utp categories. Twisted Pair - PIE.Wiki. Rarely used perspective categories

To create communication networks, computer and communication, cables are used, made according to special technology. Their veins are twisted in pairs with each other. Such products are called "twisted pair". There are two main types of cables of this design: ftp and utp.

UTP (top) and shielded FTP (bottom)

Twisted Pair Features

The main problem in the protection of communication lines is their protection from interference. The signal amplitudes in the line are much smaller than those of the surrounding electrical equipment: in power cable lines, electric motors, household appliances, overhead power lines. Taking into account the degree of development of electrification, it is not difficult to imagine the number of electromagnetic pickups affecting communication cables along their entire route.

Upon completion of this chapter, you will be able to.

Describe the main types and uses of twisted pair cables.
Describe the main types and uses of coaxial cables.
Describe the main types and uses of fiber optic cables.
Describe the main types and uses of wireless media.
Compare and contrast the main types and uses of different media.

Network media is the actual path that an electrical signal takes as it passes from one component to another. This chapter describes common types network media, including twisted pair cable, coaxial cable, fiber optic cable, and wireless communication.

In addition, the cores inside the cable itself act on each other, creating mutual interference. When communication lines were carried out using the same technology as electrical ones (in the form overhead lines with wires on insulators), interference from adjacent conductors and high-voltage power lines was minimized by regularly changing the location of the line conductors relative to each other. This technical trick called a transposition.

A pair of wires forms a circuit that can transmit data. These pairs are twisted to provide protection against crosstalk, noise generated by adjacent pairs. When electricity flows through the wire, it creates a small circular magnetic field around the wire. When two wires in an electrical circuit are close to each other, their magnetic fields are exactly opposite to each other. So two magnetic fields cancel each other. They also compensate for any external magnetic fields.

What is twisted pair for?

Twisting wires can increase the cancellation effect. By using cancellation along with wire twisting, cable designers can effectively provide self-protection for pairs of wires in a network carrier. There are two main types of twisted pair cable: unshielded twisted pair and shielded twisted pair.

Transposition on the example of a power line

The twisted pair in modern cable is the same transposition, but done with high density. The veins are twisted together in pairs. This achieves the minimum influence of individual pairs of wires on each other and increases the protection from external interference.

In addition, the wires in each pair are twisted around each other. It can be extremely an important factor to consider, especially when installing a network in an older building. However, disadvantages are also associated with the use of twisted-pair cables. Category 1 Used for telephone communications. . Shielded twisted pair cable integrates shielding, canceling and wire twisting technologies. Each pair of wires is wrapped in metal foil. The four pairs of wires are then wrapped in a common metal braid or foil, usually a 150 ohm cable.

However, the protective properties of twisted-pair cables are reduced to nothing if the conditions for their laying are violated. The bending radius of such products is strictly limited and usually should not be less than eight diameters. If this is not taken into account, then geometric changes occur inside the cable, sometimes irreparable, worsening its noise immunity.

Twisted Pair Types

In addition, metal shielding must be earthed at both ends. If it is not properly grounded, the shield acts as an antenna and picks up unwanted signals. The speed of both types of cables is usually satisfactory for local distances. These are the least expensive means of data transmission. . Like a shield used during battle, shielding in cables acts as a barrier to protect the cable from external threats such as electrical interference. It also prevents cables from interfering with surrounding cables and equipment.

The twisted pair bending radius must be at least 8 cable diameters

Shielding of communication cables

However, twisting the cores does not always help to completely eliminate the effect of interference on the useful signal. In this case, the introduction of shielding shells into the design helps. Shielding can be applied to both individual pairs of cores and all cores inside the cable. These methods are applied both separately and together, in this case each pair of cores is shielded and, additionally, all cores together.

While not all environments require such a reliable cable, shielding is becoming more and more common. When it first appeared, shielded cables were used in areas such as factory floors, areas with a high concentration of electrical equipment, and secure communications applications. Today, shielded cable is widely used in many types of applications, including government, healthcare, and even education.

