What is a PoE Switch and How Does it Work?
A PoE (Power Over Ethernet) switch is a switch that can transmit data signals to some IP-based terminals (such as IP phones, wireless LAN access points AP, network cameras, etc.) without making any changes to the existing Ethernet Cat.5 wiring infrastructure, while also providing DC power to such devices.
PoE technology is also known as a power supply system based on a local area network (POL, Power over LAN) or Active Ethernet (Active Ethernet), and is sometimes referred to as Ethernet power supply.
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It uses existing standard Ethernet transmission cables to transmit data and electrical power at the same time. It is the latest standard specification and maintains compatibility with existing Ethernet systems and users.
The emergence of PoE switches has greatly simplified the power supply and installation process of network equipment, reduced wiring costs, and improved the reliability and flexibility of network equipment. It is widely used in many fields such as home networks, commercial applications, industrial applications, and public facilities.
Working Principle of PoE Switch
The working principle of PoE switch mainly involves the transmission of power and data signals, device detection, power evaluation, power supply control and power-off protection. The following is a detailed introduction to these working principles:
1. Transmission of power and data signals
PoE switch transmits power and data signals together to the device that needs power through Ethernet cable. During the transmission process, the PoE switch connects the power output to the Ethernet port and transmits DC power through the idle wire pair or data core wire in the Ethernet cable. At the same time, the PoE switch is also responsible for transmitting data signals to ensure the normal communication of network devices.
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2. Device detection
When a network device is connected to a PoE switch via an Ethernet cable, the PoE switch will first detect whether the device supports PoE technology. This is achieved by outputting a small voltage to the port and detecting the connection status of the cable terminal. If the device does not support PoE technology, the PoE switch will only transmit data signals and will not supply power. If the device supports PoE technology, the PoE switch will enter the next power evaluation stage.
3. Power evaluation
After detecting the powered device (PD), the PoE switch will classify the PD device and evaluate the power consumption required by the PD device. This is to ensure that the PoE switch can provide enough power to meet the power supply needs of the device while avoiding overload or insufficient power supply.
4. Power supply control
After completing the power evaluation, the PoE switch will start to supply power to the PD device from a low voltage until a stable 48V DC power supply is provided. During the power supply process, the PoE switch will control the voltage and current of the power supply according to the actual needs of the device to ensure the stability and reliability of the power supply. At the same time, the PoE switch will also monitor the power consumption of the PD device to prevent overload or insufficient power supply.
5. Power failure protection
If the PD device is disconnected from the network, the PoE switch will quickly (generally within 300-400ms) stop supplying power to the PD device and repeat the detection process to detect whether the end of the cable is connected to the PD device. This function can protect the PoE switch and PD devices from damage caused by power failure and ensure the stability and security of the network.
Power supply standards and power levels of PoE switches
The power supply standards of PoE switches are mainly based on the IEEE 802.3 series of standards, of which IEEE 802.3af and IEEE 802.3at are the two most commonly used standards.
1. IEEE 802.3af standard
The IEEE 802.3af standard is a new standard based on the Ethernet power supply system PoE. It adds relevant standards for direct power supply through network cables on the basis of IEEE 802.3. The standard stipulates that each PoE port can provide a maximum of 15.4W of power supply, which is suitable for low-power application scenarios.
2. IEEE 802.3at standard
The IEEE 802.3at standard is an extension of the IEEE 802.3af standard, providing a higher power level. The standard stipulates that each PoE port can provide a maximum of 30W of power supply, which is suitable for devices that require higher power, such as wireless access points, network cameras, etc.
In addition, there is the newer IEEE 802.3bt (PoE++) standard, which further expands the power transmission capacity of PoE, with each port transmitting up to 60W-90W, and even up to a power ceiling of 100W. This allows PoE technology to provide reliable power supply for more devices, such as medical equipment, industrial equipment, high-power LED lighting, etc.
