Cables used for lining upComputer network infrastructures are available in a wide range of varieties. Coaxial, twisted pair, as well as fiber optics are among the most popular. What is the specificity of each of them? What are the features of mounting the most common - twisted pair?
Cable types: coaxial
Among the most historically early cable types,used in network connections, - coax. In terms of thickness, it roughly corresponds to a network power cable for a computer, designed to work with a 220 V socket.
The structure of the coaxial structure is as follows:In the middle there is a metal conductor, it is shrouded in thick, mostly plastic insulation. Over it - a braid from copper or aluminum. The outer layer is an insulating sheath.
Connecting a network cable of this type can be done by:
- BNC-connector;
- BNC-terminator;
- BNC-T-connector;
- BNC-barrel connector.
Consider their specifics in more detail.
BNC connector assumes placement at the endscable, used to connect to T-or barrel connector. The BNC terminator is used as an isolation barrier that prevents the signal from moving along the cable. Proper functioning of the network without this element in some cases is not feasible. Connection via a coaxial-type power cable involves the use of two terminators, one of which requires grounding. BNC-T-connector is used to connect the PC to the main line. In its structure there are three slots. The first connects to the network card connector of the computer, and the other two connect the different ends of the trunk. Another type of coax cable connector is the BNC barrel. It is used to connect different ends of a trunk, or to increase the radius of a computer network.
Among the useful features of coaxialstructures - there are no problems with the decision of how to connect two network cables of this type. Enough to ensure reliable contact conductive cores, of course, subject to the technology of coupling the insulation and screen mesh. However, coaxial cable is quite sensitive to electromagnetic interference. Therefore, in the practice of building computer networks, it is now rarely used. However, it is indispensable in terms of the organization of the infrastructure for the transmission of television signals - from plates or cable providers.
Twisted pair
Самые, вероятно, распространенные сегодня сетевые computer cables are called "twisted pair". Why such a name? The fact is that in the structure of the cable of this type there are pairwise conductors. They are made of copper. The standard cable of this type includes 8 cores (in total, thus 4 pairs), but there are also samples with four conductors. The so-called pinout of the network cable of this type (the correlation of each core with a particular function) involves the use of insulation of a certain color on each conductor.
Twisted pair outer insulation is made fromPVC, which provides sufficient protection of conductive elements from electromagnetic interference. There are shielded cables of this type - FTP and STP. In the first, the corresponding foil is located on top of all the conductors, in the second, on each of the conductors. There is an unshielded modification of a twisted pair - UTP. Cables with foil are usually more expensive. But it makes sense to use them only if there is a need for high-quality data transmission over a relatively large distance. For home networks, an unshielded twisted pair is suitable.
There are several classes of the appropriate type.structures, each of them is designated as CAT with a number from 1 to 7. The higher the corresponding indicator, the better the materials that provide signal transmission. Modern network cables for a computer to exchange data over an Ethernet protocol in home networks imply that the elements are CAT5 compliant. In connections where twisted pair is used, connectors are used, which will correctly be classified as 8P8C, but there is also an unofficial name for them - RJ-45. It can be noted that cables that meet at least CAT5 and CAT6 classes can transmit data at speeds close to the maximum for the type of structures under consideration - up to 1 Gbit / s.
Optical fiber
Perhaps the most modern and fast networkcomputer cables are fiber optic. In their structure there are light-conducting elements of glass, which are protected by durable plastic insulation. Among the key advantages that these network cables have for a computer are high immunity to interference. It is also possible to transmit data over a distance of about 100 km through optical fiber. Connecting cables of this type with devices can be carried out through various types of connectors. Among the most common are SC, FC, F-3000.
What does this high-tech network cable for a computer look like? Photos of fiber optic construction below.
Intensity of practical applicationfiber is limited by the relatively high cost of the equipment required to transfer data through it. Recently, however, many Russian providers are actively using this network cable for the Internet. According to IT experts, with the expectation that the corresponding investment will pay off in the future.
The evolution of cable infrastructure
Using the example of the three marked cable types, we canto trace some evolution in the aspect of building the infrastructure of computer networks. So, initially coaxial structures were used when transmitting data via the Ethernet standard. At the same time, the maximum distance to which a signal could be sent from one device to another did not exceed 500 meters. The maximum data transfer rate over a coaxial cable was about 10 Mbit / s. The use of twisted pair has significantly increased the dynamics of file sharing in computer networks - up to 1 Gbit / s. It also became possible to transmit data in duplex mode (one device could both receive signals and send them). With the advent of fiber, the IT industry was able to transfer files at a speed of 30-40 Gbit / s and more. Largely due to this technology, computer networks successfully connect countries and continents.
Of course, when working with a PC, manyother types of cables used in the installation of computer networks. Theoretically, for similar purposes, you can use, for example, a USB cable, although this will not be very efficient, in particular, due to the fact that within the USB standard, data can be transferred for a short distance - about 20 m
How to connect a twisted pair
Twisted pair, as we noted above, is the mostcommon in the design of computer networks type of cable. However, its practical use is characterized by some nuances. In particular, they reflect such an aspect as pinout of the network cable, which we said above. It is important to know how to properly position the wires in the area of their contact with the RJ-45 connector. The procedure by which the twisted pair cable is connected to the corresponding element is called crimping, since during its implementation a special tool is used that implies a force effect on the structure.