The "shield" under the jacket is a braid, and each individual pair is surrounded by its own foil barrier. Now that you've read these shielded cable types, you can refer to this handy guide to keep them straight. Our global facilities produce a variety of shielded cable styles and our experts can help you find the one you need. However, some terms must be defined before any meaningful comparison can be made.

However, this method of protection is effective only if the equipment cases connected by a cable are grounded. Otherwise, the screen shells themselves become a source of interference, accumulating them along the entire path of the line.

Depending on the presence, absence and number of screens, a letter is added to the cable brand, meaning:

Imagine that you can only drive two cars, one passenger at a time, on a highway in each of two lanes. Now you can transfer more people on the same highway if you can drive the same two cars for 500 trips a day compared to 250 trips a day. Now imagine the same analogy, but replace cars with bits of data. So if you can only drive two bits on a given data line, then 100 MHz will give you more bandwidth than 50 MHz.

Like many other cable options, it relies on copper for data and power transmission. In addition, pairs of wires are twisted more tightly and protected from heavy-duty shielding to eliminate crosstalk. Crosstalk reduces the speed at which a cable can transmit information. In other words, he can handle throughput up to 1Gbps at distances up to 100 meters.

U - no screen;
S - common screen in the form of a metal braid;
F - screen made of copper or aluminum foil or metallized tape around the strands of each pair or all as a whole.

The full designation of the brand consists of the above letters written through a fraction. The numerator indicates the protection of individual cores, the denominator indicates the protection of the entire cable. Next, the letters "TP" are added, denoting "twisted pair", in translation - twisted pair.

Definition

Finally, one thing to always remember is that any custom cable can be built to suit the application in any project. A twisted pair cable is a type of cable that is connected by two separate insulated wires twisted and running parallel to each other. This type of cable is widely used in various types data and voice infrastructure.

Experts point out that twisted-pair cables are often used to prevent certain types of interference. Two types of twisted pair, unshielded twisted pair and shielded twisted pair, are used in various types of installations. In general, twisted-pair cables may be preferred over the common alternative, coaxial cable, over different reasons. Coaxial cable includes one, thicker wire. Many people who use this type of cable claim that twisted pair has a more acceptable bend radius, is easier to terminate, and provides more versatility when choosing network topologies.

For example, the designation U/FTP means that the cable does not have a protective shield of individual pairs of cores, but contains a common shield. There are also combinations of their two letters, for example "SF" - a metal braid and foil are used together.

Standard network cable, defined by the Electronic Industries Association and the Telecommunications Industry Association. The key component in wired home networks are the wires! What is the difference between wire and cable? A wire is a single conductor that can be solid or stranded. two or more insulated wire, grouped together in a sleeve or jacket, form a cable.

Categories of twisted pair cables

Two wires are twisted together into a pair for a total of four pairs, and then four pairs are twisted together to form a cable. Twists and pairs affect certain cable performance characteristics such as crosstalk, attenuation, and EMI.

Unshielded shielded cables

Unshielded twisted-pair cables are used in both large corporate networks and small home networks.

It should be borne in mind that when using foil for shielding, its outer surface is covered with a dielectric layer. Therefore, when connecting the screen, you need to use only it inner surface for contact connection.

If the screen is made of foil, then a metal wire of small cross section runs parallel to it. It is necessary for better contact when connected to grounding devices. It also eliminates possible breaks in the foil screen that occur in places of kinks, as if shunting the places of breaks.

Straight and crossover cables

It is relatively inexpensive and much more flexible than shielded twisted pair cables. It is used in industrial environments and other noisy environments that are subject to high electromagnetic interference. Crossover cables are sometimes required to directly connect two computers together, to connect very cheap network switches that don't have an uplink port, or to connect some types of specialized networking devices. The difference between straight and crossover cable is subtle but important.

Which cable is better: with or without a shield?

Which one is better to use cable when laying communication networks, utp or ftp? It would seem that the use of shielded cables solves all problems with noise immunity, and unshielded cables only partially cope with the task.

