I often have a friend asking me some questions about the network cable, and I found that there is a universality of the network cable, the root source is that the people don't understand the principle, so I think it is necessary to write something. I will talk. First, the difference is transmitted. The so-called differential manner is transmitted, that is, the transmitting end is opposite the electrical signal opposite the phase of the two signal lines, and the receiving end is subtracted to subtract the two line signals, which obtains a signal of the magnitude. The principle of its anti-interference is: If the two signal lines are subject to the same (in phase, equal) interference signal, due to the subtraction of the two lines accepted on the receiving end, the interference signal is basically offset, so how Can you guarantee that the interference signals from the two signal lines are as co-phases, isometric? One of the ways to turn the two lines together, analyze the principle of electromagnetic: It is possible to approximate the interference signal from the two signal lines, etc., etc. After two lines, they will prevent themselves from interfering with others. Generally commonly used is twisted pair. Most local area networks use non-shielded twisted pair (UNP-UNSHIELDED PAIR) to network, and the network cable consists of a long twisted pair with RJ45. The twisted pair is divided into four different colors of the line together to the twisted, the formation of the team is to reduce the effects of electromagnetic radiation and external electromagnetic interference, the twisted pair can be applied to the metal mesh The shield is distinguished into shielded twisted pair (STP) and non-shielded twisted pair (UTP). In the EIA / TIA-568A standard, the twisted pair is distinguished by electrical characteristics: three types, four categories, five types. The most commonly used network is three types of lines and five types, super five categories, there are currently six categories. The third type of twisted pair is often used as data from 10Mbps Ethernet in LAN, which is in line with the standard of IEEE802.3 10BASE-T. The fifth type twisted pair currently has the largest LAN market, with a maximum rate of 100 Mbps, which is in line with the standard of IEEE802.3 100Base-T. Do a good job to connect the RJ45 crystal head to the RJ45 socket of network devices such as NIC or HUB. The corresponding RJ45 plug seat is also distinguished into three or five types of electrical properties. The RJ45 crystal head is composed of metal sheets and plastic, and it is important to note that the pin serial number is 1-8 when the metal sheet faces us, which is very important when the serial number is connected to the network. Mistaken. The maximum transmission distance of the twisted pair is 100 meters. Two twisted lines 568b and 568a are specified in the wiring standard of EIA / TIA. Standard 568B: Orange - 1, Orange - 2, Green White - 3, Blue - 4, Blue White - 5, Green - 6, Brown - 7, Brown - 8 (Figure 2 ) Standard 568A: Green White - 1, Green - 2, Orange - 3, Blue - 4, Blue White - 5, Orange - 6, Brown - 7, Brown - 8 (Figure 3) What is the difference between 568a and 568b? The latter is the upgrade and improvement of the former, but the latter is still in the draft stage, including the definition of permanent links and the six types of standards. In addition, in the construction of the integrated wiring, there are two different lines of wires, and there is no impact on performance in two ways, but it must be emphasized in one project that can only be used. As for the difference between 5 and over 5, the difference is different from the application. The 5-type system is only used in the use of two pairs of cables, which uses half-duplex, and the super five types in order to meet the application of Gigabit Ethernet, using four pairs of full-duplex transmission. Therefore, the distal crosstalk (FEXT), the retransmission loss (RL), the integrated proximal crosstalk (PSNext), integrated ACR, and transmission delays have also become parameters that must be considered. So super 5 categories have higher performance requirements than 5.
