twisted pair- This is a type of communication cable, which is presented in the form of a pair of conductors covered with insulation and twisted together with a certain pitch. Twin conductors are combined into multi-pair wires, which are covered with a common protective sheath.
Depending on the twisting pitch of the pairs, the number of double cores, the material of the outer coating, the type of insulation and shielding, the area of \u200b\u200buse of the wire is determined. Such wires are part of a structured cabling system, therefore they are widely used in telecommunications, video surveillance, and computer networks.
To build a local home or office network, the 5e FTP cable is most often used. If you decide to create your own local computer network in the apartment, or for other reasons you need a twisted pair cable, then you should figure out which type you need to purchase.
Twisted pair by shielding type
Shielding is the protection of conductors (or cores) from exposure electromagnetic radiation, which can affect the transmitted data and speed.
There are several types of cable, depending on how the cores are shielded inside.
Unshielded UTP wire
The cheapest type, limited in its use due to instability to crosstalk and EMP. Represents one or more pairs, united by an outer shell.
Shielded FTP cable
More protected from EMP in that it has a common shield that covers all the cores with foil. It is the most popular type of cable used almost everywhere. It is slightly more expensive than UTP, but it ensures the integrity of the transmitted data.
Double shielded STP cable
This type uses double protection, that is, there is a common screen for all foil cores, plus a separate screen for each pair. One of the most reliable cables, several times more expensive than UTP and FTP, most often used in offices and in production.
Many organizations use funny cable shield markings. If you have to look for a twisted pair cable via the Internet and in markets, then you may encounter the following designations:
- F / UTP - twisted pair with a common shield;
- U / UTP - completely without a screen;
- SF / UTP - a pair with a double screen;
- S / FTP - in it the common shield is presented in the form of a copper braid, and the protection of each pair is made of foil.
As already noted, the most common use case is an FTP cable, the price of which depends on the manufacturer, the shielding material used and the quality of the outer protective sheath.
Twisted pair according to the type of sheath used
Pairs of cores twisted together are connected into a single cable using an external protective sheath. Usually it is made of polyethylene or polyvinyl chloride. This polymer has excellent resistance to most solvents, alkalis and oils, does not emit toxic fumes in air and does not break down in the temperature range from -15 to +66 degrees Celsius.
In its pure form, it has excellent ductility, therefore, so that the cable can be easily bitten or broken along if necessary, chalk is added to PVC. Together, they make an excellent material for the manufacture of a protective shell.
The two main components can be mixed with various additives that provide the desired properties of the external part on the FTP cable. Based on them, the shell is divided into types, which are distinguished by colors.
Low-smoke non-combustible casing
Orange - made of non-flammable polymer, has the highest fire safety rating. Marked LSZH (stands for Low Smoke Zero Halogen - low smoke emission, zero halogens).
For outdoor use
Black - it contains the same polymer, but it has an additional protective layer of polyethylene, which is designed to protect the cable from external atmospheric influences, usually wires with such a sheath are used for laying on the street, in the sewer or through the air.
For indoor installation
Gray is a common budget sheath used for indoor cable. It is rather fragile for fracture and tear, which allows you to quickly break it in the right place.
There is always a marking on the shell indicating the type of shielding, manufacturer and category. Information is printed on the FTP cable every meter, foreign ones may have a foot. With its help, you can easily measure the desired length or find out the length of the laid lines by a simple calculation.
As a rule, cables are flat and round; round ones are used in everyday life and office premises (not counting telephone noodles, which can be seen less and less). For its installation, boxes or cable channels in baseboards are provided, and there are also semicircular mounts that allow you to nail the cable to the wall without damaging it.
Categories of cables by number of pairs and throughput
As already mentioned, there can be one twisted pair or several twisted pairs inside the cable. Depending on their number and bandwidth, the FTP cable has different categories.
Legacy Twisted Pair Categories
Cat1 - operating frequency 100 kilohertz, used to transmit a voice signal, popularly called "telephone noodles".
Cat2 - the frequency used is 1 megahertz, has the ability to transfer data up to 4 Mbit / s, contains 2 pairs of conductors, is not currently used anywhere.
Cat3 - operates at a frequency of 16 megahertz, maximum speed transmission up to 10 Mbit/s, contains 4 pairs, can be used in telephone and computer networks with a length of no more than 100 m.
Cat4 - used frequency band up to 20 megahertz, transmission rate up to 16 Mbit / s, contains 4 pairs and is not currently used anywhere.
Commonly used categories of twisted pair
Cat5e is the most popular FTP cable containing 4 pairs of conductors. Operates at a frequency of up to 125 MHz, when using 2 pairs it provides a transfer rate of up to 100 Mbit / s, when using all pairs up to 1 Gbit / s per second.
Cat6 - operating frequency up to 250 megahertz, has 4 pairs of cores and, when using all of them, provides speeds up to 1 Gbit / s per second, at a distance of up to 50 meters it passes up to 10 Gbit / s.
Rarely used perspective categories
Cat6a - has an operating frequency of up to 500 megahertz and 4 pairs of wires, provides a transfer rate of up to 40 Gbit / s. Used to build high speed lines.
Cat7 is a four-pair cable with an operating frequency of up to 700 megahertz and a transmission rate of up to 50 Gbit/s.
Cat7a - 4 pairs, frequency up to 1200 megahertz, can provide speeds up to 100 Gbit / s with a length of no more than 15 meters, and up to 10 Gbit / s when using all pairs.
How to choose the right twisted pair cable for home use
The most common cable is Category 5e twisted-pair FTP. With it, local networks are laid in offices and at home, it is used to connect computers to a router or hub. And, most likely, the cable that is laid to your apartment will be of the same category.
Some providers save on twisted pair and extend to their customers budget options no shielding at all. Unshielded twisted pair can be laid inside the apartment, if it is possible to lay the network away from the wiring and hide it in the cable channel.
