A PoE switch is powered by an internal or external power supply that provides DC electricity to the switch itself, which it then distributes to connected PoE-enabled devices over Ethernet cables.

Powering the Switch Itself

A PoE switch requires its own electrical power to operate, just like any standard network switch. This power typically comes from:

• Internal AC-to-DC power supply: Most PoE switches have built-in power supplies that plug into a standard electrical outlet, converting AC mains power to the DC voltage needed for the switch's circuitry and PoE output .
• External power source: Some smaller or specialized PoE switches may rely on external power adapters or injectors to supply the necessary DC power .
• UPS (Uninterruptible Power Supply): For critical applications, a PoE switch can be connected to a UPS to maintain operation during power outages, ensuring connected devices like cameras or access points remain powered .

Delivering Power to Connected Devices

Once the switch itself is powered, it can provide electricity to PoE-enabled devices (PDs) over the same Ethernet cables used for data transmission. This is achieved through:

• Power Sourcing Equipment (PSE): The switch acts as a PSE, injecting DC power into the Ethernet cable according to IEEE standards (802.3af, 802.3at, or 802.3bt) depending on the device's power requirements .
• PoE Standards: Original PoE (802.3af) delivers up to 15.4 W per port, PoE+ (802.3at) up to 30 W, and PoE++ (802.3bt) can provide up to 100 W per port for high-power devices .
• PoE Passthrough: Some switches can receive power from an upstream PoE source and pass it along to other devices, using a portion of the power for their own operation and the remainder for connected devices .

Summary

In essence, a PoE switch is powered like a regular network switch via an internal or external power supply. It then distributes power to connected PoE devices over Ethernet cables, combining data and electrical power in a single connection. This setup simplifies installations, reduces cabling, and allows devices to be placed where traditional power outlets may not be available .