Length and color of network cables

When choosing cables for your network, you also need to consider length and color. Longer lengths are available and you can also create your own cable length. The distance between the various network devices and the network switch or router will determine the required length. Be sure to include enough length to run cables along walls, under rugs, and around corners as needed. This decision may be based solely on your individual preferences and preferences. Blue is perhaps the most common, but you can also consider white, gray, or some other color that doesn't clash with your walls and carpets. Finally, you can use the same color for all cables on your network. detailed information about all category communication cables.

It wasn't there. Recall the ability of the screen to accumulate interference in the absence of grounding. If the equipment to which it is connected does not have a connection to the ground loop (or its own ground loop, which is mandatory for servers), then using ftp will only make the situation worse.

In addition, ftp cables are very sensitive to low-frequency interference, the level of which is manufacturing enterprises quite high due to the presence of power electrical equipment. No matter how hard you try, the laying of communication cables is still impossible at a sufficient distance from existing power lines. And the cable products passing through them always radiate pickups around them. In addition, interference is emitted by electric motors and induction elements. Do not forget about the impulse noise that occurs during the operation of switching devices.

The shield also reduces radiation at any point along the way. However, both types of cables have some immunity to interference due to the twisted-pair design of the conductors. Shielding also makes the cable heavier and more rigid. So it's more difficult. The twisted pair is twisted together to eliminate electromagnetic interference from external sources; for example, electromagnetic radiation from unshielded twisted-pair cables and crosstalk between adjacent pairs. The advantage of twisting is that all wires are equally affected by external influences, so unwanted signals are cancelled.

Another utp cable, unlike ftp, has a lower attenuation value of the useful signal. That greatly affects the long length of the communication line.

Therefore, when deciding which cable to choose, unshielded or ftp, you need to focus on whether the equipment has the ability to connect a shield, the presence or absence of low-frequency interference, and overall length communication lines.

What are twisted pairs

The role of twisting is to minimize interference from external magnetic fields. Category 5 cable is a multi-pair, high-performance cable consisting of twisted-pair conductors used primarily for data transmission. The unshielded twisted pair design makes the cable very economical for data networks.

In the new standard, performance requirements have increased slightly. The quality of the data transfer depends on the performance of the link components. When looking at cables, one should ask oneself about the need to eliminate electromagnetic interference. This means that shielded or unshielded cable comes into play.

Even when choosing a cable, you need to pay attention to the material of its sheath. If it passes through open areas on the street, then it must be protected from exposure sun rays. To do this, the outer shell is made of polyethylene, usually it is black. But the polyethylene sheath that protects the cable from sunlight, temperature fluctuations and precipitation supports combustion. Therefore, indoors they can not be laid openly.

The meaning of some English abbreviations on LAN cables

First, let's look at what electromagnetic interference or radio frequency interference is, how it can be caused. This perturbation is generated by an external source acting on electrical circuit electrostatic coupling, electromagnetic induction or conduction. This type of noise can reduce the performance of the circuit or stop it from working. Where there is a data path, these types of effects range from increased error rates to complete loss of data. Natural as well as artificial sources generate change electric currents and voltages that can cause electromagnetic interference.

For indoor use, the enclosure must be non-flammable and must not emit halogens (fluorine, chlorine, bromine or iodine). They are not only strong oxidizing agents, but also poisonous to humans. Flame-retardant sheaths are indicated by adding the letters LS (low smoke) to the cable marking for imported products or “ng” for Russian products. Not emitting halogens are additionally labeled HF (halogen free).

twisted pair It is used as a transmission medium in all modern network technologies, as well as in analog and digital telephony. The unification of passive elements of a twisted pair network has become the basis for the concept of building structured cabling systems that are independent of applications (network technologies). All twisted-pair networks (except the legacy LocalTalk) are based on a star-shaped physical topology, which, with the right active equipment, can serve as the basis for any logical topology.

