors. For example, an S/FTP cable differs from an FTP cable in that all double conductors have a common shield made of copper braid.
The third letter (B) carries information about the existence of an individual shield around each twisted pair of conductors. If there is one, then this is the one twisted pair ftp. The last two letters indicate the type of twist. Usually this is tp. However, in Lately The abbreviations “TQ” are becoming increasingly common. They mean that the conductors are twisted not in pairs, but in fours. Returning from “quads” to twisted pairs, the most tricky question should be clarified. If there is no shield around each individual twisted pair, and the protection is located only on top of all double conductors, then each of them is referred to as twisted pair utp, and the cable marking will look like this: F/UTP or S/UTP.

Features of the STP cable name

There is a lot of confusion when choosing the required cable, which is designated STP. This marking may refer to a different cable.

For example, shielded twisted pair cable (S/FTP, F/FTP, SF/FTP, or S/STP) is also called STP. In addition, the name STP indicates the material from which the cable screen is made - braid.

STP cable is widely used for data transmission using 10 GbE technology over twisted copper pairs.

UTP and FTP cables: main differences

Having understood a little about the international classification of twisted pair cables, you should consider the distinctive characteristics of UTP and FTP twisted pairs. In terms of information utp 4 cable, which has neither individual screens for twisted pairs nor a common screen, has one more difference. It does not have a drain wire, which is usually found in shielded LAN cables. For example, ftp cable 5e, the price of which is lower than the competitive one is equipped with this element. The drainage wire has no insulation and is connected along its entire length to a common aluminum screen. It is provided in case of sudden rupture of the aluminum sheath due to strong bends or excessive stretching of the cable. In this situation, the drainage wire becomes a kind of connecting clamp for the screen.
Aluminum or aluminum-polymer film is used for shielding in FTP cables. The latter is laid with the metal side inward, on the surface of pairs of twisted conductors. As a result
additions additional elements foil coaxial cable(FTP) becomes slightly thicker than unshielded twisted pair (UTP). In addition, FTP is somewhat less flexible than UTP.
Foil twisted pair cable has an advantage over unprotected twisted pair cable. The first is better protected from high-frequency interference. But for this purpose it’s vaporous ftp cable and the case of a computer or other electronic equipment must be grounded according to all rules. The situation with interference on low frequencies. Aluminum screens are not able to prevent low-frequency waves generated by powerful brushed motors. For this reason, FTP twisted pair cables are not used in industrial production. In addition, foil LAN cables are characterized by low signal attenuation parameters.
When comparing the disadvantages and advantages of protected and unprotected twisted pairs, you should not forget about the price. For a low budget cable utp buy much more profitable, since its cost is much lower than a foil LAN cable.
Statistics show that ftp cable more often used in France. And a significant part of the computer networks in the United States and England is equipped based on UTP cables. Residents of Germany prefer twisted-pair cables with two shields: individual for each pair of conductors and a common one. You can buy twisted pair cables from AVS Electronics.

The meaning of some English abbreviations on LAN cables

When choosing an information cable for your needs, you need to carefully read the labels on it. Knowing symbols abbreviations, any buyer can easily select the appropriate product. The letter combination LAN itself is translated as “local computer network”. And this term does not carry the technical characteristics of the product.

It is much more important to pay attention to the abbreviation CCA, which informs the buyer that this is a cable in which the conductors are made of aluminum and clad (covered on top) with a layer of copper. In Russian, the term “composite” is used instead of CCA. The latter indicates that cable - twisted pair ftp or utp - does not consist of copper conductors, but of aluminum clad with copper. The cost of these is several times less, however, they are also specifications much lower.
For example, twisted pair, the most common version of twisted pair.
Concluding the study, it should be noted that all information cables of the Cat5, Cat4 and Cat6 categories are equipped with 4 twisted pairs inside. The letter E after Cat5 indicates that the category is extended. And for the manufacture of FTP twisted pairs of the Cat5e class, it is mandatory to use not aluminum, but copper wires. You can buy UTP twisted pair cable from AVS Electronics. The company also has various varieties in its assortment.

The definition of a twisted pair cable category is based on the maximum transmittable frequency range. This is due to the number of turns per unit length of cable. That is, the higher the category, the greater the transmitted frequency range due to the increase in the turns of each twisted pair. Categories of twisted pair cables are described in international and domestic standards.

