Twisted pair for network. International classification of information cables

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 clarified that I need 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 approved my candidacy and the bank was ready to give me a loan, the courier was ready to bring everything Required documents only tomorrow, as he already has 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 they receive 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, this application should be processed by one of the managers and appointed a responsible person who will call me back, again clarify whether it is that I want to change the type of payment and then 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!

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

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

Technical differences

Differences in cable specifications are manifested not only in the appearance of the cable; so let's take a look at the possibilities of each category. Below is a table of standards by which you can choose the cable for your case.

Increasing the category number also increases the data rate and frequency at which the cable operates. This is not a coincidence, as each new category places higher demands on crosstalk suppression (XT) and conductor insulation efficiency.

But the table data are not postulates at all. It is physically possible to use a Cat-5 cable for gigabit speed, just as it is possible to make a cable longer than 100 meters. The standard has not been tested in your specific environment, so results may vary. The reverse is also true, if your cable is Cat-6, it does not mean at all that you will have a data transfer rate of 1 Gigabit / second. Network equipment and outlets to which this cable is connected must also support this speed, and there must also be appropriate settings in the network card driver, operating system, etc.

Category 5 has been revised and has been overwhelmingly replaced by Category 5 Enhanced (Cat-5e). Physically, nothing has changed in the cable, only a more stringent standard regarding crosstalk has been applied.

Category 6 has been revised to become Augmented Category 6 (Cat-6a), which has been tested at 500 MHz (compared to 250 MHz for Cat-6). The higher communication frequency eliminated crosstalk (AXT), resulting in higher data rates up to 10 Gb/s over longer distances.

Physical differences

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

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

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

Many Cat-6 cables have a nylon thread that simplifies the cutting of the cable and increases the strength of the cable. Although filament is optional in Cat-5, some manufacturers add it anyway. In Cat-6 cable, filament is also optional as long as the cable passes the tests of the standard. In the picture above, only the Cat-5e cable contains nylon filament.

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

Shielded (STP) or Unshielded (UTP) cable

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

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

Solid or stranded cable

The term solid or stranded cable refers to the actual copper conductors inside the cable. Solid means that the inner conductor is presented as a single piece of copper, and stranded means that several thin copper conductors are twisted together. There are different applications for each type of conductor, but most readers only need to know about two of them.

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

Solid cable (Solid, pictured below) is not as flexible, but more durable, it can be ideally used for permanent networks - both outdoors and indoors.

This is a translation of the article

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. In addition, the LAN cable is also divided into classes and they 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 a twisted-pair cable in a lower class does not support higher-class technical applications. The higher the class, the better the transmission characteristics and the higher 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 high 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.

Main 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. In the case of a capacity of more than 25 pairs, they are divided into bundles of 25 pairs each, the totality of which forms a cable core.
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 trunk 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, including the type, data on the diameter of the conductors and their number, the name of the testing laboratory, as well as foot or meter length marks. The linear 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. 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!

Creation date: 2013-03-09

Twisted pair (twisted pair) - a type of communication cable, is one or more pairs of insulated conductors twisted together

A twisted pair is a type of communication cable. This is one or more pairs of insulated conductors, which are interconnected by twisting, the plastic sheath allows you to protect the wires from external influences and damage. Cables differ in the number of pairs that are present in their structure, hence the different uses of twisted pairs. For example, you can take an Internet connection, for which a UTP cable with 2 or 4 pairs of cores is suitable. As a rule, the conductors are made of copper-plated aluminum or copper. As for telephony of the analog type, twisted pair cable with 3 cores (UTP) or less is enough.

Today, twisted pair is one of the most common types of cables that are used to connect devices and entire communication systems. Video surveillance also could not do without the use of twisted pair. The analog and digital signal is transmitted between devices using UTP 2 and 4 cables.

Interesting! Many are interested in where the name "twisted pair" came from. Everything is simple here - conductors twisted in pairs, isolated from each other, prompted the correct name.