Twisted pair or twisted pair cables (Twisted Pair cable or TP), unlike coaxial cable, are symmetrical and are used for differential (balanced) signal transmission. A twisted pair of wires differs significantly in properties from a pair of the same straight wires running side by side parallel to each other. When twisting, it turns out that the conductors always go at a certain angle to each other, which reduces the capacitive and inductive coupling between them. In addition, a significant segment of such a cable for external fields turns out to be symmetrical (round), which reduces its sensitivity to interference and external radiation during signal transmission. The smaller the twist pitch, the less crosstalk, but also the greater the per unit attenuation of the cable, as well as the signal propagation time. The cable may have different designs, individual pairs may have a screen made of copper wire and/or foil. All cable pairs can also be enclosed in a common screen. For the first time in network technologies, twisted pair was used in Token Ring networks - the so-called IBM STP Type 1 cable. It was (and is) an expensive and bulky cable that requires rather large connectors. Currently, twisted pair cables are constantly being improved, mainly in the direction of expanding the bandwidth. 100 MHz is already a common value for cable bandwidth, standards are being developed for cables with a bandwidth of up to 600 MHz.

A twisted pair wire consists of two twisted insulated conductors. Such a wire is used for cross-wires inside wiring closets or racks, but not for laying connections between rooms. The crossover wire can consist of one, two, three or even four twisted pairs. The cable differs from the wire by the presence of an external insulating stocking (jacket). This stocking mainly protects the wires (cable elements) from mechanical stress and moisture. The most widely used cables contain two or four twisted pairs. There are cables for big number couples - 25 couples and more. Cord (cord) is a piece of flexible (stranded) cable of relatively short length. A typical example is a patch cord (patch cord) - a piece of stranded 4-pair. cable length 1-5 m with modular 8-pin plugs (RJ-45) at the ends.

Twisted Pair Categories

Category (Category) twisted pair determines the frequency range in which its use is effective (ACR has positive value). There are currently standard definitions for 7 cable categories (CAT1...CAT7). The categories are defined by the EIA/TIA 568A standard.

CAT1- (bandwidth 0.1 MHz) telephone cable, just one pair, known in Russia as "noodles". In the USA it was used earlier, and the conductors were twisted together. Used only for voice or data transmission using a modem.
CAT2- (frequency band 1 MHz) old type of cable, 2 pairs of conductors, supported data transfer at speeds up to 4 Mbps, used in Token Ring and ARCnet networks. Now sometimes found in telephone networks.
CAT3- (bandwidth 16 MHz) 2-pair cable, used in the construction local networks 10BASE-T and Token Ring only supports data rates up to 10 Mbps. Unlike the previous two, it meets the requirements of the IEEE 802.3 standard. Also still found in telephone networks.
CAT4- (frequency band 20 MHz) cable consists of 4 twisted pairs, used in token ring, 10BASE-T, 10BASE-T4 networks, data transfer rate does not exceed 16 Mbps, is not used now.
CAT5- (bandwidth 100 MHz) 4-pair cable, this is what is commonly called a "twisted pair" cable, thanks to high speed transmission, up to 100 Mbps when using 2 pairs and up to 1000 Mbps when using 4 pairs, is the most common network carrier used in computer networks still. When laying new networks, a slightly improved CAT5e cable (125 MHz frequency band) is used, which better transmits high-frequency signals.
CAT6- (frequency band 250 MHz) is used in Fast Ethernet and Gigabit Ethernet networks, consists of 4 pairs of conductors and is capable of transmitting data at speeds up to 10000 Mbps. Added to the standard in June 2002. There is a category CAT6a, in which the frequency of the transmitted signal is increased to 500 MHz.
CAT7- data transfer rate 10000 Mbps, signal transmission frequency up to 600-700 MHz. This category of cable is shielded. Thanks to the double shield, the cable length can exceed 100 m.

Types of cable twisted pair

In addition to the generally accepted designations of cables by category, there is also a classification of cables by type (Type), introduced by IBM.

Twisted pair can be either shielded (shielded) or unshielded (unshielded). The terminology of screen designs is ambiguous, the words braid (braid), shield and screen (screen, protection), foil (foil), tinned drain wire (tinned “drain” wire running along the foil and slightly wrapping around it) are used here.

