Twisted pair (network cable) Definition of twisted pair, types of cables, description of design and categories, crimping schemes, installation. http://www.site/lan/vitaya-para-setevoi-kabel http://www.site/@@site-logo/logo.png

Twisted pair (network cable)

Definition of twisted pair, types of cables, description of design and categories, crimping schemes, installation.

twisted pair (twisted pair) - a type of communication cable, is one or more pairs of insulated conductors twisted together (with a small number of turns per unit length), covered with a plastic sheath. The twisting of conductors is carried out in order to increase the connection of the conductors of one pair (electromagnetic interference equally affects both wires of the pair) and the subsequent reduction of electromagnetic interference from external sources, as well as mutual interference during the transmission of differential signals. To reduce the coupling of individual cable pairs (periodic convergence of conductors of different pairs), in UTP cables of category 5 and above, the wires of the pair are twisted with different pitches. Twisted pair is one of the components of modern structured cabling systems. Used in telecommunications and computer networks as a network carrier in many technologies such as Ethernet, ARCNet and Token ring. Currently, due to its low cost and ease of installation, it is the most common solution for building local networks.

The cable connects to network devices using an 8P8C connector (often erroneously referred to as RJ45 or RJ-45), slightly larger than an RJ11 telephone connector.

Types of cable used in networks

Depending on the presence of protection - electrically grounded copper braid or aluminum foil around twisted pairs, the types of this technology are determined:

• unprotected twisted pair(UTP - Unshielded twisted pair) - there is no protection or shielding;
• foil twisted pair(FTP - Foiled twisted pair) - also known as S / UTP, there is one common external screen;
• protected twisted pair(STP - Shielded twisted pair) - there is a screen for each pair;
• foil shielded twisted pair(S / FTP - Shielded Foiled twisted pair) - differs from FTP in the presence of an additional external shield made of copper braid;
• protected shielded twisted pair(S / STP - Screened shielded twisted pair) - differs from STP in the presence of an additional common external screen.

Shielding provides better protection against electromagnetic interference, both external and internal, etc. The shield is connected along its entire length to an uninsulated drain wire, which consolidates the shield in case of division into sections due to excessive bending or stretching of the cable.

Depending on the structure of the conductors, the cable is used single-core and multi-core. In the first case, each wire consists of one copper core, and in the second - of several.

A single-core cable does not imply direct contacts with connected peripherals. That is, as a rule, it is used for laying in boxes, walls, etc., followed by termination with rosettes. This is due to the fact that copper conductors are quite thick and break quickly with frequent bends. However, for "cutting" into the connectors of the socket panels, such cores are the best suited.

In turn, a stranded cable does not tolerate “cutting” into socket panel connectors (thin cores are cut), but it behaves remarkably when bending and twisting. In addition, stranded wire has greater signal attenuation. Therefore, multi-core cable is mainly used for the manufacture of patch cords ( patch cord) connecting the periphery with sockets.

Cable design

The cable usually consists of four pairs. Conductors in pairs are made of solid copper wire 0.5-0.65 mm thick. In addition to the metric system, the AWG system is used, in which these values ​​​​are 24 or 22, respectively. The thickness of the insulation is about 0.2 mm, the material is usually polyvinyl chloride (English abbreviation PVC), for higher quality samples of category 5 - polypropylene (PP), polyethylene (PE). Particularly high-quality cables are insulated with expanded (cellular) polyethylene, which ensures low dielectric losses, or Teflon, which ensures a high operating temperature range.

Also inside the cable there is a so-called “breaking thread” (usually kapron), which is used to facilitate cutting 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. Also, the tear thread, due to its high tensile strength, performs a protective function.

The outer shell has a thickness of 0.5-0.6 mm and is usually made of the usual polyvinyl chloride with the addition of chalk, which increases fragility. This is necessary for 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 halogens when heated (such cables are labeled as LSZH - Low Smoke Zero Halogen and usually have a bright outer sheath color).

The most common shell color is grey. An orange coloration generally indicates a non-combustible sheath material that allows lines to be laid in enclosed areas. In general, colors do not indicate special properties, but their use makes it easy to distinguish communications with different functional purposes, both during installation and maintenance.

Separately, it is necessary to note the marking. In addition to information about the manufacturer and type of cable, it necessarily includes meter or foot marks.

The shape of the outer shell can also be different. More often than others, the simplest one is used - round. Only for laying under the floor, for obvious reasons, a flat cable is used.

Cables for outdoor laying must have a moisture-resistant polyethylene sheath, which is applied (as a rule) with a second layer over a conventional, PVC one. In addition, it is possible to fill voids in the cable with water-repellent gel and armor with corrugated tape or steel wire.

