Small network cables are also asked by universities. You can`t ignore them. Professional
Network Cable manufacturer Kewell tells you that network cables have transmission distances. For example, in the integrated wiring specification, the horizontal wiring must not exceed 90 meters, and the total link length must not exceed One hundred meters, that is, one hundred meters is a limit for wired Ethernet, and this limit is the length of the link from the network card to the hub device. Twisted pair has a transmission distance of "one hundred meters" that is "insurmountable", whether it is a Category 3 twisted pair with a transmission rate of 10 meters, or a Category 5 twisted pair with a transmission rate of 100 meters, or even a transmission rate of one kilometer. The effective transmission distance is 100 meters. The physical factors of the twisted pair largely determine the quality of the network cable. Inferior network cables often use unqualified twisted pair core wire winding methods, and cheap metal The core wire achieves the purpose of cutting corners, and this irresponsible behavior directly aggravates the interference of the network signal in the network cable, so that the effective transmission distance of the network cable is far less than 100 meters, and it will also affect the stability of the network transmission and the network cable. Service life etc.
When using PoE power supply, why does it stipulate that the length of the network cable shall not exceed 100 meters? However, in actual construction, in order to ensure the quality of the project, it is generally 80-90 meters. Please note that the transmission distance here refers to the rate, such as 100M. If the rate is reduced to 10M, the transmission distance can usually be extended to 150-200 meters, so the PoE power transmission distance is not determined by PoE technology. It is determined by the type and quality of the network cable. Although in actual construction, a better quality network cable can break the 100-meter distance limit and the equipment can work normally, this approach is not recommended. Because some potential problems do not appear immediately, but slowly appear over time, which will cause follow-up maintenance problems. In simple cases, such as bandwidth upgrades, devices that can work normally at distances of more than 100 meters will not work properly after the network speed is greatly increased.
How did the network cable transmit the distance of 100 meters? What caused the 100-meter transmission distance limit for twisted-pair cables? It is necessary to delve into the deep physical principles of twisted pair. The transmission of the network is actually the transmission of the network signal on the twisted pair. As an electronic signal, when it is transmitted in the twisted pair, it must be affected by resistance and capacitance, which leads to the attenuation and distortion of the network signal. When the signal attenuation or distortion reaches a certain level, it will affect the effective and stable transmission of the signal. Therefore, the twisted pair cable has a transmission distance limit, so how do you calculate the upper limit of 100 meters? Category 5 UTP and Category 5 UTP are mainly for computer network services. According to the 100Base-TX regulations of Fast Ethernet, the communication rate is 100mbps.
There are devices at both ends of a link. These two devices may send data at the same time, causing conflicts. At this time, the conflict domain is 2. Data packets will be lost due to conflicts. In order to avoid packet loss caused by conflicts, Ethernet uses conflict detection and back-off retransmission technology. In order to back off and retransmit, it must be ensured that one end can detect the conflict before transmitting a data packet. The influence of cable type and quality on transmission distance + what we are talking about is the three types of lines, five types of lines, seven types of lines... Cables are twisted tighter and tighter, and there are more and more spacers between pairs (cross frame, aluminum foil, Mylar, drain wire, copper wire mesh), and the frequency ranges from 16MHz to 100MHz, 250MHz, 500MHz, 600MHz and many more. +When the frequency increases, the crosstalk phenomenon becomes more and more serious. This requires increasing the diameter of the copper wire, increasing the torque of the cable, increasing the cross frame to separate the cables, increasing the thickness of the outer sheath or increasing the shielding layer Wait for various production processes to solve the increasingly difficult crosstalk problem.It has to be said that crosstalk makes the cable structure more and more complicated. Category 5 cables are common standard cables on the market, but the quality of different cable manufacturers differs greatly. Which cable manufacturer is better? It must be ranked by professional network cable manufacturers. The network cable produced by Kaiweier is good, with 99.99% oxygen-free copper conductors. Under the trend of price wars, many manufacturers use copper-clad iron and copper-clad copper wires in order to reduce costs. The replacement of steel leads to a decrease in the transmission distance of the network cable, and even network instability, packet loss, etc., and equipment manufacturers are often in the dark, which is really wrong. Therefore, if PoE is to be effective, a good quality network cable must be used. Large losses affect the overall quality of the project.
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