Unshielded twisted pair(NVP) is better known by its acronym UTP(Unshielded Twisted Pair). If the cable is enclosed in a common shield, but the pairs do not have individual shields, but, according to the standard (ISO 11801), it also belongs to unshielded twisted pairs and is designated UTP or S / UTP. This also includes STP (Screened Twisted Pair) or FTP (Foiled Twisted Pair) - a cable in which twisted pairs are enclosed in a common foil shield, as well as SFTP (Shielded Foil Twisted Pair) - a cable in which the common shield consists of foil and braids.

Shielded twisted pair(EVP), she STP(Shielded Twisted Pair), has many varieties, but each pair must have its own screen:

STP with a designation like "Type xx" is a "classic" twisted pair cable introduced by IBM for TokenRing networks. Each pair of this cable is enclosed in a separate foil screen (except type 6A), both pairs are enclosed in a common braided wire screen, outside, everything is covered with an insulating stocking, impedance - 150 ohms. Wire can be 22-26 AWG solid or stranded. Single core 22 AWG cable can have a bandwidth of up to 300 MHz.
Category 5 STP is a common name for a 100 ohm impedance cable that has a separate shield for each pair, which can be of various designs (foil, braid, combination of both). Sometimes under the same name there is a cable, which has only a common screen (AMP),
SSTP (Shielded- Screened Twisted Pair) category 7 - a cable similar to PiMF.

Cables can have different impedance ratings. The EIA/TIA-568A standard defines two values - 100 and 150 ohms, standards IS01 1801 and EN 50173 add 120 ohms. Requirements for impedance accuracy in the operating frequency band are usually in the range of ±15% of nominal. Note that UTP cable most often has an impedance of 100 ohms, and shielded STP cable originally existed only with an impedance of 150 ohms. Currently, there are types of shielded cable with an impedance of 100 and 120 ohms. Terminal equipment is available in versions for both shielded (STP) and unshielded (UTP) twisted pair. With a cable that has at least one shield (STP, ScTP, FTP, PiMF), connectors are used to provide shield connection and (not always) shielding. The impedance of the cable used must match the impedance of the equipment it is connecting, otherwise interference from the reflected signal may cause the connections to fail. This is especially critical for high frequencies (100 MHz and above).

The most widespread are cables with a number of pairs of 2 and 4. There are also double designs - two cables of two or four pairs are enclosed in adjacent insulating stockings. The common stocking can also include STP+UTP cables. Of the multi-pair, 25-pair are popular, as well as assemblies of 6 pieces of 4-pair. Cables with a large number of pairs (50, 100) are used only in telephony, since the manufacture of multi-pair cables high categories- the task is very difficult. Each cable pair has its own twist pitch, which is different from the neighboring ones. This ensures a reduction in the mutual inductance and capacitance of the pair wires, and, consequently, a reduction in crosstalk. Since the wave characteristics of a pair (velocity, impedance, attenuation) depend on the twist pitch, the pairs in a cable are not identical. Each pair in a cable segment has its own “electrical length”, determined through the signal propagation time and nominal (for this cable) wave propagation speed. The "electrical length" of the pair will be different from the "mechanical" measured with a tape measure. Sometimes a variable twist pitch is used for each pair - this equalizes the average parameters of the pairs while maintaining an acceptable level of crosstalk.

According to the caliber - the cross section of the conductors - the cables are marked in accordance with the AWG standard (American Wire Gauge - American wire gauges). The main conductors used are 26 AWG (section 0.13 mm2, linear resistance 137 Ohm / km), 24 AWG (0.2-0.28 mm2, 60-88 Ohm / km) and 22 AWG (0.33-0, 44 mm2, 39-52 Ohm/km). However, the gauge of the conductor does not provide information about the thickness of the wire in the insulation, which is very important when terminating the ends of the cable into modular plugs, and the outer diameter of the cable, which can be used to calculate the cross section of the required cable channels.

Conductors can be rigid single-core (solid) or flexible stranded (stranded or flex), usually consisting of 7 wires (7-strand). Single core cable has better and more stable performance. It is used mainly for stationary wiring (it is cheaper than stranded), which is most of in cable lines. A multi-core flexible cable is used to connect equipment (subscriber and telecommunication) with fixed wiring and patch cords.