Based on the foregoing, a conclusion can be drawn. In order to choose the right twisted pair cable, you need to decide on:
- Required data rate.
Most providers do not offer tariffs with speeds higher than 100 Mbit / s. However, if your equipment allows, then you can build a local network with a speed of up to 1 Gbit / s per second.
- The need for cable shielding.
By running the wire in the baseboard, away from electrical wiring, subwoofers, and other EMI emitting devices, you can get away with UTP to save money. It is still recommended to use an FTP cable or at least F/UTP.
- The place of laying the installation, where it passes, on the street or indoors.
If on the street, you will have to buy a secure cable, which costs an order of magnitude more expensive. For laying in an office, apartment or private house, it is enough to use a regular gray cable. Before installation in an office space, check the fire safety requirements.
Having studied what twisted pair is and what types it comes in, you can easily choose the cable that is right for your conditions. Do not forget that right choice FTP cables are only half the battle, you still need to learn how to crimp correctly and how many strands to use.
For these purposes, you can also invite a specialist who will come with necessary equipment, crimp the cable and set up all the computers. Or you can check how the crimping was done on the wire that the provider brought to the apartment, and do it in the same way.
An electrical signal can be transmitted to the recipient via a communication channel in the form of a wire or cable line. During the propagation of a carrier wave in a communication channel, the transmitted signal can be distorted, affected by noise and interference of a natural and industrial nature. Minimization of the effect of distortion and noise is achieved by choosing the modulation method, frequency and power of the carrier wave, and other factors.
The advantage of the analog way of presenting and transmitting a message is that the analog signal can, in principle, be an absolutely exact copy of the message. The disadvantages of the analog method are, as often happens, a continuation of its advantages. An analog signal can have any shape, so if, for example, noise was added to the signal during recording, it is very difficult and often impossible to distinguish the original, or recorded, signal against the background of noise. The analog method has the effect of accumulating distortion and noise, which can limit the expansion of functionality. analog systems. Analogue communication technology has come a long way with improvements and has reached a high level. However, further expansion of the functionality and improvement of the quality indicators of analog equipment is associated with costs that can make new equipment inaccessible to the mass consumer audience. Now analog technology is giving way to digital systems.
From the point of view of circuitry, digital equipment is more complicated than analog, however, its functionality much wider, and some of them are fundamentally unattainable with analog signal processing.
To transmit continuous messages using a digital communication system analog signals, displaying continuous messages, must be sampled and quantized.
Digitization of a signal is always associated with the appearance of noise and the occurrence of distortions (frequency, non-linear, as well as some specific distortions). However, analog-to-digital conversion is performed only once in a digital communication system. The digital signal can then undergo any number of processing and transformations, without introducing additional distortion and noise.
Historically, the first lines for signal transmission, from the primitive wire telegraph to modern coaxial lines, were unbalanced.
The transmission of signals over a coaxial cable is called unbalanced transmission, since the coaxial cable closes the loop between the source and the receiver, where the central core of the cable is the signal wire, and the shield is the ground wire. Despite being well shielded, coaxial cable is susceptible to interference and therefore cannot transmit composite and component video signals over long distances. In addition, the coaxial cable requires the output impedance of the source and the input impedance of the receiver to be matched to its characteristic impedance, Special attention you have to pay attention to the layout of the cable and the termination of the connectors.
Since the life and work of a modern person is literally saturated with electronic equipment, it is clear that the problem of electromagnetic compatibility, protection of signal transmission lines from noise and interference will only become more complicated.
Further improvement of cable shielding gives an insignificant effect with a simultaneous significant increase in their cost, so a fundamentally new technical solution. And it was found through the development of balanced signal transmission or balancing circuits.
With balanced signal transmission, all electromagnetic interference and noise equally affect both signal wires of the line. When the signal reaches the receiving end of the line, it enters the input of a differential amplifier with a well-balanced common-mode rejection factor (CMRR).
If two wires have similar characteristics and enough twists per meter (the more, the better), they will be equally affected by noise, voltage drop, and pickup. An amplifier with good CMRR at the receiving end of the line will eliminate most of the unwanted noise.
Twisted-pair cable is usually cheaper than coaxial cable, it is easier to lay out, and stripping connectors is not a problem.
Balanced signal transmission
The idea of balanced signal transmission is that it uses three, not two wires (as in unbalanced lines) (Fig. 1). Input signal before applying to the line, it is inverted so that the signal U r2 differs in phase from the signal U r1 by 180 degrees. It is clear that the noise and interference induced in both signal wires of the line will have the same amplitude and phase.
A differential amplifier is installed at the output of the line, which is designed in such a way that it amplifies the signals that come to its inputs in antiphase and suppresses common-mode signals.
Rice. 1. Balanced signal transmission
It can be seen from the figure that two common-mode noise voltages are connected in series with the conductors of the signal lines U w1 And U w2 , which cause the appearance of noise currents I Ш1 And I SH2 . Sources U G1 And U G2 together create a signal current I G . In this case, the total voltage on the load will be
U H = I w1 R H1 - I w2 R H2 + I G (R H1 + R H2 )
The first two terms on the right side of the equation are the noise voltages, and the third term is the useful signal voltage. If I Ш1 equals I SH2 And R H1 equals R H2 , then the noise voltage at the load is zero:
U H = I G (R H1 + R H2 )
i.e. noise and/or interference cancel each other out.
The degree of circuit symmetry, or common mode rejection ratio (CMRR), is defined as the ratio of the common mode noise voltage to the differential noise voltage it causes, and is usually expressed in decibels (dB).
The better the symmetry of the circuit, the more noise reduction can be obtained. If it were possible to achieve perfect symmetry, no noise could enter the system at all. From a well-designed system, 60-80 dB symmetry can be expected. It is possible to achieve better symmetry, but this usually requires special cables and may require individual circuit adjustments.
ADVICE
Use balancing in combination with shielding where the noise level must be below the level achievable with shielding alone, or even instead of shielding.