Cable categories

There are several categories of twisted pair cable, which are numbered from CAT1 to CAT7 and determine the effective frequency range to pass. Higher category cable usually contains more pairs of wires and each pair has more turns per unit length. Categories of unshielded twisted pair are described in the standard EIA/TIA 568(American standard for wiring in commercial buildings).

• CAT1(bandwidth 0.1 MHz) - telephone cable, only one pair (in Russia a cable is used and no twists at all - " noodles"- her characteristics are not worse, but the influence of interference is greater). In the USA it was used earlier, only in a "twisted" form. Used only for voice or data transmission using a modem.
• CAT2(frequency band 1 MHz) - an 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(frequency band 16 MHz) - 4-pair cable, used in the construction of local networks 10BASE-T and token ring, supports data transfer rates up to 10 Mbps or 100 Mbps using 100BASE-T4 technology. 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) - the cable consists of 4 twisted pairs, was used in token ring, 10BASE-T, 100BASE-T4 networks, the data transfer rate does not exceed 16 Mbps over one pair, is not used now.
• CAT5(frequency band 100 MHz) - 4-pair cable, used in the construction of 100BASE-TX local networks and for laying telephone lines, supports data transfer rates up to 100 Mbps when using 2 pairs. When laying new networks, a slightly improved cable is used. CAT5e, this is what is commonly called a twisted pair cable, due to its high transmission speed, up to 100 Mbps when using 2 pairs, and up to 1000 Mbps when using 4 pairs, is the most common network media used in computer networks so far. Restriction on cable length between devices (computer-switch, switch-computer, switch-switch) - 100 m. Restriction hub-hub - 5 m.

Category 7 twisted pair

• CAT6(frequency band 250 MHz) - used in Fast Ethernet and Gigabit Ethernet networks, consists of 4 pairs of conductors and is capable of transmitting data at speeds up to 1000 Mbps. Added to the standard in June 2002. There is a category CAT6a, in which the transmitted signal frequency is increased to 500 MHz. According to the IEEE, 70% of installed networks in 2004 used CAT6 cable.
• CAT7- The specification for this type of cable has not yet been approved, the data transfer rate is up to 100 Gbps, the transmitted signal frequency is up to 600-700 MHz. This category of cable is shielded. The seventh category, strictly speaking, is not UTP, but S / FTP (Screened Fully shielded Twisted Pair).

Each individual twisted pair that is part of a data cable must have a characteristic impedance of 120 ohms, otherwise the shape of the electrical signal will be irreversibly distorted and data transmission will become impossible. The reason for this can be not only poor quality cable, but also the presence of "twists" in the cable and the use of sockets of a lower category than the cable.

Crimping schemes

These twisted-pair crimping diagrams are for Category 5 cable (4 pairs of conductors). Crimped with 8P8C connector.

There are 2 cable crimping schemes: straight cable and crossover (cross-over) cable. The first scheme is used to connect a computer to a switch / hub, the second one is used to connect 2 computers directly and to connect some old models of hubs / switches (uplink port).

EIA/TIA-568A option:

And according to the EIA/TIA-568B standard:

Crossover cable for connecting two network cards directly at a speed of 100 Mbps (Crossover)
10base-T/100base-TX crossover (T568B)
Pin no. - core color - pin no. at the other end of the cable

Crossover cable for connecting two network cards directly at a speed of 1 Gigabit / s (Crossover)
10base-T/100base-TX/1000base-TX/T4 crossover (T568B)
Pin no. - core color - pin no. at the other end of the cable

The white-orange core changes from white-green, orange to green (for a 100-megabit connection); the blue core changes from white-brown, white-blue to brown (for a gigabit connection, for 100 megabits they can be crimped in any order or not crimped at all).

Using a cable that is not crimped according to the standard can lead to the fact that the cable will not work, or there will be a very large percentage of losses (depending on the length of the cable), as well as situations of a complete cable check to determine the purpose of certain pairs.

To check the correct crimping of the cable, in addition to visual control, there are special devices - LAN testers. Such a device consists of a transmitter and a receiver. The transmitter in turn sends a signal to each of the eight cable cores, duplicating this transmission by lighting one of the eight LEDs, and on the receiver connected to the other end of the line, one of the eight LEDs lights up accordingly. If the LEDs on the transmission and reception light up in a row, it means that the cable is crimped without error. More expensive models of LAN testers may have a built-in intercom, a break indicator indicating the distance to the break, etc.

These crimping schemes are suitable for both 100 Mbit and Gigabit connections. When using a 100 megabit connection, only 2 out of 4 pairs are used, namely orange and green. The blue and brown pairs can then be used to connect a second computer over the same cable. Each end of the cable is split into two, two pairs each, and two cables are obtained, as it were, but under one insulation. However, this connection scheme can reduce the speed and quality of information transfer. When using a gigabit connection, 4 pairs of conductors are used.