Connecting equipment

Connecting equipment provides the ability to connect to cables, that is, provides cable interfaces. For twisted pair, there is a wide range of connectors designed for both permanent and detachable connection of wires, cables and cords. Of the one-piece connectors, connectors of types S110, S66 and Krone, which are industry standards, are common. Among plug-in connectors, the most popular are standardized modular connectors (RJ-11, RJ-45, etc.). For termination, the insulation from the wires is not removed - it is displaced during the termination of the connector contacts by the knives themselves. The procedure for terminating (terminating) wires into connectors of types S110, S66, Krone and the like using special percussion instruments is also called punching (punch down), and blocks with these connectors are called PDS (Punch Down System).

Connecting equipment also includes various adapters that allow you to join different types of cable interfaces.

Modular Jack (sockets, sockets) and Modular Plug (plugs) are the most commonly used connectors for 1-, 2-, 3-, 4-pair category 3-6 cables. Cable systems use 8- and 6-position connectors, better known as RJ-45 and RJ-11, respectively.

The designation RJ (Registered Jack - registered jack) actually refers to a connector with a specific wire layout and comes from telephony. Each of the jacks shown in the figure can be used with different RJ numbers.

RJ-45 modular plug

When installing a structured cable system For data transmission, use 8-way connectors with EIA/TIA-568A, abbreviated T568A, or EIA/TIA-568B, abbreviated T568B.

The disadvantage of all layouts is that at least one pair is not cut into adjacent contacts, but another pair is wedged inside it. This leads to an increase in crosstalk and signal reflection from the inhomogeneity that occurs when the wires of these pairs are more untwisted. For this reason, the use of conventional modular connectors for categories above 6th is problematic. The most common modular connectors are category 5 or 3, category 5 and higher connectors are also available for shielded wiring.

Category 5 and higher modular sockets always have the corresponding designation; they differ markedly from category 3 sockets in their design and the method of connecting wires. Here, the socket itself is mounted on a printed circuit board, on which blade contacts (such as S110, Krone or other design) are also installed to terminate the cable wires. The circuits are routed with printed conductors so that the wires of each pair are connected to adjacent contacts of the connector. In addition, there are reactive elements on the board that match the impedance, made printed. Without these elements, on high-speed technologies (100 Mbps and above), problems associated with the reflection of signals from the connectors are possible.

modular socket

According to the design and method of mounting sockets, there are many options that can be divided into fixed configurations and typesetting (modular) systems. Fixed configuration sockets - wall-mounted for 1 or 2 of the same type sockets and blocks of 4, 6 or 8 sockets for patch panels - usually mounted on printed circuit board on which they are mounted. To protect against dust, sockets with hinged covers or retractable spring-loaded shutters are used. For patch panels, the socket is best placed in the front position (plug enters from the front). For workplace outlets, the outlet can look both down and sideways (up is undesirable due to dust accumulation). Convenient in many cases corner sockets. There are many mounting options, and with the outward similarity of sockets from different manufacturers, they often do not fit “non-native” fittings, it would seem, with the same dimensions.

The termination of wires into sockets is carried out with a tool corresponding to the type of connector (S110, Krone), or with the help of protective caps. There are designs of sockets assembled without tools - the wires are laid out in a plastic cover, and when it is put on, they go into the contact knives.

Modular Plugs different categories outwardly may almost not differ from each other, but have different design. Category 5 plugs may have a separator that is slipped over the wires prior to assembly and crimping of the connector, which reduces the length of the untwisted part of the cable and facilitates the laying of wires. Contacts during installation (crimping) cut into the wires through the insulation. Plugs for solid and stranded cables differ in the shape of the contacts. Needle contacts are used for multi-core cable, the needles are stuck between the conductors of the wires, providing a reliable connection. For single core cable contacts are used that “hug” the core on both sides. During crimping, the protrusion that fixes the cable is also pressed in (the part that is still in the stocking). The latch is used to snap the plug into the socket.