Each twisted pair has its own twist pitch, which is able to provide high performance in low-current signal transmission. True, the UTP cable is not strong in range, high-quality transmission is maintained at a distance of up to 150 meters.

Classification

Twisted pair is primarily split along protection. Twisted pairs are covered with aluminum foil or grounded copper braid. Depending on the coverage, the cable is divided into the following categories:

• 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 outer foil shield;
• protected twisted pair ( STP - Shielded twisted pair) - there is a screen in the form of a braid for each pair;
• foil shielded twisted pair ( S/FTP - Shielded Foiled twisted pair) this cable has a foil protection for each pair, as well as an outer copper braid shield;
• protected shielded twisted pair ( S/STP - Screened shielded twisted pair) - differs from STP by the presence of an additional common external shield made of copper braid;

• SF/UTP (Screened Foiled Unshielded twisted pair- shielded twisted pair with protection) - has two external screens. One is copper mesh and the other is foil screen. There is a drain wire between them.

The next division occurs according to the structure of the conductors. For the manufacture of twisted pair cable, stranded or single-core cable can be used. In the first version, each wire consists of several copper wires, and in the second, respectively, of one.

Typically, a UTP cable includes four twisted pairs - this is the standard for most systems. The conductors used for twisted pairs are made of copper wire with a thickness of 0.5-0.65 millimeters. You can find out the exact thickness by marking, for example, you can take 4x2x0.55 24AWG. It is decoded as follows:

• There are 4 double wires in the cable;
• The cross-sectional diameter of each wire is 0.55 mm;
• Cable gauge is 24 AWG.

As for the abbreviation AWG, it stands for American Wire Gauge, which translates into Russian as American Wire Gauge. In fact, AWG stands for the diameter of the cable section. Keep in mind that a larger gauge will have thinner cables. The table that you can see below shows the correspondence between the diameter of the twisted pair wire and the AWG gauge.

At the moment, several categories of cable are used, they are numbered from CAT1 to CAT7. Each category has a specific frequency range that is passed through the cable. The higher the category, the more pairs of conductors will be in the cable. Also, for a high category, more turns per unit of length are used. The maximum bandwidth to pass is what determines the category of twisted pair. It is determined by the number of turns that fall on one unit of cable length.

• 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) - the old type of cable, 2 pairs of conductors, supported data transfer at speeds up to 4 Mbps. Now sometimes found in telephone networks.
• CAT3(frequency band 16 MHz) - 4-pair cable, used in the construction of local networks, supports data transfer rates up to 10 Mbps or 100 Mbps. Also still found in telephone networks.
• CAT4(frequency band 20 MHz) - the cable consists of 4 twisted pairs, was used in local networks, the data transfer rate does not exceed 16 Mbps per pair, is not used now.
• CAT5(frequency band 100 MHz) - 4-pair cable, used in the construction of 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(frequency band 125 MHz), 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 1 Gbps when using 4 pairs, is the most common network cable. carrier used in computer networks so far
• 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 1 Gb / s. Added to the standard in June 2002. There is a category CAT6a, in which the frequency of the transmitted signal is increased to 500 MHz. It is also used in Gigabit Ethernet networks and supports speeds up to 10 Gb / s at a distance of up to 100 meters.
• 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).

If you want the network cable to last as long as possible, you need to take installation seriously. Do not allow bends and stretching along the entire length of the cable. If the integrity is violated, the screen structure is damaged, as a result, electromagnetic interference and the resistance of the cable to interference are significantly reduced.

Important! International standard cablesUTP is offered with markingx/YZZ where is the first letterX denotes the common screen encoding around all pairs,Y encodes the entire screen around a specific twisted pair,ZZ is responsible for encoding the type of twist. The tables below will help you understand the meaning of these codes, after which you can choose the right twisted pair cables.

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-clad 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.

For outdoor cabling, or near strong EMI sources, it is recommended to use a 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 - in this type, a double braid of the entire cable (without separate shielding of pairs) of foil and copper braid is implemented.

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 wires 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.