Like any technical solution, balancing signal transmission lines has its drawbacks.
- A balanced transmission line is more complicated and more expensive than an unbalanced one, since it requires a transmitter and a balanced signal receiver;
- If the noise level is too high, the balanced signal receiver may enter saturation mode and the signal transmission will stop;
- Due to the attenuation of the signal in the cable, it is necessary to install intermediate amplifiers, which introduce additional cumulative distortions;
- When using intermediate amplifiers, signal correction may be required.
Cables for transferring balanced signals
A "twisted pair" is a copper-based cable that combines one or more pairs of conductors in a sheath. 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.
Each pair consists of two insulated copper wires twisted around each other. Twisted pair cables vary greatly in quality and transmission capabilities. Correspondence of cable characteristics to a certain class or category is determined by generally recognized standards (ISO 11801 and TIA-568). The characteristics themselves directly depend on the structure of the cable and the materials used in it, which determine the physical processes that take place in the cable during signal transmission.
Rice. 2. Appearance unshielded twisted pair cable
The design of a twisted pair cable is clear from the figure.
Caliber determines the cross section of the conductors. Cables and wires are marked in accordance with the AWG (American Wire Gauge) standard. The most commonly used conductors are 26 AWG (section 0.13 mm 2), 24 AWG (0.2 - 0.28 mm 2) and 22 AWG (0.33 - 0.44 mm 2). However, the gauge of the conductor does not give information about the thickness of the wire in the insulation, which is very important when terminating the ends of the cable into modular plugs.
Thickness isolation- about 0.2 mm, the material is usually polyvinyl chloride (English abbreviation PVC), for higher quality samples of category 5, polypropylene (PP) or polyethylene (PE) is used. The highest quality cables are insulated with foamed (cellular) polyethylene, which provide low dielectric losses, or Teflon, which ensures cable operation over a wide temperature range.
Breaking thread(usually made of nylon) is used to facilitate the cutting of the outer sheath: when pulled, it makes a longitudinal cut on the sheath, which opens access to the cable core, without damaging the insulation of the conductors.
Outer shell has a thickness of 0.5-0.6 mm, and is usually made of polyvinyl chloride with the addition of chalk, which increases its fragility. This is necessary to obtain an accurate break at the place of the incision with the blade of the cutting tool. In addition, so-called "young polymers" are beginning to be used, which do not support combustion and do not emit toxic halogen gases when heated. Their widespread introduction is hindered only by a higher (by 20-30%) price.
The most common shell color is grey. An orange color generally indicates a non-combustible sheath material.
In addition to information about the manufacturer and type of cable, its marking necessarily includes meter or foot marks.
Cable core design quite varied. In inexpensive cables, the pairs are laid in a sheath "haphazardly". Better options include a pair (two pairs between each other) or a quadruple twist (all four pairs together). The latter option makes it possible to reduce the thickness of the core and achieve better electrical characteristics.
Category(Category) of twisted pair determines the frequency range in which its application is effective. There are currently standard definitions for 5 cable categories (Cat 1 to Cat 5), but Category 6 and Category 7 cables are already being produced.
Color coding is used to identify pairs within a cable. So the first four pairs have the base colors, respectively: Blue, Orange, White and Brown. Most often, the main wire in a pair is completely painted in the base color, and the additional wire has a white insulating sheath with the addition of stripes of the base color.
Shielded twisted pair (Shielded Twisted Pair, STP) well protects transmitted signals from external radiation, and also reduces power loss in the cable in the form of radiation. Shielded twisted pair has many varieties.
ADVICE
The presence of a screen requires high-quality grounding during installation work, which complicates and increases the cost of cable systems at the STP, but with the correct grounding of the screen, it provides better electromagnetic compatibility of the cable system with other sources and receivers of interference
However, incorrect grounding of the screen can also lead to the opposite result. In addition, the presence of a shield that needs to be grounded at both ends of the cable can cause the problem of ensuring the equality of the "ground" potential at spatially separated points.
Cables on unshielded twisted pair (Unshielded Twisted Pair, UTP) are currently the main transmission medium for non-optical technologies. The cable combines good electrical and mechanical characteristics with ease of installation and relatively low cost.
The classification of twisted pair cables is shown in Table 1.
* Not standardized.
Category 1 cables used where the requirements for transmission speed are minimal. Usually these are cables for transmitting signals in the audio range and low-speed (tens of Kbps) data transmission. Until 1983, UTP cat.1 was the main cable for telephone wiring in the United States.
Category 3 cables were standardized in 1991. With a bandwidth of 16 MHz, this cable was used to build high-speed networks for that time, and now the cable systems of many buildings are built on UTP cat.3, which is used for both data transmission and audio signal transmission.
Category 4 cables are an improved version of UTP cat.3 - their bandwidth is extended to 20 MHz, noise immunity is improved and losses are reduced. In practice, these cables are rarely used; mainly where it is necessary to increase the length of the line from the usual 100m to 120-140m.
Category 5 cables specifically designed to support high speed computer technologies such as FastEthernet and GigabitEthernet. The bandwidth of the cable category 5 is 100 MHz. Category 5 cable has now replaced UTP cat.3 and is the backbone of all new cabling systems.
A special place is occupied by category 6 and 7 cables, which are produced relatively recently and have a bandwidth of 200 and 600 MHz, respectively. Category 7 cables must be shielded; UTP cat.6 may or may not be escaped. They are used in high speed networks on segments longer than UTP cat.5. These cables are much more expensive than category 5 and are close in cost to fiber optic cables. In addition, they are not yet standardized and their characteristics are determined only by company standards, which causes problems when testing the cabling system (the EIA / TIA-568A standard TSB-67 test specification does not include cables of the 6th and 7th categories) .
