Many friends have many questions about how many meters to transmit to the POE transmission switch, so today we will learn about this knowledge together.
First, POE switch definition
POE is an acronym for Power over Ethernet, which refers to some IP-based terminals (such as IP phones, WLAN access points, APs) without any changes to the existing Ethernet Cat.5 cabling infrastructure. Network cameras, etc.), while transmitting data signals, can also provide DC power for such devices, that is, switches that support Power over Ethernet; that is, Power over Ethernet. In many cases, because it is inconvenient to deploy power or deploy power, the cost of power is too high, and the power consumption is improved. Therefore, PoE is considered to supply power to related devices through the network cable. Most of the time, POE-powered devices include IP surveillance cameras, wireless APs, and IP phones. The power of the devices is different and may require different standard PoE devices. The most commonly used PoE standards are IEEE802.3af (15.4W) and IEEE802.3at (25.5W).
Second, the standard POE switch transmission and power supply distance
As we all know, the Ethernet standard stipulates that the transmission distance is up to 100 meters. If it exceeds 100 meters, data delay and packet loss may occur. Because the signals are transmitted in the twisted pair, they interfere with each other and are also subject to external electromagnetic waves. Interference, and signal attenuation and distortion due to parasitic capacitance and parasitic inductance between the wires, the signal attenuation accumulated after the distance is too long will not guarantee the signal transmission.
However, not all network cables are limited to 100 meters. In actual operation, the network cable can also transmit more than 100 meters. The good quality can reach 120 meters, that is, the oxygen-free copper Cat.5 network cable, or the 6-type network cable. This kind of line can effectively reduce its own interference, and also avoid the interference caused by the series and the outside world. Therefore, the transmission is farther. In fact, the distance of the power transmission distance depends on the quality of the network cable. It is purely for the power signal transmission. More than one hundred meters, even up to 200 meters.
Category 5 is the most common type of cable on the market today, but the quality varies greatly. In order to reduce the cost, many manufacturers replaced the copper wire with impurity copper, copper-clad iron and copper-clad steel, resulting in a decrease in the transmission distance of the cable. If you want to maximize the effectiveness of PoE, be sure to use a good quality cable.
Now many PoE manufacturers have launched POE switches with a distance of 150 meters, a long distance of 250 meters, and even a transmission distance of 500 meters. Doesn't it mean that the standard POE switch has a transmission distance of 100 meters? And the actual use should try to control the distance within 80 meters. What is going on? Let's take a look at it.
Third, 150 meters transmission distance for POE switch quality requirements
As mentioned above, the PoE power supply distance is determined by the transmission distance of the data signal. The pure power can be transmitted very far, but the transmission distance of the data signal is determined by the network cable. The general Category 5 line data signal transmission distance is probably It is about 100 meters. In order to ensure the construction quality, the project generally takes 80-90 meters. Please note that the transmission distance here refers to the maximum rate, such as 100M.
Many manufacturers have indicated that their POE switches can reach a distance of 150 meters. However, in practical applications, ordinary POE switches must have a transmission distance of 150 meters. There are strict requirements on the quality of the network cable. The cost of use, even if the POE switch internal circuit uses a very common network switch chip and POE power management chip, in order to reach the network 100M and 150 meters transmission distance, even if the use of high-quality network cable, it is impossible, even if barely used, The power consumption of the PoE power supply is increased, and the power consumption of the PoE power supply is very unstable. The packet loss is severe, the transmission bandwidth and the signal are severely attenuated, resulting in unstable signals. The PoE switch equipment is aging and the maintenance is difficult.
Fourth, POE switch 250 transmission distance is going on
As mentioned above, even a high-performance POE switch 100M can only reach 150 meters with full load and stable transmission. What is the transmission distance of 250 meters? In fact, there are some methods. If the rate is reduced to 10M, that is, the transmission bandwidth is 10M. The transmission distance can be extended to 250 meters (depending on the quality of the network cable). This technology does not provide high bandwidth. The bandwidth is compressed from 100M to 10M, which makes it difficult to monitor the high-definition transmission of images.
While many manufacturers are promoting their products to support 250 meters of transmission, they do not mention the drop to 10M bandwidth, and there is a suspicion of deliberate concealment from customers.
When a POE switch transmits 250 meters, a switch is generally designed for the user to choose whether to use.
Not all POE switches can easily transfer 250 meters as long as they are reduced to 10M bandwidth. This depends on the quality of the switch. If the switch's internal switch chip is too poorly adaptive and the power chip management capability is not strong, even if 10M transmission is forced, It is also impossible to guarantee a stable transmission of 250 meters, even 150 meters. We once purchased a POE switch called 250m transmission on the Internet. It uses a super five-class strict standard network cable. The transmission of the network signal of 130 meters or more is gone, and we can't talk about 250 meters.
Five, how to ensure that POE switch 250 meters stable transmission
(1) POE power management
Due to the transmission distance requirement of 250, POE adopts high-power design, POE power chip adopts imported high-quality industrial grade chip, power management module can intelligently and automatically recognize IEEE802.3af/at standard, automatic power adjustment, and adopt 8-core intelligent power supply technology. To achieve such a function, the built-in power supply, the advantage of using the built-in power supply is that it can optimize the specific design, automatically measure the power requirements of the power receiving end and the cable transmission impedance, etc., and analyze and calculate the intelligent power management module to issue commands to the internal power supply circuit. Adjust the linear voltage input to match the automatic power output to the end powered device. Due to the extension of cable distance, the probability of cable damage is increased. Overcurrent/overvoltage protection circuit is also designed. At the same time, POE standard design ensures that non-POE equipment only transmits data, does not supply power, is stable and reliable, and eliminates Burning machine.
(2) Network transmission
It is very difficult for a common switch to reach a transmission of 250 meters, and it is necessary to have strict requirements on the network cable. If the quality of the network cable is slightly worse, the transmission distance will be greatly reduced. (Original title: How to correctly view the POE switch 150 meters, long distance 250 meters transmission)
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