The categories (abbreviated CAT) of twisted pair cables determine the design data transfer rate. Besides LAN cable They are also divided into classes and they are also taken into account when building a structured cabling system. Please remember that higher grade twisted pair cables support technical capabilities lower class. But twisted pair cables of a lower class do not support technical applications upper class. The higher the class, the better the transmission characteristics and the higher the maximum operating frequency of the cable line.

CAT1(frequency band - 0.1 MHz). It has one pair and is used to transmit voice and digital data using a modem. This is a standard telephone cable, which at one time was used in a “twisted” form in the USA, and in Russia it is still used without twists. Not suitable for modern systems and has a large interference effect.

CAT2(frequency band - 1 MHz). It has two pairs of conductors and has already become obsolete. Sometimes used when building telephone networks. Previously seen in the Arcnet and Token Ring networks. Has data transfer speeds up to 4 Mbit/s. Not suitable for building modern networks.

CAT3 (frequency band - 16 MHz. Class "C"). There are 2-pair and 4-pair types of twisted pair. It is used not only to create telephone networks, but also local networks based on 10BASE-T. Supports data transfer rates from 10 to 100 Mbit/s using 100BASE-T4 technology over a length of no more than 100 meters. Unlike CAT1 and CAT2, it supports the IEEE 802.3 standard.

CAT4(frequency band - 20 MHz). At one time, this 4-pair cable was used in 10BASE-T and 100BASE-T4 technology. Data transfer rates up to 16 Mbit/s are possible. Not used these days.

CAT5 (frequency band - 100 MHz. Class "D"). The cable was used to create telephone lines and build 100BASE-TX local networks, as well as Ethernet (LAN). Supports data transfer rates up to 100 Mbps.

CAT5e(frequency band 125 MHz). This is an advanced category 5 twisted pair cable. When using 2 pairs, it supports data transfer rates of up to 100 Mbit/s and up to 1000 Mbit/s in a 4-pair cable. As a rule, a 4-pair cable is used to build a local computer network. This is the most common type of twisted pair cable.

CAT6 (frequency band 250 MHz. Class "E"). This is a common type of cable that is used in Fast networks Ethernet and Gigabit Ethernet. The cable structure has four pairs of conductors. Supports high speed data transmission up to 10 Gbit/s over a length of no more than 55 meters.

CAT6a(frequency band 500 MHz. Class "E A"). The cable structure consists of four pairs of conductors. It is used in Gigabit networks Ethernet and supports speeds up to 10 Gbps over a distance of up to 100 meters.

CAT7(frequency band 600 - 700 MHz. Class "F"). Supports data transfer rates up to 10 Gbps. The cable structure has a common outer shield and foil protection for each pair. The type is S/FTP (ScreenedFullyShieldedTwistedPair).

CAT7a(frequency band 1000 -1200 MHz. Class "F A"). Twisted pair speeds reach up to 40 Gbit/s over a distance of up to 50 meters and up to 100 Gbit/s over a distance of up to 15 meters.


trunk cable, design features
Twisted pair cables, which have three or more four-pair elements under a common sheath, are classified as multi-pair cables. The main cable is intended for use in the backbone subsystems of SCS for connecting cross-connection rooms between each other. In the subsystem of external highways, usually most of the route is laid horizontally, in the subsystem of internal highways - vertically. In order to reduce the attenuation coefficient, conductors are made of monolithic copper wire. Unlike horizontal cable, trunk structures contain more than four twisted pairs and are therefore often called multi-pair. Similar to horizontal cables, they vary in categories from 3 to 5, with trunk cables of category 4 being very rare in practice. The design of the cable depends on its capacitance. When the number of pairs is up to 25, they are placed in a common shell. In the case of a capacity of more than 25 pairs, they are divided into bundles of 25 pairs each, the totality of which forms the cable core.

