Wire sequence of RJ45 plug

568A standard

Pin sequence media directly connected signal color

1 TX+(transmission) white green

2 TX - (transmission) green

3 RX+(receive) white orange

4. Do not use blue

5. Do not use white or blue

6 RX - (Receiver) Orange

7. Do not use white brown

8. Do not use brown

568B standard

Pin sequence media directly connected signal color

1 TX+(transmitting white orange)

2 TX - (Transmission) Orange

3 RX+(receive) white green

4. Do not use blue

5. Do not use white or blue

6 RX - (receive) green

7. Do not use white brown

8. Do not use brown

5 colors Twisted pairs can play an anti-interference role!!!!! Among the 8 wires of the Ethernet cable, 1236 are used for transmitting digital signals, which are used for our network data transmission. 45 are analog signals, which are telephone pulse signals. 78 are used to power IP phones. Of course, POE support is required. In fact, under 100M network operation, usually all 8 cores will be used because 100M network transmission requires high line requirements, not only 1, 3, 2, 6, otherwise the network operation will be unstable.

Understand the principle and practice of Category 5e twisted pair cables

1、 Firstly, let's have a specific understanding of what twisted pair cables are

1. Twisted pair cable: As a transmission medium, it is composed of two thin copper wires wrapped in insulating material and wound together in a certain ratio.

The relevant images for this topic are as follows:

The picture shows Category 5e twisted pair cables, consisting of four pairs of intertwined wires, totaling eight wires.

2. Why twist two wires in pairs?

Because this mutual entanglement changes the original electronic properties of the cable. This not only reduces its own crosstalk, but also maximizes the prevention of interference from signals on other cables on this pair of cables.

3. Twisted pair cable classification:

1) Twisted pair cables can be divided into 2 pairs, 4 pairs, and 25 pairs based on the number of twisted pairs. (For example, 2 pairs are used for telephone, 4 pairs are used for network transmission, and 25 pairs are used for large number cables in telecommunications communication)

2) It can be divided into two categories based on whether there is a shielding layer: shielded twisted pair (STP) and unshielded twisted pair (UTP).

3) According to frequency and signal-to-noise ratio, it can be divided into 3 categories, 4 categories, 5 categories, and super 5 categories. Nowadays, many places have already used Category 6 or even Category 7 cables. At least three or more categories are used in computer network communication. The following are descriptions of various types of lines:

Category 1: Mainly used for transmitting voice (Category 1 standards were mainly used for telephone cables before the early 1980s), not for data transmission.

Category 2: Transmission frequency of 1MHz, used for voice transmission and data transmission with a maximum transmission rate of 4Mbps, commonly found in old token networks that use the 4Mbps standard token passing protocol.. I"

Category 3: Refers to the cables currently specified in ANSI and EIA/TIA568 standards. The transmission frequency of this cable is 16MHz, used for voice transmission and data transmission with a maximum transmission rate of 10Mbps, mainly for 10base-T

Category 4: This type of cable has a transmission frequency of 20MHz and is used for voice transmission and data transmission with a maximum transmission rate of 16Mbps. It is mainly used for token based LANs and 10base-T/100base-T

Category 5: This type of cable has increased winding density and is covered with a high-quality insulation material. It has a transmission frequency of 100MHz and is used for voice transmission and data transmission with a maximum transmission rate of 100Mbps. It is mainly used for 100base-T and 10base-T networks and is the most commonly used Ethernet cable.

4. The performance indicators of twisted pair cables are what users are most concerned about, which are several indicators that characterize their performance. These indicators include attenuation, near end crosstalk, impedance characteristics, distributed capacitance, DC resistance, etc.

(1) Attenuation. sixty

Attenuation is a measure of signal loss along a link. The attenuation is related to the length of the cable, and as the length increases, the signal attenuation also increases. Attenuation is measured in decibels and represents the ratio of signal strength from the transmitting end to the receiving end. Due to the frequency dependent attenuation, it is necessary to measure the attenuation at all frequencies within the application range.

(2) Near end crosstalk+:

Crosstalk is divided into near end crosstalk and far end crosstalk (FEXT). The tester mainly measures NEXT, and due to the presence of line losses, the impact of FEXT values is relatively small. Near end crosstalk (NEXT) loss is the measurement of signal coupling from one pair of wires to another in a UTP link. For UTP links, NEXT is a key performance indicator and also the most difficult to measure accurately. As the signal frequency increases, its measurement difficulty will increase.

2、 Category 5e unshielded twisted pair cable

The basic cables we use in computer communication networks today are "Category 5e unshielded twisted pair cables". The two ends of the cable are pressed into the RJ45 crystal head in a certain wire sequence, which is commonly known as the "Ethernet cable".

The picture shows an RJ45 crystal head!

1. What are T568A standard and T568B standard?

These are two international standard line sequences developed for Category 5e twisted pair cables to achieve performance indicators and unified wiring specifications.

(Imagine: when making RJ45 crystal heads, if there is no such standard, then when one end of a network cable made by someone else has a problem with the crystal head, you have to check the wire sequence on the other end before coming back to make the RJ45 crystal head on this end. How troublesome it is.). And it is very likely to cause crosstalk due to not using the correct winding. ）

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The line sequence of T568A is: white green, green, white orange, blue, white blue, orange, white brown, brown

The line sequence of T568B is: white orange, orange, white green, blue, white blue, green, white brown, brown

2. Parallel and intersecting lines (reverse wiring)

1) Let's first take a look at how these two types of threads are made:

Both ends of the parallel line use the same wiring standard. Under normal circumstances, the industry uses the T568B standard! Remember!!! One end of the crossover uses T568A line sequence, while the other end uses T568B line sequence.

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