There are also restrictions on the choice of cross-wiring scheme imposed by the Power-Over-Ethernet (POE) standard, but this standard has not yet been fully approved. With a direct connection of the cores in the cable ("one to one"), this standard will work automatically.

Mounting

When installing a twisted pair cable, the specified curvature at the bends must be maintained. Exceeding may lead to a decrease in the resistance to pickups or to the destruction of the cable.

When installing a shielded twisted pair, it is necessary to monitor the integrity of the shield along the entire length of the cable. Stretching or bending leads to the destruction of the screen, which leads to a decrease in resistance to pickups. The drain wire must be connected to the connector shield.

Document Operations

Despite the intensive development of wireless technologies, cable data transmission lines still remain the most reliable, noise-proof, and relatively inexpensive solution for organizing scalable computer networks with access control. The choice of a twisted pair when designing and laying such networks is one of the main tasks. time with a guaranteed stable connection of its active components will be quite difficult. Moreover, the intensive development of data transmission technologies leads to the fact that equipment operating at a speed of 100 Mbps is gradually being replaced by equipment of 1000 Mbps, respectively, when designing SCS, it is necessary to provide a certain margin of safety, because. the increase in speed implies increased attention to the quality of the lines. Therefore, when choosing a twisted pair cable, you need to consider the following factors:

1. Budget allocated for laying the network (selection of optimal parameters)
2. cable laying conditions(resistance to environmental conditions, rodents, corrosion, electromagnetic radiation)
3. Line length(more distance - higher requirements for cable quality and laying conditions)
4. Transfer rate. For a painless transition to a speed of 1 Gbps in the near future, it is worth paying more attention to the quality of the lines, and buy twisted pair with some margin of safety.

The twisted pair parameters that must be taken into account when designing SCS are as follows:

• Category. According to the standards of telecommunications cable networks EIA / TIA 568, and ISO 11801 there are ten of them: categories 1-4 do not meet modern requirements, and are not currently used, and categories 7 and 7a are inferior in expediency to optical cable. Therefore, we will focus on categories 5, 5e, 6, 6a.
• Core material. Copper or copper plated aluminium. Plus, you should pay attention to the technology of copper plating: CCA, CCAA, CCAG, or CCAH
• Outer shell type: for external or internal laying
• Shield Type: for laying near strong sources of electromagnetic radiation
• The presence of a cable or armor for aerial laying, or laying in a room infested with rodents

The main difference between the categories of twisted pair is the frequency of the transmitted signal, which, in turn, determines the quality and speed of data transmission. Categories 5 and 5e operate in the frequency band up to 100 MHz. Using a category 5e cable, the data transfer rate can be up to 1 Gbit / s, so this category cable is currently the most common for laying computer networks.

Categories 6 and 6a apply to the 250 and 500 MHz signal, respectively. Such a signal allows you to organize data transmission at speeds up to 10 Gb / s over distances up to 50 meters. In the future, it is planned to use it for data transmission at speeds up to 40 Gbps. However, such speed parameters are highly specialized, and the use of the sixth category of cable for laying networks can hardly be called an economically optimal option.

Twisted pair core material

Twisted pair conductors can be copper or copper-plated. The difference, as usual, is in price and quality. The conductivity of copper is higher, but the cable with copper conductors is more expensive. Copper plating of cores is carried out with the expectation of the skin effect. Its essence lies in the fact that at high frequencies of the transmitted signal, most of the current flows through the surface layer of the conductor. However, despite the fact that copper-plated cable has many opponents, few people take into account that copper plating is different, and Hortex aluminum-clad cable can be a good alternative to copper cable. High-quality plating allows you to achieve indicators close to the parameters of a copper conductor. It's all about the production technology and the percentage of copper in the cable conductor. While most twisted pair manufacturers use CCA (copper clad aluminum) technology, cable manufacturer Hortex uses CCAG (Copper Clad Aluminum and Argentum Powder) technology. This technology makes it possible to achieve higher quality copper plating of aluminum compared to CCA, which significantly increases the conductivity of the twisted pair. But the price of such a cable, in comparison with copper counterparts, differs in a pleasant way.

Shielded twisted pair

When running a twisted pair cable near power lines, powerful sources of electromagnetic radiation, or equipment that creates strong electromagnetic interference, factors such as the quality of the insulation and shielding of the cable take on additional importance. As a rule, to prevent interference and signal loss, the network cable is laid no closer than 15 cm from household electrical wiring, however, for each specific case, the distance is determined separately.

When laying the cable outdoors, or near strong EMI sources, it is recommended to use shielded cable. Shielded cable marking is as follows:

• FTP - common foil shield for all pairs in the cable
• STP - each pair is shielded, and the common shield can be made in the form of a metal mesh
• S / FTP - each pair is shielded with foil, plus there is a copper braid for the entire cable.
• SF/UTP - this type implements a double braid of the entire cable (no separate shielding of the pairs) of foil and copper braid.

