The RJ-45 connector consists of a plug and a jack (or receptacle). The jack is mounted on the machine, while the plug and the connecting wire are connected. The wiring standard developed by EIA/TIA specifies the number of 8 pins. If you look at the plug and the end of the plug is facing the eye, and the contact point of the pin is underneath the plug, then the leftmost is (1) and the rightmost is (8).
Pin 1 ----- transmitted
Pin 2 ----- transmitted
Pin 3 ----- receive
Pin 4 ----- do not use
Pin 5 ----- do not use
Pin 6 ----- receive
Pin 7 ----- do not use
Pin 8 ----- do not use
Crystal head
There are strict regulations on the color code and arrangement method of twisted pair wires, and TIA/EIA568B is now commonly used. The following sequence should be used when bonding: (TIA/EIA568B)
1-----> White-orange
2----->橙
3-----> white-green
4-----> Lotus
5-----> Hakuren
6----->绿
7-----> White Thorn
8----->棕
In addition, if the two ends of the cable are connected one-to-one, a group of signals (negative voltage signals) will be transmitted through two cores that are not twisted together, resulting in a large amount of near-end crosstalk (NEXT->Near-end-crosstalk), so it should be wired in accordance with international standards.
LAN is to connect separate computers or terminals to each other using communication lines, follow a certain protocol, exchange information, and realize resource sharing. Among them, communication lines, that is, transmission mediums, are commonly used: twisted pair, coaxial cable, optical fiber, etc. From the perspective of cost performance and maintainability, most LANs use unshielded twisted pair (UTP) as the transmission medium for cabling.
Cable
The network cable consists of a twisted pair cable with an RJ45 crystal header at a certain distance. The twisted pair consists of 8 wires of different colors divided into 4 pairs twisted together, and the function of twisting in pairs is to reduce the influence of electromagnetic radiation and external electromagnetic interference as much as possible.
Twisted pairs can be divided into shielded twisted pair (STP) and unshielded twisted pair (UTP) depending on whether they are shielded with a metal mesh sleeve.
The outer layer of the shielded twisted pair cable is wrapped by aluminum-platinum to reduce the radiation, but it does not completely eliminate the radiation, and the shielded twisted pair is relatively expensive and more difficult to install than the unshielded twisted pair cable.
Unshielded twisted pair cables offer the following advantages: unshielded jacket, small diameter to save space, light weight, easy bending, easy installation, minimal or eliminated near-end crosstalk, flame retardant, independence and flexibility for structured cabling.
The common models of twisted pair are as follows:
Class 1 (CAT1): Mainly used for voice transmission (Class 1 standards were mainly used for telephone cables before the early eighties), different from data transmission.
CAT2 LINE: WITH A TRANSMISSION FREQUENCY OF 1MHZ, IT IS USED FOR VOICE TRANSMISSION AND DATA TRANSMISSION AT A MAXIMUM TRANSMISSION RATE OF 4MBPS, AND IS COMMONLY FOUND IN OLDER TOKEN NETWORKS THAT USE THE 4MBPS SPECIFICATION TOKEN PASSING PROTOCOL.
Category 3 (CAT3): Transmission frequency 16MHz, for voice transmission and data transmission with a maximum transmission rate of 10Mbps, mainly for 10BASE--T, cables specified in ANSI and EIA/TIA 568 standards.
Category 4 Line (CAT4): The transmission frequency is 20MHz for voice transmission and data transmission up to 16Mbps, mainly for token-based LANs and 10BASE-T/100BASE-T.
CAT5: The transmission frequency is 100MHz, which is used for voice transmission and data transmission with a maximum transmission rate of 100Mbps, mainly used for 100BASE-T and 10BASE-T networks. This is the most commonly used Ethernet cable, which has an increased winding density and is coated with a high-quality insulating material. The wire skin is marked with the word CAT5, and the single strand copper core is 24AWG.
CAT5e: 100MHz transmission frequency, mainly used for Gigabit Ethernet (1000Mbps). With reduced attenuation, less crosstalk, and higher attenuation-to-crosstalk ratio (ACR) and signal-to-noise ratio (StructuralReturn Loss), and a smaller time delay difference, the performance is greatly improved. It is currently the most widely used type of network cable, such as the super five network cable of Intco Tong. The wire skin is marked with the words CAT5E or 5E, and the single strand copper core is 24AWG.
CAT6: Transmission frequency of 250MHz, most suitable for applications with transmission rates above 1Gbps, mainly for Gigabit Ethernet (1000Mbps). Category 6 twisted pair has certain differences from Category 5 or super 5 twisted pair in shape and structure, not only increasing the insulated cross skeleton, placing the four pairs of twisted pair wires in the four grooves of the cross skeleton, and the diameter of the cable is also thicker. The wire skin is marked with the word CAT6, and the single strand copper core is 23AWG.