Some companies already produce Category 8 twisted-pair cables. They are designed for data transmission at frequencies up to 1200 MHz (broadband systems cable television And modern applications SOHO type). The cable consists of 4 individually shielded twisted pairs, overall braided, sheathed with LSZH material for indoor use. Thanks to the individual shielding of the pairs with aluminum foil, the cable has extremely high NEXT values. Cables of this category are characterized by stable values of wave impedance and attenuation, as well as the absence of resonance at frequencies up to 1200 MHz.
Category 8 cables meet the stringent requirements of ISO 11801 (2nd edition) and exceed the requirements of ISO/IEC 11801 for classes D, E, F and IEC 61156-5, IEC 61156-7 (CVD) for categories 5e, 6 and 7 .
STP with the type designation “Type xx” is a “classic” twisted pair cable developed by IBM for TokenRing computer networks. Each pair of this cable is enclosed in a separate foil shield, both pairs are enclosed in a common braided wire shield, everything is covered with an insulating stocking on the outside, the impedance is 150 ohms. Common cables are STP Type1 - solid 22 AWG, STP Type 6 - stranded 26 AWG, and STP Type 9 - solid 26 AWG. Cable Type 6A used for patch cords does not have individual pair shielding.
ScTP(Screened Twisted Pair) - a cable in which each pair is enclosed in a separate screen.
FTP(Foilled Twisted Pair) - a cable in which twisted pairs are enclosed in a common foil shield.
PiMF(Pair in Metal Foil) - a cable in which each pair is wrapped in a strip of metal foil, and all pairs are wrapped in a common shielding stocking. Compared to the "classic" STP, this cable is thinner, softer and cheaper (although you can't say the same about the 600 MHz PiMF cable).
Cables can have different impedance ratings. The EIA/TIA-568A standard defines two values - 100 and 150 ohms, the ISO11801 and EN50173 standards also add 120 ohms. Note that UTP cable almost always 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. 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.
The most widely used cables are 2-pair and 4-pair 24 AWG cables. Of the multi-pairs, 25-pairs are popular, as well as assemblies of 6 pieces from 4-pairs.
Cables are most often round - in them the elements are collected in a bundle. There are also special flat cables for laying communications under carpets (Undercarpet Cable), among which there are cables of categories 3 and 5.
Conductors can be rigid solid (Solid) or flexible stranded (Stranded or Flex).
ADVICE
For fixed installations, use a cable with solid wires, which usually has better and more stable characteristics.
To connect subscriber equipment, and switching uses flexible cables (cords, patch cords).
Patch cord(patch cord) is a piece of multi-core 4-pair cable 1-10 m long with RJ-45 plugs at the ends.
To ensure resistance to constant bending, their conductor is made not from one, but from seven thinner copper wires with a thickness of about 0.2 mm each (multi-wire design). The same purpose is served by a thicker (up to 0.25 mm) insulation, and an outer shell of increased flexibility.
Due to the greater attenuation compared to the usual attenuation, it is justified to use a cable for cords only for short distances, as a rule, no more than 5 meters on each side of the line.
Cables are interconnected using connectors. The connector provides mechanical fixation and electrical contact. Like cables, they are classified into categories that determine the operating frequency range.
For twisted pair, modular connectors (Modular Jack), commonly known as RJ-45, are widely used: sockets (Outlet, Jack) and plugs (Plug). The abbreviation RJ itself stands for Registered Jack.
Rice. 4. RG-45 cable connector
Category 5 sockets (they must have a corresponding designation) differ from category 3 sockets in the way of connecting wires: in category 5, only wire clamping with a knife connector (type S110) is allowed, in category 3, screw clamping is also used. In addition, on the category 5 socket board there are matching reactive elements with normalized parameters, made by printing. It is difficult to determine the category of modular plugs at a glance. Plugs for solid and stranded cables differ in the shape of the pins. For shielded wiring, sockets and plugs must have shields, either solid or only providing a connection between the shields of the cables.
For switching cable channels and connecting network equipment, patch panels are used (Fig. 4), which are produced by many companies, and wall sockets (Fig. 5).
Main characteristics of twisted pair
The characteristics of a twisted pair cable directly depend on the structure of the cable and the materials used in it, which determine the physical processes that take place in the cable during signal transmission.
Rice. 7. Twisted Pair Balance Explained
The balance of a pair is actually a defining quality characteristic of a cable, as it affects most of its other properties. The fact is that an electromagnetic (Electro Magnetic - EM) field induces an electric current in the conductors and is formed around the conductor when an electric current flows through it. The interaction between EM fields and current-carrying conductors can have a negative effect on signal transmission quality. In both conductors of a balanced pair, electromagnetic interference (em1 and em2) induce signals of the same amplitude, (S1 and S2) that are in antiphase. Due to this, the total radiation of the "ideal pair" tends to zero.
If there is more than one pair in the cable, then in order to exclude mutual interference of pairs that could upset the electromagnetic balance, the pairs are twisted with different pitches.
Like any conductor, a twisted pair has resistance to alternating electric current ( characteristic impedance). For different frequencies, this resistance may be different. A twisted pair has an impedance of typically 100 or 120 ohms. Particularly for Cat. 5 in the frequency range up to 100 MHz, the impedance should be 100 ohms +15%.
For an ideal pair, the impedance should be the same along the entire length of the cable, since in places of inhomogeneity, the effect of signal reflection occurs, which in turn can degrade the quality of information transmission. Most often, the uniformity of the impedance is violated when the twist pitch changes within one pair, the cable bends during laying, or another mechanical defect.
Rice. 8. Graph of the characteristic impedance
Signal speed/delay NVP (Nominal Velocity of Propagation) - signal propagation speed. Often used is the derivative of NVP and cable length, the "delay" characteristic (delay), expressed in nanoseconds per 100 meters of a pair. If there is more than one pair in the cable, then the concept of "delay skew" or delay difference is introduced. The reason for its occurrence is that the pairs cannot be perfectly identical, which gives rise to different signal propagation delays in different pairs.