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Applications and advantages of PoE switches
PoE switches are widely used in many fields such as home networks, commercial applications, industrial applications, and public facilities. The following is a detailed introduction to these application scenarios and advantages:
1. Home network
In a home network, a PoE switch can provide power supply for devices such as wireless routers, network cameras, and IP phones. This makes the home network more intelligent and convenient, and users do not need to purchase power adapters or power cables for each device separately, reducing wiring costs and maintenance difficulties.
2. Commercial applications
In commercial applications, PoE switches can power devices such as network cameras, wireless access points, and electronic signs. These devices usually need to be installed in higher places or in locations that are not easy to replace. Using PoE technology can greatly simplify installation and maintenance. At the same time, PoE switches can also provide stable power supply and data communication to ensure the reliability and security of commercial networks.
3. Industrial applications
In industrial applications, PoE switches can power industrial cameras, sensors, controllers and other equipment. These devices usually need to run for a long time and require high reliability. The use of PoE technology can reduce failure rates and maintenance costs, and improve the stability and production efficiency of industrial equipment.
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4. Public facilities
In public facilities, PoE switches can power smart lamps, smart door locks, smart billboards and other equipment. These devices are distributed over a wide area, and the use of PoE technology can simplify wiring and installation. At the same time, PoE switches can also provide stable power supply and data communication to ensure the intelligence and reliability of public facilities.
Selection and precautions of PoE switches
When choosing a PoE switch, users need to consider the following factors:
1. Number of ports and power level
Users need to choose the appropriate number of ports and power level according to actual needs. The number of ports should meet the current and future device connection requirements, and the power level should meet the power supply requirements of the equipment.
2. Power supply standards and compatibility
Users need to understand the power supply standards and compatibility of PoE switches. Different power supply standards have different power levels and transmission distance limits. Users need to ensure that the selected PoE switch matches the power supply standards and compatibility of the connected devices.
3. Brand and quality
Users need to choose well-known brands and high-quality PoE switches. Well-known brands and high-quality PoE switches have better performance and stability, and can provide more reliable power supply and data communication.
4. Price and cost-effectiveness
Users need to choose the right PoE switch according to their budget and needs. Price is not the only consideration, but users need to find a balance between performance and price and choose a cost-effective PoE switch.
When using a PoE switch, users also need to pay attention to the following:
- Ensure that the power supply standards and compatibility of the PoE switch and the connected device match.
- Avoid overload or insufficient power supply to ensure the stability and reliability of the PoE switch.
- Regularly check the operating status and connection status of the PoE switch to detect and solve problems in a timely manner.
Development Trend and Future Outlook of PoE Switches
With the continuous development and popularization of IoT technology, PoE switches, as an important part of IoT infrastructure, will usher in broader market prospects and development opportunities.
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The following are the development trends and future prospects of PoE switches:
1. Power level continues to increase
With the increasing number of IoT devices and the increasing power demand, the power level of PoE switches will continue to increase. In the future, PoE switches will support higher power levels to meet the power supply needs of more types of devices.
2. Intelligent and networked trends strengthen
In the future, PoE switches will be more intelligent and networked. By integrating more intelligent functions and network interfaces, PoE switches will be able to provide better device management and data communication capabilities to meet the needs of IoT applications.
3. Security and reliability are strengthened
With the increasing number of IoT applications and the increasing security requirements, the security and reliability of PoE switches will be strengthened. In the future, PoE switches will adopt more advanced security technologies and protection mechanisms to ensure the security and reliability of devices and data.
4. Application scenarios continue to expand
In the future, the application scenarios of PoE switches will continue to expand. In addition to traditional home networks, commercial applications, industrial applications and public facilities, PoE switches will also be used in more emerging fields, such as smart cities, smart transportation, smart homes, etc.
Summary
As a switch that can provide DC power to devices while transmitting data signals, PoE switches have broad application prospects and development opportunities. Through continuous technological innovation and market expansion, PoE switches will provide more reliable, efficient and intelligent power supply and data communication solutions for IoT applications.