Features of internal and external laying. Differences in insulation materials.

Having dealt with the various characteristics of a twisted pair, it's time to deal with the most important question - what, where, and how to lay. Which cable to choose for laying a local network.

First of all, you should take into account the temperature regime. Initially, all conscientious twisted pair manufacturers (such as, for example, Larex, Sofetec, and Hortex) use materials for the outer sheath that can withstand significant temperature changes. The most popular material is PVC. In almost all respects, including fire protection, it is suitable for indoor use, but is not suitable for outdoor use. This is due to the fact that PVC, reinforced with plasticizers and various chemical additives, tolerates temperature changes, bending and stretching, but is a moisture-permeable and UV-resistant material. Light-stabilized polyethylene is mainly used for outdoor laying. This material is resistant to temperature changes, moisture-proof, and light stabilization makes it resistant to ultraviolet radiation. The double sheath of cables, Sofetec, and Hortex provides increased strength and resistance to external factors.

For air laying, pay attention to the presence of an additional load-bearing element (cable or wire). It will take on all the loads, and will not allow the cable to break.

When laying a home or small office network, the following requirements must be considered:

• Twisted-pair cables must be laid at a distance of at least 15 cm from household electrical wiring, while minimizing the number and length of sections with parallel arrangement of power and information lines. For storey and interfloor trunk lines with a high concentration of information cables, the ideal option would be to lay power and twisted pair cables along opposite walls. Only in this case, you can give the maximum, but not 100% guarantee that the UTP cable will be completely protected from external EMI.
• The intersection of the wires of the mains, and the twisted pair must be strictly perpendicular.
• If the above requirements cannot be met, for whatever reason, a shielded cable must be used to reduce the impact. In this case, the cable must be grounded on both sides, otherwise, instead of protecting the twisted pair cores from EMI, the shield will become an antenna for interference.

How to choose a quality twisted pair cable

Everything is clear with the parameters and conditions of the external environment. How to choose and buy twisted pair , which will suit the specific conditions of the gasket, and that at the same time it will be of the required quality? The easiest option is to take with you someone who knows what's what. Otherwise, you will have to rely on your own knowledge.

• First of all, make sure you have a certified cable in front of you. Although it is somewhat more expensive than handicraft counterparts, it will last many times longer. And at the same time, you will be sure that you will get exactly what you pay for, because nameless manufacturers save on everything, violating conductor and insulation thickness standards, component quality requirements, etc.
• Pay attention to the material lived. There are two ways to distinguish copper from clad cable:

1. Heat the end of the core in the flame of a lighter. A droplet forms on the copper wire, but at the same time, the core itself is not deformed. Copper-plated aluminum bends at the point of heating, and with strong heating it can break off.
2. Scrape off the top layer of the core. The white sheen of the metal will mean that you have a copper bar in front of you. Type of copper plating (CCA or CCAG, unfortunately, it will not be possible to determine in the field)

• Assess the cable visually and by touch. The insulation must be homogeneous, smooth, without all kinds of roughness and seals, with a uniform color.
• Check core thickness. To do this, you need a micrometer. The thickness of the cable cores is indicated in the cable marking as AWG XX. AWG (from the English American Wire Gauge) is an American wire thickness marking system, and the XX value will determine the thickness of the core. For AWG24 cable, the conductor thickness is 0.511mm, for AWG25 it is 0.455mm.

The result of choosing a low-quality or non-standard cable is only one: signal loss, and, as a result, unstable network operation. If the cores are thinner than standard, then the contact in the module (network connector) may be completely absent. Poor-quality insulation can crack and/or crumble, and if the cable is laid outside the building, then water will get under the insulation, which may sooner or later end up in network equipment. If the cable is laid indoors, then the destruction of the insulation will make the cable more vulnerable to mechanical damage. Poor copper plating reduces the conductive properties of the conductors.

In order to be sure of the quality of the cable, we recommend that you pay attention to the trademarks Larex, Sofetec And Hortex. The core strictly complies with the thickness standard, double sheath, high-quality cladding: all this distinguishes these brands from products of other manufacturers. Despite the fact that Larex and Sofetec are clad using CCA technology, and the parameters of this cable are somewhat lower compared to copper, if the standards and requirements for cable laying are observed, the properties of the cable of these brands will provide a sufficient margin of safety and reliability of the SCS. The Hortex cable, clad according to CCAG technology with a high percentage of copper, in turn, is the closest in its electrical parameters to copper cables and has a core resistance of ≈140 Ohm/km. Also, cables of brands Larex, Sofetec and Hortex have all the necessary certificates and compliance with quality standards and fire safety.