An important characteristic of a twisted pair cable is Attenuation, which characterizes the amount of signal power loss during transmission. It is calculated as the ratio of the power of the signal received at the end of the line to the power of the signal fed into the line. Since the amount of attenuation changes with increasing frequency, it must be measured over the entire range of frequencies used. The value itself is expressed in decibels per unit length.
Rice. 9. Signal attenuation in twisted pair
The graph below shows the signal power loss during transmission as a function of cable length and signal frequency.
Another important parameter is NEXT(Near End Crosstalk), or crosstalk between pairs in a multi-pair cable, measured at the near end - that is, from the side of the signal transmitter, which characterizes crosstalk between pairs. NEXT is numerically equal to the ratio of the signal applied to one pair to the received induced signal in the other pair and is expressed in decibels. NEXT is all the more important the better the pair is balanced.
Rice. 10. Crosstalk measurement
In addition to estimating the mutual interference of pairs at the near end of the cable, crosstalk is also measured from the side of the signal receiver. This test is called FEXT (Far End Crosstalk).
ACR(Attenuation Crosstalk Ratio) One of the most important characteristics that reflects the quality of a cable is the difference between linear and crosstalk attenuation, expressed in decibels. The lower the attenuation per unit length, the greater the amplitude of the useful signal at the end of the line. On the other hand, the greater the crosstalk, the less mutual interference of pairs. Thus, the difference between these two values reflects the real possibility of isolating the useful signal by the receiving device against the background of interference. For reliable signal reception, it is necessary that the Attenuation Crosstalk Ratio is not less than the specified value, determined by the standards for the corresponding cable category. When the linear and crosstalk attenuation are equal, it becomes theoretically impossible to isolate a useful signal.
Return Loss (RL) When a signal is transmitted, there is a so-called signal reflection effect in the opposite direction. The amount of reflection of the Return Loss signal or "reverse attenuation" is proportional to the attenuation of the reflected signal. The characteristic is especially important when building communication lines that use twisted-pair signal transmission in both directions (full duplex transmission). A sufficiently large amplitude reflected signal can distort the transmission of information in the opposite direction. Return Loss is expressed as the ratio of the power of the direct signal to the power of the reflected signal.
Rice. 11. Explanation of the fading effect
How to cut a twisted pair cable
1. It is necessary to cut the cable evenly at a distance of 5-10 centimeters from its end. Even if the old cut looks good, it is possible that moisture or dirt has penetrated under the shell.
Rice. 12. Stripping the cable sheath
Rice. 13. RJ-45 connector and wire crimping procedure
Rice. 14. Aligning the conductors before inserting into the connector
Rice. 15. RJ-45 connector crimp
Rice. 16. Crimped RJ-45 connector on the cable
Rice. 17. Straight and cross cable
2. Approximately half an inch (1.25 cm) of conductors must be removed from the sheath to install the connector. Most crimping tools have a special tool for this - a pair of blades and a limiter. Insert the end of the cable into the tool until it stops and cut the insulation. Just cut, not cut, because it is important not to damage the cable cores. The shell can be easily removed along the incision line.
3. In principle, it makes no difference which of the pairs of the cable will be connected to which pins of the connector. The main thing is that it is pairs that are connected, and not conductors from different pairs, however, there is a generally accepted standard EIA / TIA-568B, and it is better to follow it. Pairs are connected to pins 1-2, 3-6, 4-5, 7-8 of the RG-45 connector. To sort the conductors, pairs will inevitably have to be untwisted. This must be done to a minimum length (according to the standard, not more than 1.25 cm), violating the structure of the pairs, the geometric dimensions and the laying pitch of the part of the cable that is not involved in the connector as little as possible.
4. After the conductors are evenly laid and straightened, you need to align the edge by cutting them.
5. Carefully insert the conductors into the connector. Each core must fit into its groove inside the RJ-45 connector until it stops, which can be checked through the transparent housing of the connector. If any conductor has not reached the end, you need to pull the entire cable out of the connector and start over.
6. Tighten the edge of the cable sheath into the connector housing by the latch so that after crimping the sheath is held by the connector.
7. Before crimping, make sure that all cores and cable sheath are correctly positioned. After that, insert the connector into the socket on the tool, and smoothly, in one motion, crimp the connector. The sharp edges of the contacts will cut through the insulation and provide reliable contact, and the latch will be recessed into the housing, additionally securing the cable.
8. The connector is ready. Before use, it is advisable to inspect it, paying particular attention to the condition of the contacts. All of them should protrude from the body to an equal height.
9. The other end of the cable is crimped in the same way. There are two types of cables: straight (pins 1-2 and 3-6 of the first connector are connected to pins 1-2 and 3-6 of the second) and crossover (pins 1-2 and 3-6 of the first connector are connected to pins 3-6 and 1 -2 second).
If a video or audio signal is transmitted over a twisted pair cable, a straight cable is used, but if control signals are transmitted, a crossover cable is used.
The physical meaning is quite simple - the transmitter of one device must be connected to the receiver of another. Therefore, to connect the same devices (for example, two computers), you need to use a crossover cable.
ADVICE
For additional protection of the cable and latch of the RJ-45 connector from mechanical damage, use a protective cap on the connector. A simple and cheap measure, which, unfortunately, is often neglected.
Rice. 18
Interface extensions
In modern installations, twisted-pair cables are often used to carry VGA signals over considerable distances. In order to ensure that the signal is not “lost” against the background of noise and interference, interface extenders (extender or line transmitter) are used, modern models of which provide signal transmission to the required range with a low level of interference over twisted pair. Such an effective and inexpensive technical solution is used in many areas: in information systems in transport, educational institutions or hospitals. The VGA signal extender operates at the hardware level, so it is free from any compatibility issues software, codec negotiation or format conversion.