CAT6A: The transmission frequency is 200~250 MHz, and the maximum transmission speed can also reach 1000 Mbps, which is mainly used in gigabit networks. CAT6e is an improved version of CAT6, which is also an unshielded twisted pair cable specified in ANSI/EIA/TIA-568B.2 and ISO CAT6/E standards, which has greatly improved crosstalk, attenuation and signal-to-noise ratio. The single strand copper core is 23AWG. Another feature is the addition of a cross-shaped pair separator between the 4 twisted pair pairs. Without cross separation, one pair of wires in a cable can get caught in the gap between two wires of the other pair, reducing the spacing between pairs and exacerbating crosstalk problems. Together with the outer sheath of the cable, the divider holds the 4 pairs of conductors tightly in place for which they were designed and reduces the loosening of the pair due to cable bending, thus reducing performance degradation during installation.
CAT7: Transmission frequency up to 500 MHz and transmission rate up to 10 Gbps, it is mainly designed to adapt to the application and development of 10 Gigabit Ethernet technology. This wire is the newest type of shielded twisted pair in the ISO Class 7/Class F standard.
The price of different types of twisted pair cables varies greatly or even widely, and the application range is also very different.
In addition to the traditional voice system, which still uses Category 3 twisted pairs, network cabling is currently basically using Category 5 or 6 unshielded twisted pairs. Although the Category 5 unshielded twisted pair cable can still support 1000Base-T, it has gradually faded out of the cabling market because it is almost the same as the Category 5 unshielded twisted pair cable in terms of price.
Although the price of Category 6 unshielded twisted pair cable is higher, it is slowly becoming the new favorite of integrated cabling because of its very good compatibility with Category 5e cabling system and its ability to support 1000Base-T very well. Category 7 shielded twisted pair cable is a completely new cabling system, although it has excellent performance, but it is expensive because of its price. The construction is complex and there are few products to choose from, so it is rarely used in wiring engineering. If you consider the future application needs of the network, theoretically the most advanced cabling products should be installed, because it is often difficult to update and replace after installing cables, basically, a cabling system should be applied for at least 10 years as a standard, which can support the performance update of 4 to 5 generations of network equipment, if the future network equipment needs better cables to improve data speed.
The crystal head is connected to the network cable
The EIA/TIA cabling standard specifies the wire sequences 568A and 568B for two twisted pairs.
Standard 568A: White-green--1, green--2, white-orange--3, blue--4, white-blue--5, orange--6, white-brown--7, brown--8.
Standard 568B: White Orange - 1, Orange - 2, White Green - 3, Blue - 4, White Blue - 5, Green - 6, White Brown - 7, Brown - 8;
One cabling method is applied in the entire network cabling, but the network connection with RJ-45 plugs at both ends is common in the network, regardless of whether it is terminated in either A or B. The order of the twisted pair corresponds to the pinout number of the RJ45 head. The 10M Ethernet cable uses 1, 2, 3, and 6 cores to transmit data, and the 100M Ethernet cable uses 4, 5, 7, and 8 cores to transmit data. Why are 4 pairs (8 cores) twisted pair cables used today? This is mainly to accommodate a wider range of uses, and to meet the wiring requirements of a wide variety of user equipment without changing the infrastructure. For example, we can use one of the twisted wires at the same time for voice communication. The 100BASE-T4 RJ-45 specification for twisted pair is as follows:
1, 2 is for sending, 3, 6 is for receiving, 4, 5, 7, 8 are bidirectional lines.
1 and 2 wires must be twisted pairs, 3 and 6 twisted pairs, 4 and 5 twisted pairs, and 7 and 8 twisted pairs.
The following describes the production methods of twisted pair in several application environments.
MDI indicates that the port is a cascading port, and MDI-X indicates that the port is a common port.
1) When the PC and other network devices are connected to the HUB, the network cable used is a straight-through line, and the two ends of the twisted pair cable should be connected one-to-one, at this time, the HUB is the MDI-X port, and the PC is the MDI port. The 10Mbps network cable only needs to correspond to the two ends of the twisted pair cable one by one, and there is no need to consider the sorting of different colored lines, and if the 100M rate is used, it must be made in strict accordance with the EIA/TIA 568A or 568B wiring standard.
2) When cascading between HUBs, the control switch of the cascade port should be placed on the MDI (Uplink) and connected with a straight cable at the same time. If the HUB does not have a dedicated level connection, or can not use the level connection, must use the MDI-X port connection, at this time, we can use the crossover cable to achieve the purpose, here the crossover line, that is, when making the network cable, use the 1 pin of one end of the RJ-45 plug to connect to the 3 pins of the RJ-45 plug at the other end, and then use the 2 pins of the RJ-45 plug at one end to connect to the 6 pins of the RJ-45 plug at the other end. It can be made according to the following chromatogram:
A-side: white orange, orange, white-green, blue, white-blue, green, white-brown, brown;
B-end: white-green, green, white-orange, blue, white-blue, orange, white-brown, brown.
At the same time, we should also know that the length of the network cable between the cascading hubs should not exceed 100 meters, and the cascading of the hubs should not exceed 4 levels. Because the crossing line is rarely used, it should be specially marked to avoid being mistakenly used as a through line in the future, resulting in line failure. In addition, the crossover cable can also be used for direct connection between two microcomputers.
Finally, the line must be tested on and off, and when tested with RJ-45 line tester, all 4 green lights should flash in turn. The most common way to debug software is to use the Ping command that comes with Windows. If the workstation gets a response from the server, it means that the wiring is normal and the network protocol installation is normal, which is the basis for the network application software to work properly.