Features and specifics of choosing a cable for solving different problems

The main requirements set by the SCS designer come down to stable operation of the network, minimization of losses, and the maximum line of network service. The tasks, the solution of which requires the fulfillment of the above requirements, are different. For the most typical projects of small office or home networks, subject to the laying rules, it will be enough buy twisted pair UTP cable both when laying to the router, and from the router to the computer. For larger office networks, UTP is also preferable because shielded cable introduces additional shield grounding difficulties: ANSI/TIA/EIA-568-A and international standard ISO/IEC 11801 require the shield to be grounded at both ends on the bus telecommunications grounding system. Due to the difficulties of grounding, FTP is recommended when laying inter-server, intra-cluster lines within the common contour of the information "ground", or within different contours, but with the fulfillment of all requirements for the ground contours of information circuits.

Twisted pair is also used to create video surveillance systems. It carries a video signal and it is recommended to use a shielded cable, especially if the video equipment is powered remotely.

Regardless of the types of tasks, and the requirements placed on the cable, first of all, it must comply with standards and have quality certificates, which guarantees its performance in any segments of structured networks and network protocols. Therefore, if the budget does not allow the use of a copper cable, you should not use products from nameless manufacturers. Despite the fact that the cost of such a cable is significantly lower, the savings will be doubtful if the cable has to be completely changed after a year. Cables of Larex, Sofetec and Hortex brands allow you to optimize the budget for laying cable lines, and guarantee high quality products, which allows you to use the cable to solve a wide range of problems.

This won't halt the execution of your script, but as long as setTimeout() is an asynchronous function, this code

Console.log("HELLO"); setTimeout(function()( console. log("THIS IS"); ), 2000); console log("ME"); will print this in the console:
HELLO ME THIS IS *(note that ME is printed before THIS IS)
function sleep(ms) ( ms += new Date().getTime(); while (new Date()< ms) { } } now, if you want to sleep for 3 seconds, just use:
sleep(3000); example: http://jsfiddle.net/forgery/8t0neran/

Please note that this code will keep your script busy for n milliseconds. This will not only stop execution of Javascript on your page, but depending on the browser implementation, may possibly make the page completely unresponsive, and possibly make the entire browser unresponsive . In other words, this is almost always the wrong thing to do.
If you do sleep more than 10 seconds, browser shows alert: "A script on this page may be busy, or it may have stopped responding. You can stop the script now, open the script in the debugger, or let the script continue."

Friday, 15 May 2015

Wednesday, 17 December 2014

This is the second time I've come across this store and the utter stupidity of the staff, and the second time I say to myself: "Enough!". I really hope this time will be the last.

Decided to buy a gift for my wife for the holidays. Assuming possible problems, based on previous negative experience, I began to negotiate in advance. So...

Day 1 (Tuesday, November 25)

I went to the store's website, chose the phone I was interested in and pressed the "Buy in 1 click" button, entered my phone number and waited for a call back.

An hour passed, then another, and no one called me ...

Then I dialed their number from my mobile. The phone was picked up by the operator, who asked for information about me, specified what I wanted to buy and recommended additional accessories, with which I agreed. We agreed that I would apply for a loan through a bank, namely Alfa-Bank JSC. The request to the bank should have been transferred after they asked me for a bunch of more information. I specified that I needed the order not just like that, but by a specific date, and since it is issued as a loan, I ask you to bring it early, without waiting for approval from the bank, or reduce this period to a minimum.

Day 2 (Wednesday, November 26)

The next day, when I did not wait to receive a message about the order made - neither an SMS to the specified number, nor a letter to the specified mailbox, I had to call back again.

Naturally, it turned out that the bad person who placed my order yesterday either didn’t save it, or something else, but they didn’t find it. No, the operator, of course, said that everything was OK, but I just needed to clarify my data and for the second time arranged for me to poll all my data. At the end, she promised that everything would be fine.

Within half an hour I received an SMS notification that my order was placed.

Day 3 (Thursday, November 27)

The next day, not allowing the situation to take its course, I called the operator back to clarify when a representative of Alfa-Bank would contact me. It turned out that the operator did not know what and when it would be and gave me the phone number of the bank where I should call to find out this information.

Naturally, it turned out that this is just some number, and not a number where they can provide this information (well, at least the right bank). However, they still helped by giving the number of the credit department of their bank. When I called back, I found out that the data on my request had not been received.

I had to call back the Allo store operator, due to whose confusion, as well as some questions asked again, I realized that they simply did not send the application to the bank. Then followed the next assurances that everything will be fine.

Day 4 (Friday, November 28)

During the day, I called the bank and the store several times to find out about the status of my loan application. It's done! On the evening of the 4th day, my loan application was delivered to the bank. And then real Hell began, they asked me so much information - that I didn’t even know that there could be so much of it ... about me, relatives, work and my friends (well, at least they didn’t ask about my friends).