Fig.4 Multi-pair trunk cables: a) 25-pair cable of category 5 b) 300-pair cable of category 3
Some designs use a central fiberglass core as the core. The wires of one bundle are fastened with polyethylene tapes. From the outside, the core is protected by a common dielectric shell. In addition to unshielded trunk cables in limited quantities S/UTP structures are produced, in which under the outer dielectric shell there is a screen covering the cable core. Similar to horizontal cables, markings are applied to their sheath, including the type, data on the diameter of the conductors and their number, the name of the testing laboratory, as well as foot or meter length marks. The linear weight of a 25-pair category 5 cable is usually ISO-190 kg/km, the operating temperature range is from -20 to +60°C. In addition to multi-pair cables, a number of companies offer so-called Multi Unit cables. They differ in that the cable core is formed not by individual twisted pairs, but by two- or four-pair elements, similar in design to a horizontal cable and equipped with an individual protective sheath. To increase strength and resistance to various mechanical influences, a central fiberglass rod can be used as the basis for the core of a multi-element cable. Trunk cables are divided into internal and external cables. The main difference between an external cable and an internal cable is the use of special measures and design solutions to protect the cable core from moisture ingress. This problem is most often solved by using an outer polyethylene sheath. Some types of telephone cables have helium filling the internal voids of the core. Additional protection of the cable core from moisture and mechanical influences made with armor made of aluminum or steel corrugated tape.

Crimping twisted pair

Crimping a twisted pair cable is most often done with an 8P8C connector, more commonly called RJ-45 (RJ45) according to color scheme corresponding to the purpose of the cable.

RJ-45 connector (left - for twisted pair FTP/STP/SSTP, with shielded housing, right - UTP)

RJ-45 connector for twisted pair FTP STP SSTP and RJ-45 connector for UTP:

There are two main cable crimping schemes: T568A and T568B, but T568B is much more commonly used. To connect a computer to a switch or a computer to a hub, use a straight cable, crimped on both sides equally; computer-to-computer or switch-to-switch (hub-to-hub) connections use crossover cable(crossover, сrossover) - on one side T568A, and on the other - T568B.

Crimping diagram for 4-pair cable:

Crimping diagram for a 2-pair cable (the color of the pairs may vary depending on the cable manufacturer):

If you connect computers directly to each other via Gigabit network cards, use the Gigabit Crossover scheme:

Gigabit Crossover:

If you decide to use FTP/STP and ground the shield - ground only in one place and only 100% grounded! If in doubt, it’s better not to do it at all; “grounding” it to a heating radiator or electrical panel housing can only make matters worse - not only for the computer, but also for you!

Since our site is about Wi-Fi routers, and other network equipment, then I just had to prepare an article about twisted pair - the cable that connects network equipment to each other. With the help of which computers and other devices are connected to routers and modems. Also, with a cable called twisted pair, most likely you have an Internet connection from the provider’s equipment to your router, or directly to your computer. Also, almost all router manufacturers include a short network cable with their devices. It is needed to connect to the router different devices (PC, laptop, TV, game console etc.).

IN modern world The development of data transmission technologies is occurring at a truly rapid pace. It is quite possible to say “at the speed of light”, because no one will be surprised by the transmission of information flows using optical fiber. But with all the positive functional characteristics Such communication cables have several serious disadvantages. The key ones are high cost and fragility.

At the moment, you have to try very hard to find a person who has absolutely no idea what the Internet is or has never used it. U huge amount people are at home Personal Computer with access to " world wide web" But in order to “connect” the Internet to your home PC, you need to use a convenient, reliable, and most importantly strong cable. This is where a cable has come to the rescue for many years, given an incomprehensible, at first glance, name - twisted pair.

What is twisted pair?

Twisted pair is a special type network cable. It is based on one or more pairs of insulated and twisted conductors. (the cable category depends on their number). The number of turns per specific unit of length is minimal, but sufficient to significantly reduce mutual guidance during signal transmission. The top of the twisted pair is usually covered with a protective plastic sheath.

Recently, this type of communication cable has become the most common when creating local and structured cable networks. This happened due to its low cost and ease of installation.

The main disadvantage of twisted pair cables is significant signal attenuation (to the level of unrecognizability) at distances over 100 meters. But this drawback is easily eliminated with the help of repeaters.

Kinds

Depending on whether there is protection or not, as well as its quality, there are several types of cables created using this technology:

unshielded twisted pair (UTP) – no additional protective devices are used;
shielded twisted pair (STP) – copper mesh is used;
foil twisted pair (FTP) - aluminum foil is used;
shielded foil twisted pair (SFTP) - uses copper mesh and aluminum foil.

However, some types of shielded cable may use protection around each pair. This type of shielding provides significantly better protection from various kinds of guidance, both internal and external.