Until recently, it was possible to transmit signals without loss of quality over relatively short distances over twisted pair, but this year the situation has changed dramatically after a new line of extension cords for working with twisted pair appeared on the market. Thanks to the new element base, as well as new hardware and circuit solutions, a real breakthrough has been achieved: now signals can be transmitted without loss of quality over distances exceeding 300 meters. The equipment is capable of stable operation with conventional Category 5 unshielded twisted pair, but much better results can be obtained with higher quality cables.
The new line of equipment includes XGA twisted-pair signal transmitters, distribution amplifiers, switches, and twisted-pair signal receivers.
If we consider a passive line (i.e. a line without an active terminal equipment), then an RG-59 cable is capable of transmitting composite video, a PAL or NTSC television signal without distortion visible on the screen only at 20-40 m (or up to 50-70 m via RG-11 cable). Specialized cables such as Belden 8281 or Belden 1694A will increase the transmission distance by about 50%.
For VGA, Super-VGA, or XGA signals received with graphics cards computers, regular VGA cable provides image transmission with a resolution of 640x480 at a distance of 5-7 m (and with a resolution of 1024x768 and higher, such a cable cannot be longer than 3 m). High quality industrial VGA/XGA cables provide a range of up to 10-15, rarely up to 30 m. In addition, the communication line will be subject to loss on high frequencies(High frequency loss), which manifest themselves in a decrease in brightness until the color disappears completely, a deterioration in resolution and clarity. To eliminate this problem, VGA / XGA extenders use a high-frequency loss control scheme called EQ (Cable Equalization, cable correction) or HF (High Frequency) control. The EQ circuitry provides frequency dependent signal amplification to "flatten" the frequency response.
The transmitter on the extender usually converts the video signals to a differential symmetrical format most suitable for twisted pairs. The receiving side restores the standard video format to display the received signal on the monitor.
Rice. 19. A set of equipment for converting video and audio signals
stereo signals into signals for transmission over twisted pair over long distances
On fig. 17 shows a set of equipment for converting video and audio stereo signals into signals for transmission over twisted pair over remote distances. With these devices, a single twisted-pair cable is sufficient to transmit three signals (1 video and 2 audio). The equivalent load switch allows you to connect several of these devices to work with receiving devices. A twisted-pair line may have taps, but this will not affect the picture quality.
The receiver and transmitter operate on the same frequency and have the same frequency range. With this device it is allowed to use cable lines with a length of several hundred meters. Broadcast signal quality is ensured with a cable length of up to 100 m.
Transmission distance limits for analog and digital video and audio signals can be summarized in a table.
| Signal type | Signal type | Bandwidth, MHz | Distance, m |
| Composite | analog | 6 | 300 |
| S-Video (2 pairs) | analog | 6 | 300 |
| Component VGA/XGA (4 pairs) | analog | 380 | up to 100 |
| Audio balanced | analog | 0,02 | up to 200 |
| DVI-D | digital | 6 | 5 |
| IEEE 1394 | digital | 400 (800) | 10 |
Since audio signals have a relatively small spectrum width, the problems of high-frequency attenuation of the signal in the line are not significant for them, therefore, in principle, old cheap twisted pair cables of category 3 can also be used for them.
Cables for digital signal transmission with DVI and IEEE 1394 interfaces, in principle, differ little in their design from twisted pair cables, therefore they are also included in Table 2. However, transmission digital signals Compared to analog, it has a number of significant features. High noise immunity is achieved through the use of special signal coding technologies, for example, T.M.D.S. in DVI.
The definition of the twisted pair category is based on the maximum transmitted frequency range. This is due to the number of turns per unit length of the cable. That is, the higher the category, the greater the frequency range to be passed due to the increase in the turns of each twisted pair. Twisted pair categories are described in international and domestic standards.
The categories (CAT for short) of a twisted pair determine the calculated data rate. Besides LAN cable they are also divided into classes and are also taken into account when building a structured cabling system. Keep in mind that the higher class twisted pair supports the lower class technical capabilities. But twisted pair does not support the class below technical applications upper class. The higher the class, the better. transfer characteristics and above the maximum frequency of the cable line.
CAT1(frequency band - 0.1 MHz). It has one pair and is used to transmit voice and digital data with the participation of a modem. This is a standard telephone cable, which was once used in a "twisted" form in the United States, and is still used in Russia 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 outlived itself. Sometimes used in the construction of telephone networks. Previously seen on Arcnet and Token Ring networks. It has a data transfer rate up to 4 Mbps. Not suitable for building modern networks.
CAT3 (frequency band - 16 MHz. Class "C"). There are 2-pair and 4-pair twisted-pair types. It is used not only to create telephone, but also local networks based on 10BASE-T. Supports data transfer rates from 10 to 100 Mbps using 100BASE-T4 technology with 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 rates up to 16 Mbps are possible. Not used today.
CAT5(frequency band - 100 MHz. Class "D"). The cable was used to create telephone lines and build local networks 100BASE-TX, as well as in Ethernet (LAN). Supports data transfer rates up to 100 Mbps.
CAT5e(frequency band 125 MHz). This is an advanced twisted pair cable of the fifth category. Supports data rates up to 100 Mbps when using 2 pairs and up to 1000 Mbps 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.
CAT6(frequency band 250MHz. Class "E"). This is a common type of cable used in Fast Ethernet and Gigabit Ethernet networks. There are four pairs of conductors in the cable structure. Supports high data transfer rates up to 10 Gbps with a maximum length of 55 meters.
CAT6a(frequency band 500 MHz. Class "E A"). The cable structure consists of four pairs of conductors. It is used in Gigabit Ethernet networks and supports speeds up to 10 Gb / s at a distance of up to 100 meters.
CAT7(frequency band 600 - 700 MHz. Class "F"). Supports data transfer rates up to 10 Gbps. The structure of the cable has a common outer shield and foil protection for each pair. By type, refer to S/FTP (ScreenedFullyShieldedTwistedPair).
