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Practices and connection of twisted pair wires
Commonly used network cables include twisted pair coaxial cable and optical fiber cables. twisted Pair wires can be divided into shielded twisted pair wires (STP) and unshielded twisted pair wires (UTP) based on whether they are added with the screen of the wire mesh sleeve ). most local networks use unshielded twisted pair wires (UTP-unshielded twisted pair red) as the transmission medium for cabling.
UTP network cable consists of a certain length of twisted pair wire and RJ-45 crystal head.
Twisted Pair wires are divided into 4 pairs by eight copper wires of different colors. The main cause of twisted pair is to minimize the impact of electromagnetic radiation and external electromagnetic interference. in EIA/TIA-568 standards, the twisted pair wires are divided into three types of four category five category lines according to electrical characteristics. three types of cables and five types of cables are most commonly used in the network. Currently, more than six types of cables exist.
Good network cable to the RJ-45 crystal head into the network card or hub and other network equipment RJ-45 socket. correspondingly, the RJ-45 plug-in seat is also divided into three types or five types of electrical characteristics. RJ-45 crystal head consists of metal and plastic, the production of cable need RJ-45 crystal connector front end has 8 groove, referred to as "8 p" (Position, position ). there are a total of 8 metal contacts in the groove, referred to as "8C" (contact, contact), so the industry has a "8p8c" alias. special attention is the RJ-45 crystal head pin number, when the metal face us from left to right PIN number is 1 ~ 8. The serial number is very important for network connections and cannot be mistaken.
The maximum transmission distance of twisted pair wires is M. to increase the transmission distance, a repeater can be installed between two twisted pair wires. A maximum of four Relay Links can be installed. if four reconnections are installed to connect five CIDR blocks, the maximum transmission distance is 500 mb.
The wiring standards of EIA/TIA define the line sequence 568a and 568b of the two twisted pair wires, as follows:
Green-1, green-2, orange-3, blue-4, blue-5, orange-6, brown-7, brown-8
Orange-1, orange-2, green-3, blue-4, blue-5, green-6, brown-7, brown-8
To maintain optimal compatibility, the EIA/TIA 568b standard is widely used to create network cables. A wiring method is applied in the whole network wiring, but the network connection with both ends of the RJ-45 plug-in is feasible in both the 568a standard and 568b standard. the order of the twisted pair with the pin serial number of the RJ-45 header-a pair of fit. 10 M Ethernet cable uses 1 2 3 6 serial number core line to transmit data, while M Nic uses four pair lines. the 10 m Nic can be created in M mode, and the twisted pair wires provide four pairs. Therefore, even if the 10 m Nic is used, the 10 m Nic is generally created in M mode.
The, and cables must be twisted pair. this is because, in the transmission of data, in order to reduce and suppress external interference, the transmitted and received data are transmitted in a differential manner, that is, each pair of lines twisted together to transmit a differential signal (this is also the name of the twisted pair ).
The so-called differential signal refers to a line that transmits signals in the positive-electric square mode, and the other line transmits the same signal in the negative-level mode. When there is an interference signal in the line, the effect on the two wires is the same. Therefore, the interference signal can be shielded when the receiver restores the differential signal (which can be understood as the two differential signals for subtraction ). the interference suppression principle of twisted pair wires shows that each pair of wires is used to suppress interference signals and improve transmission quality. therefore, when creating a twisted pair connection, do not separate a pair of wires that transmit differential signals. Otherwise, the transmission quality of the network will be greatly affected.
The following describes how to create twisted pair wires in several application environments.
1. connection between an Ethernet NIC and a hub (or vswitch:
When a network device, such as a PC, is connected to the hub, the network cable is a direct line. both ends of the twisted pair wires must be produced according to the same standard, either EIA/tia568a, or 568b.
2. the cascade ports of the hub (or vswitch) are connected to the common ports of other hubs (or vswitches:
A dedicated connection port exists in the hub and vswitch that support cascade connections. The cascade ports are used to connect the hub or vswitch of the next level. the network cable used for connection is a direct line, which is the same as the method described earlier.
3. Connect the Hub (or vswitch) or two computers directly:
The cross line is used for connection between hubs or direct computer connection. When the cross line is made, one end is made according to the EIA/tia568a standard, and the other end is made according to the 568b standard. the cross line is rarely used, so special marking should be made to avoid future use of the direct line, resulting in line failure.
After the twisted pair wires are created, the line must be disconnected. When the cable tester is used for testing, all green lights should flash in turn. the most common method for software debugging is to use the ping command that comes with windows. if the workstation receives a response from the server, it indicates that the line is normal and the network protocol is installed normally, which is the basis for the normal operation of network application software.
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