But they can come to me and apply for a loan only next week after this application is transferred to the responsible person in the bank.

So I did not manage to arrange everything I needed in one week.

Day 7 (Monday, December 1st)

From the very morning I began to call the bank to somehow force a loan. But it turned out that this responsible person should call me back as soon as he gets to the application, as he has some more questions.

At lunchtime, a bank employee called me back, clarified all the information again and told me about the terms of the loan. It turned out that I would have to pay a one-time loan insurance in the amount of 1% of the issued loan, while the accrual of interest on the loan would be 2% and would be accrued from the second month. For my case, it was ideal, since I needed a loan for a week (only to borrow the goods until the money arrived in my account). This worker said that he would send it to the credit commission for consideration.

Maximum, consideration by the credit commission is carried out in 8 hours, at the end of the consideration, the commission either approves the issuance of a loan, or refuses, but in any case, one more day burned out.

Day 8 (Tuesday, December 2)

In the morning, at 10 o’clock, they called me and said that the loan commission had approved my candidacy and the bank was ready to give me a loan, the courier was ready to bring all the necessary documents only tomorrow, since he already had everything scheduled for today. I once again reminded that I would need to do it as quickly as possible, since the store will not deliver the goods until it receives confirmation from the bank, which they will not be able to give until I sign the contract. Thus, after signing the contract tomorrow, they will be able to give an answer to the store and, at best, the store will send a request to move goods from another city only then, plus at least a day to move, and it will be good if I can get it this week, although all this mess brewed at the beginning of the last. To which in response I received a firm "NO", that it is impossible to speed up all this in any way.

After I agreed with all this, I was once again read out the list of my goods and the amount of payments from my side. BUT, the amount has already changed. It turned out that now I do not have to pay 1% as insurance compensation for loans, but about 8%. In response to my indignation, I was informed that I misunderstood the last time (unfortunately I did not think of recording a phone call earlier).

Naturally, such an overpayment did not suit me at all, so I refused the services of the bank, and since the deadline for the appearance of money in my account had already approached for all the time of this red tape, I decided to call the store and change the payment from a loan to cash. Which I did as quickly as possible. I tried to express my indignation at the impudence of the bank, but they were not accepted, saying that they could not influence the bank in any way - there is what it is.

I asked for the transfer to be done as soon as possible, since I am already ready to pay cash, and as soon as the goods are moved, I will take it. Surprisingly, it turned out that all the goods (here we quickly checked the list) have already been moved to Kyiv and are waiting for me. I asked to be moved to a store on Petrovka.

After that, as always, I was assured that everything was OK, and with that we said goodbye.

Day 9 (Wednesday, December 3)

Not expecting a dirty trick, I made the first call in the late afternoon to clarify whether my goods had been delivered to the store I specified. This is where the PROBLEMS began, yes, just like that in capital letters.

At first, they didn’t find me at all, after which they said that yes, my order was there, but it was issued on credit, and therefore there was no delivery to the store.

After that, I once again asked to change the type of payment, to which they said that everything was OK and they would contact me as soon as the goods were delivered to the store.

In the evening, he told his wife that she could call in tomorrow to pick up the goods in the store, only it would be necessary to agree on the time.

Day 10 (Thursday, December 4)

The problems started from the very beginning, when the wife called the store back in the afternoon, it turned out that there was no product there.

My wife called me, and I called the store again, it turned out that again they didn’t change the type of payment, but after not very long conversations and a lot of indignation on my part, I found out a strange situation: they do not have the opportunity to change the type of payment themselves, but only create application for a change, one of the managers should process this application and appoint a responsible person who will call me back, again clarify whether it is that I want to change the type of payment and after that make the change. At first, finding out this state of affairs puzzled me ... and only a little ahead of time, realizing this, I began to find out if they would call me back, and how long all this could go on.

They assured me that this time they would call back for sure, I agreed, but warned that I would call them every hour if they did not call back.

Called back within half an hour. BUT, it turned out that such a product is no longer available, so my application was closed altogether. No objections were accepted.

I called the store back to the support service again trying to restore justice, but it turned out to be beyond my power. The promotion ended, the goods ended, the reservation of the goods for me was only for payment on a loan, and I didn’t find out where the goods had gone, which had just been before the change in the form of payment.

Outcome

I learned how to file a complaint, filed it and that was it. So until now, no one has contacted me from the store and explained where the goods disappeared, which was registered under me and even delivered to the store.

After that, I went to another store, bought the goods and no problems.

If you want problems, use the services of the Allo store!

Undoubtedly, one of the greatest human inventions in the field of transmission of low-current high-frequency signals is the so-called “twisted pair” cable (from the English “twisted pair”).