CAT7a(frequency band 1000 -1200 MHz. Class "F A"). Twisted pair speeds reach up to 40 Gbps at distances up to 50 meters and up to 100 Gbps at distances up to 15 meters.
| trunk cable, design features | |
| Twisted-pair cables, which have three or more four-pair elements under a common sheath, are multi-pair. 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, the conductors are made of solid copper wire. Unlike horizontal cable, backbone designs contain more than four twisted pairs and are therefore often referred to as multi-pair. Like horizontal cables, they are classified into categories 3 to 5, with category 4 backbone cables 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. | |
 | |
| Fig.4 Multi-pair trunk cables: a) 25-pair category 5 cable b) 300-pair category 3 cable | |
| In some designs, a central fiberglass rod is used as the basis of the core. The wires of one bundle are fastened with polyethylene ribbons. Outside, the core is protected by a common dielectric sheath. In addition to unshielded backbone cables, S/UTP designs are produced in limited quantities, in which there is a shield under the outer dielectric sheath that covers the cable core. Similar to horizontal cables, a marking is applied to their sheath, which includes 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 mass 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, a number of companies offer the so-called multi-element (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 the 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 cables of internal and external laying. The main difference between an external laying cable and an internal one is the use of special measures and design solutions to protect the cable core from moisture ingress into it. Most often, this problem is solved by using an outer polyethylene sheath. Some types of telephone cables have a helium-filled core void. Additional protection of the cable core against moisture and mechanical impacts is provided by armor made of aluminum or steel corrugated tape. |
twisted pair crimping
Twisted pair crimping is most often done with an 8P8C connector, more commonly referred to as RJ-45 (RJ45) in accordance with the color scheme corresponding to the purpose of the cable.
RJ-45 connector (on the left - for twisted-pair FTP/STP/SSTP, with a shielded case, on the right - UTP)
RJ-45 Twisted Pair Connector 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-switch or computer-hub, a straight cable is used, crimped on both sides equally, computer-computer or switch-switch (hub-hub) connections use a crossover cable (crossover, crossover) - on one side of the T568A, and on the other - T568B.
Crimping scheme for a 4-pair cable:
Crimping scheme for a 2-pair cable (the color of the pairs may vary depending on the cable manufacturer):
If you connect computers to each other directly 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 to 100% ground! If in doubt, it’s better not to do it at all, from “grounding” to a heating battery or an electrical panel housing, it can only get worse - and not only for the computer, but for you too!
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 hardware between themselves. With the help of which computers and other devices are connected to routers and modems. And also, with a cable called a twisted pair, most likely you have the Internet connected from the provider's equipment to your router, or directly to your computer. Also, almost all manufacturers of routers put a short network cable with their devices. It is needed to connect to the router different devices (PC, laptop, TV, game console etc.).
In the modern world, the development of data transmission technologies is taking place at a truly high pace. It is quite possible to say “at the speed of light”, because you will not surprise anyone with the transmission of information flows using optical fiber. But with all the positive functional characteristics of such communication cables, they have several serious drawbacks. The key ones are high cost and fragility.
On this moment it is necessary to try very hard to find a person who has absolutely no idea what the Internet is or has never used it. A huge number of people have a personal computer at home with access to the World Wide Web. But in order to "bring" the Internet to your home PC, you need to use a convenient, reliable, and most importantly strong cable. Here, for many years, a cable has come to the rescue, which received an incomprehensible, at first glance, name - twisted pair.
What is twisted pair?
Twisted pair is a special type of network cable. It is based on one or more pairs of insulated or twisted conductors. (the cable category depends on their number). The number of turns per certain unit of length is minimal, but sufficient to significantly reduce mutual guidance during signal transmission. From above, the twisted pair is usually covered with a protective plastic sheath.
Recently, this type of communication cable has become the most common in the creation of local and structured cable networks. This was due to its low cost and ease of laying.
The main disadvantage of twisted pair is significant signal attenuation. (to the level of unrecognizability) at distances over 100 meters. But this disadvantage 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) - copper mesh and aluminum foil are used.
However, in some types of shielded cable, protection may be used around each pair. This type of shielding provides better protection from various kinds of inductions, both internal and external.
Categories of twisted pair cable
In total, at the moment there are about 15 categories of twisted pair. They are numbered from CAT 1 to CAT 8.2. In most cases, the category is directly dependent on the number of pairs used to transmit information, as well as 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 uses only one pair. Applicable exclusively for voice transmission and making 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 Mbps. It was often used in token ring networks. Now rarely used in some telephone networks.
- CAT 3 is an improved version of the previous 2-pair cable. Designed to provide data transfer at speeds up to 10 Mbps. Now very often continues to be found in telephone networks.
- CAT 4 is another type of cable that is not used today. Consists of 4 pairs, has a transmission rate of up to 16 Mbps.
- 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 transmission speed varies from 100 Mbps (2 pairs are used) to 1000 Mbps (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.
- CAT 6 - 4 pairs are used for transmission, which allow you to increase the transmission speed to 10000 Mbps.
- CAT 6a - 4 pairs are used for transmission, which allow you to increase the transmission speed up to 10 Gb / s.
- CAT 7 - 4 pairs are used for transmission, which allow you to increase the transmission speed up to 10 Gbps. This category of cable must be shielded.
- CAT 8 is currently under development. Presumably, it will allow transmitting an information stream at a speed of up to 40 Gbit / s. Must have a common screen or screen for each pair.
Twisted pair crimping methods and schemes
Obviously, in order to connect the cable to various computer equipment or to switches and routers, the twisted pair must end in convenient and standardized connectors. This type of communication cable uses an RJ-45 connector (correct name 8Р8С, but we will use the usual).
In order for a twisted-pair network to work correctly, it is necessary to connect the contacts in the RJ-45 connectors in the appropriate order. This must be done both from one end and from 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 crimping schemes. There are only two of them: the direct crimp order and the cross crimp order (crossed).
- The first crimping scheme (straight) is used when connecting different types of equipment, for example, LAN card laptop and switch.