Twisted pair cable categories

In total, there are currently about 15 categories of twisted pair cables. They are numbered from CAT 1 to CAT 8.2. In most cases, the category has a direct dependence on the number of pairs used to transmit information, as well as on the number of turns that are used per unit length. Cable categories are clearly described in the American Commercial Wiring Standard.

Let's briefly describe each of the categories:

CAT 1 is a well-known telephone cable. It only uses one pair. Applicable exclusively for voice transmission and creating connections using a modem.
CAT 2 is an outdated type of cable, consisting of 2 pairs of conductors. It supported data transfer at speeds less than 4 Mbit/s. Often used in networks token ring. Now rarely used in some telephone networks.
CAT 3 is an improved version of the previous 2-pair cable. Designed to provide data transmission at speeds up to 10 Mbit/s. Now it continues to be found very often in telephone networks.
CAT 4 is another type of cable that is not used today. Consists of 4 pairs, has a transmission speed of up to 16 Mbit/sec.
CAT 5 – it is the cables of this category that are most often called “twisted pair” in its classical sense. Consists of 4 pairs. The transfer speed varies from 100 Mbit/s (2 pairs are used) to 1000 Mbit/s (4 pairs are used).
CAT 5e is an improved version of the usual 5th category. Also consists of 4 pairs. The cable has the same speed characteristics as the twisted pair cable of the previous category. Now this category is the most common.
SAT 6 – 4 pairs are used for transmission, which allows you to increase the transmission speed to 10,000 Mbit/s.
SAT 6a - 4 pairs are used for transmission, which allows you to increase the transmission speed to 10 Gbit/sec.
SAT 7 - 4 pairs are used for transmission, which allows you to increase the transmission speed to 10 Gbit/sec. The cable of this category must be shielded.
CAT 8 is currently in development. Presumably will allow you to transmit information flow with speeds up to 40 Gbit/sec. Must have a shared screen or a screen for each couple.

Methods and schemes for crimping twisted pair cables

Obviously, to connect the cable to various computer technology or to switches and routers, the twisted pair cable must be terminated with convenient and standardized connectors. This type of communication cable uses an RJ-45 connector (correct name 8Р8С, but we will use the usual one).

In order for a network built on twisted pair to work correctly, it is necessary to connect the contacts in the RJ-45 connectors in the appropriate order. This must be done from both one and the other end of the cable. For ease of crimping, all wires are marked with standardized colors. Naturally, if you have sufficient knowledge, you can crimp the cable at your own discretion, but in order to avoid confusion when connecting networks, it is better to use standard schemes crimping There are only two of them: direct crimping order and cross crimping order (crossed).

The first crimping scheme (direct) is used when connecting different types of equipment, for example, LAN card laptop and switch.
The second crimping scheme (crossover, or cross) is used when connecting equipment of the same type, for example, two laptops (sometimes to connect a computer to some older types of switches and hubs).

To crimp the cable, use a special device - a crimper (pliers). I wrote about this in the article: .

And now directly about the crimping procedure. Let's consider crimping circuits for twisted pair cables of category 5, as the most common at the moment.

Straight Cable Crimping Diagram

This cable is the most common. It is suitable for connecting computers, laptops, TVs, etc., to routers and other network devices.

First option (type T586A): one side has the following order of contacts (from 1 to 8) - white-green, green, white-orange, blue, white-blue, orange, white-brown, brown. The other side has the same contact order. It is best to use this option.
Second option (type T568B). One side has the following order of contacts (from 1 to 8) - white-orange, orange, white-green, blue, white-blue, green, white-brown, brown. The other side has the same contact order.

Crossover cable: crimp diagram

One side has the following order of contacts (from 1 to 8) - white-green, green, white-orange, blue, white-blue, orange, white-brown, brown.
The other side has the following pin order (from 1 to 8) - white-orange, orange, white-green, blue, white-blue, green, white-brown, brown.

For making Gigabit crossover cable (supports speeds up to 1 Gbps), you need to use a slightly different scheme:

One end of the cable: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown.
Other end of the cable: white-green, green, white-orange, white-brown, brown, orange, blue, white-blue.

The development of data transmission technologies does not stand still. It is theoretically possible that twisted pair cable will soon become an obsolete type of cable, but at the moment it is the most used, reliable and cheapest type of network cable.