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FAQs
A PoE switch is a switch that can add a DC power supply to an Ethernet cable, so that network devices can be powered directly through the network cable. It can not only transmit data signals, but also provide power supply for connected devices.
The working principle of a PoE switch is to connect the power output of the switch to the Ethernet port and transmit the power to the device that needs power through the Ethernet cable. At the same time, the PoE switch will determine the required power level according to the needs of the device and control the way and time of power supply.
An ordinary switch can only transmit data signals and cannot power devices. A PoE switch can transmit power and data signals to network devices together to provide power supply for the devices.
A PoE switch can provide power supply for devices that support PoE technology, such as IP phones, network cameras, wireless access points, etc.
Yes, PoE switches can be connected in series. When the front-end device has a power supply demand, the back-end device will output voltage to the front end.
Yes, but you need to use a Category 5e 8-core network cable, and the device needs to support the network extension (EXTEND) mode.
The power supply standards for PoE switches mainly include IEEE 802.3af and IEEE 802.3at, as well as the updated IEEE 802.3bt (PoE++). Among them, the IEEE 802.3af standard allows each port to provide a maximum of 15.4W of power supply, while the IEEE 802.3bt standard allows each port to provide up to 90W or even 100W of power.
The device will generally indicate whether it is a PoE device in the model, description or port. You can also check whether the device supports the PoE function by running specific commands (such as “display device” or “display version”).
Yes, a genuine Category 5e, Category 6 or Category 6e network cable is required when powering a PoE switch. At the same time, the equivalent impedance of the network cable also needs to meet the corresponding standards.
Category 5e 8-core cable, also known as Cat 5e cable, is a cable commonly used in network communications. It consists of 8 cores that are twisted together in a specific way to reduce electromagnetic interference (EMI) and signal attenuation. Each core is usually made of copper and has good conductivity.
The performance characteristics of Category 5e 8-core cable include:
Fast transmission speed: Supports transmission rates up to 1000Mbps, suitable for Gigabit Ethernet.
Strong anti-interference ability: Reduces electromagnetic interference through a specific twisting method and improves the stability of signal transmission.
Long transmission distance: Under standard conditions, the transmission distance can reach 100 meters.
Good compatibility: Compatible with a variety of network devices, such as switches, routers, computers, etc.
Category 5e 8-core cable is suitable for various scenarios that require high-speed and stable network transmission, such as offices, data centers, home networks, etc.
When choosing a high-quality Category 5e 8-core network cable, you should pay attention to the following points:
Check the specifications: Make sure the network cable meets the Cat 5e standard, and check the parameters such as the core material and diameter.
Test performance: Use a network tester to detect the transmission rate, attenuation and other performance of the network cable.
Choose a brand: Prefer well-known brands to ensure product quality and after-sales service.
When using Category 5e 8-core network cable, you should pay attention to the following points:
Correct connection: Make sure that the crystal heads at both ends of the network cable are correctly connected to the network device interface.
Avoid bending: Avoid excessive bending of the network cable to avoid affecting signal transmission.
Keep clean: Clean the network cable interface regularly to ensure a stable connection.
When maintaining Category 5e 8-core network cable, you should pay attention to the following points:
Regular inspection: Regularly check the appearance and performance of the network cable, and replace it in time if it is damaged.
Avoid moisture: Place the network cable in a dry environment to avoid moisture causing performance degradation.
Reasonable wiring: Reasonable wiring, avoid cable entanglement and extrusion, and ensure stable signal transmission.
Generally speaking, after welding Category 5e 8-core network cables of different brands, the network can still be unobstructed. However, in order to ensure the quality and stability of the network connection, it is best to choose the same brand of network cables for matching and use.
The main difference between Category 5e 8-core network cable and Category 6 network cable is transmission performance and bandwidth. Category 6 network cable supports higher transmission rate and bandwidth, and is suitable for 10 Gigabit Ethernet. Category 5e 8-core network cable is suitable for Gigabit Ethernet. When choosing, it should be selected according to specific needs and network environment.