- The second crimping scheme (cross, or cross) is used when connecting the same type of equipment, for example, two laptops (sometimes to connect a computer to some old types of switches and hubs).
For crimping the cable, a special device is used - a crimper (pliers). I wrote about this in an article:.
And now directly about the order of crimping. Consider category 5 twisted-pair crimping circuits, 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.
- The 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.
- The 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: crimping scheme
- 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 order of contacts (from 1 to 8) - white-orange, orange, white-green, blue, white-blue, green, white-brown, brown.
For making gigabit crossover cable (supporting 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.
- The 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 cheap type of network cable.
It is becoming more and more difficult to understand in the accelerating modern flow of goods and technologies provided. First of all, this concerns computer technology and accessories for her. The latter include various types of information cables, in the names of the markings of which it is easy to get confused even by a specialist. In the article below, a study will be conducted, the purpose of which is to identify the main distinguishing properties of UTP, FTP, STP and other twisted pairs.
The meaning of information cable markings
In the modern market of structured cabling systems (SCS), there are many names of twisted pairs that are obscure to buyers: UTP, S / UTP, F / UTP, FTP, ScTP, STP, S / STP ... This list can be continued. And in order not to get confused in the multitude of markings when choosing the necessary product, you should find out the meaning of the English-language abbreviations.
Looking closely at the designations of twisted pairs, it is easy to see that the last two capital letters TP are found in almost all cable names. It's short for Twisted Pair. Translated from in English it stands for "twisted pair". The U in front of Twisted Pair is the abbreviated passive participle Unshielded. It translates as "unprotected". Therefore, any cable with the abbreviation UTP is considered unprotected twisted pair. To put it more clearly, it does not have individual layers of insulation between its twisted pairs.LAN cables in which the copper pairs are insulated from each other are called Shielded Twisted Pair (STP). The group of STP cables includes PiMF (Pairs In Metal Foil) twisted pair marking. Translated, this phrase means "a couple in metal foil." The same type should include LAN cables S/STP, F/STP. The letter S before the slash means Shielded (protected), and F (Foiled) - obstructive, but in this context it is translated as "foil". However, it cannot be argued that the concepts of S/STP and F/STP are almost synonymous. The differences between the two are that the F/STP outer shield is made of aluminum foil, while the overall S/STP shield is made of copper wire braid. It should be noted that , classified in North America(Canada and USA) as ScTP (Screened), also refers to shielded LAN cable types that have an overall aluminum shield.
International classification of information cables
However, there is confusion among manufacturers in LAN cable encodings. And the problem arises when it is required to specify the location of the shielding layer. The latter can be located in two places. Located on top of a separate pair is called individual. Located around isolated pairs ( twisted pair ftp) is called common. To avoid confusion, an international classification of LAN cables has been created. When compiling it, the following were taken into account:
- the presence of a common 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 screen over all twisted conductors. For example, an S/FTP cable differs from an FTP cable in that all twin conductors have a common shield made of a 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 recent years, the abbreviations "TQ" have become increasingly common. They mean that the conductors are not twisted in pairs, but in fours. Returning from the "fours" to twisted pairs, the most tricky question should be clarified. If there is no screen around each individual twisted pair, and protection is located only on top of all twin 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.
STP cable naming features
There is a lot of confusion when choosing the required cable, which has the designation STP. This marking can mean 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 copper twisted pairs.
UTP and FTP cables: main differences
Having a little understanding of the international classification of twisted-pair cables, we should consider the distinctive characteristics of UTP and FTP twisted pairs. In terms of information utp cable 4
, which has neither individual shields for twisted pairs nor a common shield, has another 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 drain wire has no insulation and is connected to a common aluminum screen along its entire length. It is provided in case of a sudden rupture of the aluminum sheath during strong bends or excessive stretching of the cable. In this situation, the drain wire becomes a kind of connecting brace for the screen.
For shielding, FTP cables use aluminum or an aluminum polymer film. The latter is laid with the metal side inward, on the surface of pairwise twisted conductors. As a result 
By adding additional elements, foil coaxial cable (FTP) becomes slightly thicker than unshielded twisted pair (UTP). In addition, the flexibility of FTP is somewhat lower than that of UTP.
Foiled twisted pair cable has an advantage over unprotected twisted pair cable. The first is better protected from high-frequency interference. But for this twisted ftp cable and the case of a computer or other electronic equipment must be grounded in accordance with all the rules. Even worse is the situation with interference at low frequencies. Aluminum screens are not able to prevent low-frequency waves generated by powerful collector motors. For this reason, twisted-pair FTP is not used in industrial production. In addition, foil LAN cables are characterized by low signal attenuation parameters.
Comparing the disadvantages and advantages of protected and unprotected twisted pairs, one should not forget about the price. With a small budget cable utp buy much more profitable, since its cost is much lower than a foil LAN cable.
Statistics show that ftp cable more commonly used in France. And a significant part of the computer networks in the United States and England is equipped on the basis of UTP cables. Residents of Germany prefer twisted-pair cables with two screens: individual for each pair of conductors and a common one. You can buy a twisted pair cable from AVS Electronics.
The meaning of some English abbreviations on LAN cables
When choosing an information cable for your needs, you must carefully read the inscriptions on it. Knowing conventions abbreviations, any buyer can easily pick up the right product. The letter combination LAN itself translates 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 CCA abbreviation, which informs the buyer that in front of him is a cable in which the conductors are made of aluminum and are clad (coated on top) with a layer of copper. In Russian, instead of CCA, the term "composite" is used. 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 those is several times less, however, their 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 categories Cat5, Cat4 and Cat6 are equipped inside with 4 twisted pairs. The letter E after Cat5 indicates that this category is extended. And for the manufacture of twisted pairs of FTP of the Cat5e class, not aluminum, but copper wires are necessarily used. twisted couple utp You can buy from AVS Electronics. Also in the assortment of the company there are various types
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