The difference between the six and 5 types is that their bandwidth is different, and only 100MHz of the 5 categories is 250MHz. The applications they support are also different depending on performance, and the 6 supports higher levels of applications. There is a higher requirements than the 5 classes in performance, in order to improve performance, in structured 6-class compared to the 5th classes, the identification method of the eight pins of some RJ45 connections is to face themselves, head towards you. From the top to the lower number, it is 1, 2, 3, 4, 5, 6, 7, 8 to apply a wiring method throughout the network wiring, but both ends have the network link between the RJ-45, whether it is 568A, or 568b, is common in the network. The local 1, 2 two feet in the two-way mode are signal transmit terminals, 3, 6 two feets are signal receiving ends, so this two pair of signals must be transmitted using a pair of twisted pairs. Pay special attention to the line. Now 100M network usually use 568B mode, 1, 2 two boats using orange-pair, of which white orange lines are 1 foot, orange line pick 2 feet; 3, 6 two feet use green pair, where the white-green line Pick up 3 feet, the green line is connected to 6 feet, the remaining two pairs are generally not available in 10m, 100M fast Ethernet, usually use a pair of twisted pairs directly from the two joints of the two connections. Even, 4, 5 is blue, 4 is blue, 5 is white blue; 7,8 with brown line, 7 is white brown, 8 is brown. Figure 2. If the network cable is made in a way, it is called a straight cable or straight line. If the two heads of the network cable are not in one way, one is 568B, the other is 568A, then this kind of practice is called cross-cutting, in fact, only one of the heads is 1, 2 and 3, 6 on the basis of 568b. , As shown in Figure 3. Different practices are used in different environments and will be discussed later. The method of making the twisted pair in several applications is described below. The positive line: is the 568B standard anti-line: one is 568B, and the other is 568A. PC: Hub: Hub: Hubo; Switch: Switch; Router: Router PC-PC: Anti-line PC-HUB: Normal Line PC-Switch: Positive Line Hub-Hub General Port: Anti-line HUB-HUB Level Connection: Positive line HUB-HUB level connection - level connectivity: anti-line HUB-HUB ordinary port - Level connection: positive line HUB-SWITCH: Anti-line HUB (cascaded port) -Switch: positive line Switch-Switch: anti-line Switch-router: Positive Row Router-Router: The reverse lines and hub already have intelligent resolution, so the positive line overline can be used normally, otherwise the signal cannot be transmitted. Here is the following steps: as a standard specification at 100MB / s EIA / TIA 568B. Step 1: Using the twisted pair length required to cut the mourth, at least 0.6 meters, up to 100 meters. Then use the twisted palains (actually useless shears) to remove the outer skin of the twisted pair to 2-3 cm. There are some twisted pair cables contain a soft nylon rope. If you are stripping the outer skin of the twisted pair, I feel that the bare part is too short, and when it is not conducive to the production of RJ-45 connections, I can grasp the twisted pair. The outer skin, then pinch the nylon wire to the bottom of the outer skin, you can get a long bare line. Step 2: The twisted pair cable after the stripping is completed, as shown on the right. Step 3: Next, the dial operation is to be performed. The orange pair of bare twisted pairs is bullive in front of their own, and the brown line is bullive in its own direction, and the green pair of green pair is stripped to the left, and the blue line is stripped right, as shown.
On: Orange Left: Green: Brown Right: Blue Step 4: Place the green pair of lines with blue to the middle position, while orange pairs and brown lines keep do not move, that is, the location, such as Down shown. Adjusting the line is the order of the following: Orange left two: blue left three: green left four: Brown Step 5: Be careful to peel off each pair, white mix line front. Because we follow the standard of EIA / TIA 568B to make a joint, the line is a certain order (as shown). It is important to note that the green line should span the blue pair. The most easily mistaken here is to put the white-green line to the green line, which causes crosstalk to reduce the transmission efficiency. From left: Orange White / orange / white and green / blue / white, blue / green / white brown / brown common error connection is green line into the fourth position of the foot (as shown). The location of the green line should be placed in the 6th foot is correct, because in the 100BaseT network, the third feet are the same pair with the sixth feet, so the same pair is required. (See Standard EIA / TIA 568B): White Orange / Orange / White / Blue / Blue / Green / White Brown / Brown Step 6: Rear in the scissors or oblique clamps with scissors or oblique clamps The length of about 14 mm, leaving this length in order to comply with EIA / TIA standards, you can refer to the introduction of the RJ-45 joint and twisted pair production standards. Finally, each line of the twisted pair is placed in the pin of the RJ-45 joint. The first pin should be placed on white, the rest, as shown in Figure 7: Determine the twisted pair After each line is properly placed, the RJ-45 connector can be pressed by the RJ-45 ribs, such as a protective cover of the RJ-45 joint on the right picture, which prevents the joints from pushing when pulling. When using this protective case, you need to insert this jacket on the twisted pair cable before pressing the RJ-45 joint, as shown. Step 8: Repeat steps 2 to 7, and then produce the RJ-45 joint of the other end. Because the workstation and the hub are directly docked, the pin connection of the other end RJ-45 joint is exactly the same. The RJ-45 connector on both ends of the finished connection regardless of the pin and colors, this connection method also applies to the connection between the ADSL MODEM and the computer network card, the connection between the computer and the hub (switch). The completed RJ45 connector should be used as the cross-network cable shown in the following figure for the connection of the ADSL MODEM and the hub HUB (which is related to the modem design, not all), the Hub and HUB do not pass the level of connecting, and two The computer is connected to each other directly through the NIC. The production method is basically the same above, but it is not like 568b on the line, which is a manner of using 1-3, 2-6, which is made of 568B, and the other use 568a production, we should also know that The length should not exceed 100 meters, and the HUB level should not exceed 4 levels. Because the cross line is less used, it should be specifically marked, so as not to malfunction in the future, it causes a line failure. Finally, the line must be turned off, and the four green lights should be blinked in turn with the RJ-45 liner. The most common way for software debugging is to use the ping command.