Nuances crimp
During this procedure, the connectors are securelyfixed at the ends of a twisted pair. The number of contacts in them corresponds to the number of wires - in both cases, there are 8 such elements. There are several schemes in which the twisted pair can be crimped.
Next we look at the relevant specifics.But first, the person who works with the cable needs to properly take the connectors in hand. They should be held so that the metal contacts are located on top.
The plastic latch should be aimed atthe side of the one who crimps. On the left in this case will be the 1st contact, on the right - the 8th. Numbering is an extremely important nuance of working with twisted pair. So, what kind of crimping is used by network infrastructure specialists?
Firstly, there is a network cable scheme, called EIA / TIA-568A. It assumes the location of the cores relative to the metal contacts of the connector in the following order:
- for 1 contact: white-green;
- for the 2nd: green;
- for the 3rd: white and orange;
- for the 4th: blue;
- for the 5th: white and blue;
- for the 6th: orange;
- for the 7th: white and brown;
- for the 8th: brown.
There is another scheme - EIA / TIA-568B. It assumes the location lived in the following order:
- for 1 contact: white and orange;
- for the 2nd: orange;
- for the 3rd: white-green;
- for the 4th: blue;
- for the 5th: white and blue;
- for the 6th: green;
- for the 7th: white and brown;
- for the 8th: brown.
How to connect a network cable with a connector, you now know. But it is useful to study the specifics relating to the various schemes of connecting the twisted pair to one or another device.
Crimp and connection type
So, when connecting a PC to a router orThe switch should use the direct connection method. If there is a need to organize the exchange of files between two computers without using a router, then you can use the cross connection method. The difference between the marked schemes is small. With the direct connection method, the cable must be crimped using the same pinout. When cross one end - according to the scheme 568A, the other - on 568B.
High tech savings
Витая пара характеризуется одной интересной feature. With a direct connection scheme, the device can use not 4 pairs of conductors, but 2. That is, it is permissible to connect 2 computers to the network simultaneously using a single cable. Thus, you can save on the cable or make a connection, if it really needs to be done, and there are no extra twisted-pair meters at hand. However, in this case, the maximum data rate will not be 1 Gbit / s, but 10 times less. But for the organization of the home network is in most situations acceptable.
How in this case to distribute the conductors? With respect to the pins on the connectors for connecting the first computer:
- 1 contact: white-orange lived;
- 2nd: orange;
- 3rd: white and green;
- 6th: green.
That is, 4, 5, 7 and 8 cores are not used with this scheme. In turn, on the connectors for the second computer:
- 1 contact: white-brown core;
- 2nd: brown;
- 3rd: white and blue;
- 6th: blue.
Можно отметить, что при реализации перекрестной Connection diagrams must always use all 8 conductors in a twisted pair. Also, if the user needs to implement data transfer between devices at a speed of 1 Gbit / s, the pinout will need to be carried out according to a special scheme. Consider its features.
Cross connect at gigabit speed
The first cable connector should be crimped in accordance with scheme 568B. The second involves the following mapping of cores and pins on the connector:
- 1 contact: white and green vein;
- 2nd: green;
- 3rd: white and orange;
- 4th: white and brown;
- 5th: brown;
- 6th: orange;
- 7th: blue;
- 8th: white and blue.
The circuit is quite similar to 568A, but the position of the blue and brown pairs of conductors is changed.
Compliance with the marked rules of color correlationThe cores and contacts on the 8P8C connector are the most important factor in ensuring the functionality of the network infrastructure. The person designing it needs to be attentive when installing the relevant elements. It happens that the computer does not see the network cable - it is often connected just with incorrect crimping of the twisted pair.
How to crimp the cable
Consider some technical details.The main device, which in this case is involved, is the crimper. It is similar to ticks, but it is adapted to work with computer cables of the appropriate type.
The design of the crimper requiresspecial knives designed to cut the structure. Also, sometimes crimpers are equipped with a small device for stripping twisted pair insulation. In the central part of the instrument there are special sockets adapted to the thickness of the cable structure.
The optimal algorithm of actions of a person crimping a twisted pair can be as follows.
- First of all, it is necessary to cut off a section of cable of suitable length - thus, its exact measurements will be required.
- After that, the outer insulation should be removed - approximately in the area of 3 cm at the end of the cable. The main thing is not to accidentally damage the insulation of the cores.
- Then you need to arrange the conductors relative towith the above connection diagrams to the connector. After trimming the ends of the wires, so that the length of each of them outside the outer layer of insulation was about 12 mm.
- Next you need to put the connector on the cable so thatthe conductors remained in the order that corresponds to the wiring diagram, and each of them entered the desired channel. You should move the wires until you feel the resistance of the plastic wall of the connector.
- After appropriate accommodation lived insideconnector PVC sheath should be located inside the connector housing. If this is not done, perhaps you should pull out the wires and shorten them a little.
Once all the structural elements are positioned correctly, you can crimp the cable by inserting the connector into a special socket on the crimper and gently pressing the tool handle until it stops.
