Do crystal heads every day, do you know what the 8-core network cable does?

When many friends connect the network cable, they usually don't know the eight copper wires in the network cable, which ones are the ones that ensure the normal transmission of the network?

1. Line sequence and transmission distance

The first thing to know is the overall function of the eight copper wires. In order to reduce the mutual interference of electromagnetic signals, the eight copper wires are twisted together at a certain density. In this way, when transmitting electrical signals, the radio waves radiated from each other will cancel each other out, effectively eliminating interference. The name twisted pair is also derived from this structure.

The earliest application of twisted pair was used for the transmission of telephone signals, and then it was gradually introduced into the transmission of digital signals. Now, Category 5e twisted pair and Category 6 twisted pair are widely used. Category 5e and Category 6 lines can reach a bandwidth of 1000Mbps. The only disadvantage of twisted pair is that the transmission distance is relatively short, generally up to 100 meters, and a better line is about 120 meters.

Generally, Category 5 over Category 5 twisted-pair cables need to use four pairs of wires, that is, 8 core wires. Below 100M, generally use 1, 2, 3, 6, four wires.

Main line (standard 568B): The line sequence at both ends is the same, and the line sequence is: orange-white, orange, green-white, blue, blue-white, green, brown-white, brown.

Reverse line (568A): One end is the line sequence of the positive line, and the other end is: green-white, green, orange-white, blue, blue-white, orange, brown-white, brown.

It is not necessary to memorize the line sequence of 568A for monitoring. This line sequence is no longer used for one, and for the other, just swap 13 and 26 on the basis of 568B.

2. The role of each core

Specifically why four 1236 wires are used, then we need to understand what the function of each core is:

1 output data (+)

2 Output data (-)

3 Enter data (+)

4 Reserved for phone use

5 Reserved for phone use

6 Enter data (-)

7 Reserved for phone use

8 Reserved for phone use

It can be seen that although the twisted pair has 8 core wires, in the currently widely used 100M network, only 4 of them are actually used, namely the 1st, 2nd, 3rd, and 6th, which are respectively It plays the role of receiving and sending signals. 4, 5, 7, and 8 are two-way lines, reserved for use.

However, when the network runs above 100M, usually all eight cores will be used. For example, not only 1 3 2 6 but also eight cores need to be used for Category 6 and Category 6 cables, otherwise the network operation will be unstable.

Stripping the network cable, we can find that the winding density of the four pairs of twisted pairs is not the same. The orange and green pairs used to transmit data have significantly more winding turns than the brown and blue pairs used for grounding and other public purposes, so it is recommended When you usually make jumpers, arrange them strictly in the order of 568B.

In fact, there is another key problem: when many unscrupulous businesses now produce network cables, only four of the 8 cores use pure copper, while the remaining four cores do not use copper-clad aluminum, copper-clad steel, or even copper-clad iron.

Somehody said: "I just like to make threads in the order I am used to. Is it also possible to use it?"

This way you can use it casually at home, if you are more strict in engineering, follow the line sequence. Otherwise, the role of the twisted pair will be lost. The data transmission attenuation is serious, and the transmission distance is greatly reduced.