The essence of this cable is that the signal in it is transmitted using one or more pairs of insulated conductors twisted together with a small number of turns per unit length.

This type of cable, due to its design, allows to increase the degree of connection between the conductors of each pair, and also, due to the synchronization of the influence of electromagnetic interference on both conductors of each pair, to reduce the influence of external interference on the signal as a whole.

The scope of this type of cable is very wide. These include modern structured cabling systems, computer networks, telecommunications equipment, and telephony.

Marking of various types of twisted pair.

First, let's define terminology.

Consider the typical name of a twisted-pair cable (in its full version, of course).

UTP 4 CAT5E 24 CCA

Let's break it down into its components.

UTP- cable type designation. Main types:

UTP - Unshielded Twisted Pair.

FTP - shielded twisted pair.

SFTP is double shielded twisted pair.

4 - in this record denotes the number of pairs.

The standard quantities are 2 and 4 (two-pair and four-pair cable, respectively), however, there are other quantities - 10, 15, 20, 25, etc. - these are the so-called "multi-pair" cables, which are used mainly when installing large SCS.

In this case, the fifth, extra. At the moment, category 5 is the most common and frequently used type of twisted pair category, but it should be remembered that there are lower categories, which are now almost universally replaced by the fifth. And also about the fact that there is a 6th category - which differs from the 5th in that in it each pair, in addition to a different twist pitch, is also separated from each other by a special plastic cross.

The distribution of the nominal 5th category of cable is due to the fact that this was the first category in which a different twist pitch was used for different pairs, which means even greater noise immunity.

24 is a number that characterizes the thickness of the conductor core. For details, see below in the section "Cable construction"

CCA- the material from which the conductor is made. Usually it is copper (Cu, or there is simply no marking, or copper-plated aluminum or steel - CCA).

CABLE CONSTRUCTION

A twisted pair cable consists of several twisted pairs. The conductors in pairs are made of solid copper (or copper-plated aluminum or steel in the case of CCA) with a diameter of 0.4-0.6 mm. The American AWG system is also used to measure the diameters of conductors, in which these conductors are designated 26AWG or 22AWG, respectively.

Standard four-pair cables use mostly 0.51mm (24AWG) conductors.

The insulation usually has a thickness of about 0.2 mm and is made of polyvinyl chloride (PVC), or for higher quality conductors of the 5th category and above - polypropylene (PP), polyethylene (PE). Particularly high-quality conductors are insulated with foamed polyethylene, which allows for lower dielectric losses, or Teflon, which provides a wide operating temperature range.

There is also a so-called “breaking thread” inside the cable (capron is usually used). It allows easy removal of the outer sheath of the cable and, thanks to its high strength, provides additional strength to the cable.

The outer sheath of standard four-pair cables has a thickness of about 0.5-0.9 mm (depending on the category and quality of the cable) and is made of polyvinyl chloride with the addition of chalk to provide some fragility and allow the sheath to be accurately separated at the cut point with a cutting tool. In addition, for the manufacture of the sheath, polymers are used that do not support combustion and do not emit halogens when heated (such cables are marked LSZH - Low Smoke Zero Halogen).

MAIN CABLE TYPES

UTP 2 CAT 5E 24 AWG, UTP 2 CAT 5E 24 AWG CCA- cable type "twisted pair", unshielded, two-pair, standard conductor thickness. Made of copper or copper-plated aluminum or steel (CCA).

It is used when connecting computers within a local network, for laying telecommunications. Due to the fact that it consists of only 2 pairs, when transferring data within the network, it provides speeds up to 100 Mbps.

UTP 4 CAT 5E 24 AWG, UTP 4 CAT 5E 24 AWG CCA- cable type "twisted pair", unshielded, four-pair, standard conductor thickness. Made of copper or copper-plated aluminum or steel (CCA).

It is used to connect computers within a local network, for laying telecommunications, in distributed telephone networks.

Thanks to the simultaneous use of four pairs, it allows you to develop an information transfer rate of up to 1 Gbit / s (1000 Mbit / s).

FTP 2 CAT 5E 24 AWG, FTP 2 CAT 5E 24 AWG CCA- cable type "twisted pair", shielded, two-pair, standard conductor thickness. The conductors are made of copper or copper-clad aluminum or steel (CCA).

When laying communication computer and network routes, specialized cable systems of various modifications are used, which do not differ much from each other in appearance at first glance. In fact, today a huge number of cables of various modifications are produced, the differences of which for an experienced user are very obvious, and the markings on the wires say a lot. Each of the systems, no matter whether it is utp wires or twisted pair from the ftp series, has technical characteristics, operates under certain conditions and differs in performance.

