What Is a PoE Switching Hub?
A PoE switching hub is a switching hub with the ability to supply power through its Ethernet ports.
PoE stands for “Power over Ethernet” and refers to the ability to supply power to powered devices via Ethernet cables (so-called LAN cables), and is used by connecting devices that support the POE standard to each other via Ethernet cables.
A switching hub is a device that efficiently relays a network when multiple computers communicate with each other, using the Ethernet communication standard and relaying computer traffic through an Ethernet port.
Switching hubs were introduced in the 1990s. At that time, 10 Gbps was the typical network speed, but today, the speed has increased to 100 Gbps or even higher, and switching hubs are now available that support this speed.
Uses of PoE Switching Hubs
PoE switching hubs are used on networks with Ethernet communications. The following is an example of a device connected to a PoE switching hub:
- IP phones and network cameras
- Wi-Fi Access Point
- Lighting equipment
- Switching hub
PoE-compliant receiver devices are suitable for devices located in remote areas because they do not require power cables. Therefore, they are often used for surveillance cameras and the like.
Note, however, that different POE switching hubs have different specifications in terms of the number of devices that can be powered and power supply capacity.
Principle of PoE Switching Hubs
A PoE switching hub is a device that has both POE and switching hub functions. The respective functions are as follows:
1. PoE Function
The PoE function is a function that uses LAN cable wiring to supply power; a LAN cable is a group of two 4-pair thin core cables.
For communications at 100 Mbps or lower, only two pairs are used, one for transmitting and the other for receiving, but for communications at 1 Gbps or higher, all four pairs are used. There are two types of power supply methods: TypeA and TypeB.
Type A is a method in which the communication line and power supply line are shared, and is used for communications at 1 Gbps or faster, while Type B is a method in which power is supplied using two pairs, which are not used for communications at 100 Mbps or slower.
2. Switching Hub Function
A switching hub is a feature that efficiently relays Ethernet communications. Although just a hub also has a relay function, it has the characteristic of retransmitting incoming communication data to all connected devices.
This has the disadvantage that the network tends to become congested because the data reaches other devices than the one it is communicating with. In contrast, switching hubs use MAC addresses, which are unique addresses of devices, to identify the devices with which they should communicate. Since data is sent only to the necessary devices, signals can be relayed efficiently.
Additional Information on PoE Switching Hubs
1. PoE Standards
PoE was defined as a standard by the Institute of Electrical and Electronics Engineers (IEEE), an American standards organization. The standardization of PoE enables connection even when the manufacturers of the devices receiving and receiving power are different from each other.
IEEE802.3af is a slightly older standard, and IEEE802.3at was developed to support a higher power output. Recently, PoE switching hubs are increasingly supporting PoE+.
PoE is divided into classes from 0 to 8 according to the power supplied, and the larger the class, the higher the power supply capacity. The larger the class, the higher the power supply capacity. The largest class, Class 8, is defined as 90 W for power supply and 73 W for power reception.
2. Pass-Through of PoE Switching Hubs
A PoE switching hub that supports PoE power receiving is available. This product can transmit power from a PoE powered device to a PoE powered device. This function is called pass-through.
Normally, the maximum distance for PoE is defined as 100 m, but pass through makes it possible to achieve a total transmission distance of 200 m. This function is useful in large factories.
When using pass-through, it is necessary to design the system so that the maximum total power is not exceeded; the amount of power available for PoE is not large, so connecting numerous devices to a PoE switching hub can easily exceed the maximum amount of power.