When laying a home or office network system, there is no particular need to select a suitable cable, since the distances of the routes are small enough that this will not significantly affect the performance of the network connection. Therefore, it makes no difference whether utp or ftp wires are used, in general, the system will work stably and quite functionally.

utp cable: main features

Most often, UTP cable is used to create small network routes. This type of cable system is designed in accordance with the international quality and reliability standard ISO 11801, and is produced in accordance with strict adherence to GOST RF.

The cores are intertwined with each other at a certain angle and in a certain sequence in pairs, thereby creating a connection of the best quality, protecting the communication system from external interference. This technology is called twisted pair.

On a note. The quality of the signal is affected by the correct installation - the bending of the wires should not exceed the radius of 8 cable diameters. In the production of UTP cable, this technology is used.

To answer the question what isutpcable, it is worth considering the decoding of its abbreviation:

• U - lack of insulation;
• TP - twisted pair.

The utp cable - translated from English as "Unshielded Twisted Pair", is one or more twisted pairs, between which there is no individual isolation. Depending on the type, it is applicable for both computer and telephone lines. The absence of an insulating coating between the pairs contributes to less resistance to external interference, respectively, the signal quality may deteriorate. Although when laying small communication systems, this factor is not of great importance.

Varieties of yutype cable are characterized by the presence of a number that indicates the number of twisted pairs. In addition, twisted pairs are distinguished, consisting of a single-core cast conductor with a diameter of not more than 0.51 mm (used in installation work in specialized boxes and channels) and stranded (used in places of possible bending). To work with different types of twisted pairs, special equipment is used - connectors, which ensure reliable connections and exclude damage to wires during installation.

Types of utp cables

Networked communications systems are at their peak today, enabling year after year to produce high quality products with a faster rate of performance. Today it is possible to select a cableutpseveral categories:

• Cat1;
• cat2;
• cat3;
• cat4;
• cat5;
• cat5e;
• cat6;
• cat6a;
• Cat7.

Depending on the category, the data transfer rate of the utp system can reach about 50,000 Mbps, with a frequency of up to 700 MHz and extend over a distance of more than 50 meters. At the moment, the utp cable with 2 twisted pairs of Cat5e category is the most popular. In this category, there is the best value for money, as well as data transfer speeds.

In addition, 2 types of utp cable are distinguished by shape: flat and rounded. The shell is made on the basis of polyvinyl chloride with the addition of a small consistency of chalk, which gives it elasticity and facilitates the process of working with it. Between the twisted pairs there is a nylon thread, the main properties of which are to give strength to the wire and protect the twisted pairs from mechanical damage. If you pull on this thread, it will separate one conductor from another in a twisted pair.

To answer what a utp cable is and what its scope is, it is enough to carefully study the inscriptions on the shell, as well as know its color value.

Every meter, markings are applied to the cable sheath indicating the footage. Depending on the country of manufacture, the footage can be indicated both in meters and in pounds. In addition, the main technical characteristics and type of wire, as well as the manufacturer's data, are indicated.

Color coding indicates the area of ​​application. Usually, the following color scheme of the shell can be distinguished:

• The black shell is suitable for outdoor use as it has protective properties that are resistant to the environment;
• Colored sheath (grey, blue, purple, yellow, red, green) suitable for indoor installation only;
• The orange sheath is available in 2 categories for indoor and outdoor installation. In the production of this type of cable, an additional polymer is used, which has non-combustible properties and can withstand temperatures up to 75 degrees.

Difference between ftp and utp wire

The twisted-pair system improves signal quality, twisting the wires in a certain sequence and at a straightened angle protects against external interference, but sometimes this is not enough. This is especially true when laying industrial network routes of great length. To improve the data transfer speed, another type is used - an ftp cable.

Between the utp ftp cable, the difference is that ftp has a special protective screen, which is more resistant to the negative effects of external noise. In this case, each conductor separately, as well as the entire twisted pair as a whole, can be subject to shielding. To maximize performance, all installation should be done correctly, while remembering to ground all computer equipment.

Abbreviationftp stands for the following:

• F - the presence of insulation on each core or twisted pair based on copper, aluminum foil or tape based on a special metal;
• TP - twisted pair.

The marking of network cables can be different, an additional letter can be added to the main abbreviation, for example, S. It means the presence of a common metal braid insulation.

The main types of cable shielding can be distinguished:

• UTP - unshielded twisted pair;
• FTP – foil shielded twisted pair cable;
• STP - twisted pair with common insulation;
• S / FTP - each twisted pair has its own protective foil screen and a common additional copper sheath;
• U / FTP - the presence of a common shielded shell;
• U / STP - the presence of a screen only on each twisted pair.

The shield of the ftp series wire has not only a protective factor against the effects of other electromagnetic fields, but also protects against electromagnetic radiation, which the cable itself emits during operation.