Power over Ethernet (PoE) technology enables electrical power to be transmitted alongside data over standard Ethernet cables. It eliminates the need for separate power cables, simplifying the installation and management of networked devices.

PoE is commonly used in applications where it is inconvenient or impractical to run separate power lines to devices, such as Internet Protocol (IP) cameras, voice over IP (VoIP) phones, access points, and other networked equipment.

You may not know it, but you likely see PoE at work daily, that is, every time you use a VoIP phone for meetings.

Read More about Power over Ethernet

PoE’s basic idea is to deliver data and power over the same Ethernet cable. Instead of having separate power and Internet cables connected to PoE-enabled devices, therefore, you only have one.

What Are Some Key Features of Power over Ethernet?

Here are some key PoE features.

  • Power sourcing equipment (PSE): The device that injects power into the Ethernet cable, which can be a PoE-enabled network switch or a separate device known as a “PoE injector.”
  • Powered device (PD): The device that receives power from the Ethernet cable, such as an IP camera, a VoIP phone, a wireless access point (WAP), or any other compatible device.
  • Data and power transmission: PoE allows the simultaneous transmission of data and electrical power over the same Ethernet cable, typically using twisted-pair cables like Cat5e or Cat6.
  • Power levels: Different PoE standards support various power levels. IEEE 802.3af, for instance, provides up to 15.4 watts of power per port, while IEEE 802.3at (PoE+) delivers up to 30 watts. The latest standard, IEEE 802.3bt, also known as “PoE++,” “4PPoE,” or “802.3bt Type 4,” can provide up to 100 watts of power per port.
  • Auto-negotiation: PoE devices typically use a negotiation process to determine if both the PSE and PD support PoE. If they do, the PSE can provide power to the PD.

How Does Power over Ethernet Work?

PoE works via a negotiation process and the transmission of power and data between two main components—the PSE and the PD.

The PSE is responsible for injecting power into the Ethernet cable. It can be a PoE-enabled network switch or a PoE injector. The PSE detects if the PD is PoE-compatible.

The PD receives power and data from the Ethernet cable. Examples include IP cameras, VoIP phones, access points, and other networked equipment.

When a PD is connected to a PSE, a detection process begins to determine if the PD is PoE-compatible. The PSE sends a low-voltage test to the PD to check for a valid PoE signature. If the PD is PoE-compatible, it responds with the appropriate signature, and the PSE classifies the device based on its power requirements.

After detection and classification, a negotiation process takes place between the PSE and the PD to determine the power requirements and available power budget. This negotiation is based on the IEEE 802.3 standards and helps ensure that the PSE supplies the correct amount of power needed by the PD.

Once the negotiation is successful, the PSE delivers electrical power to the PD by modulating the power over the Ethernet cable. Power is typically transmitted over unused wire pairs in the Ethernet cable. The PD extracts the power from the Ethernet cable and uses it to operate, eliminating the need for a separate power source.

How Power over Ethernet Works

Watch this video to see PoE in action.

What Are Examples of Power over Ethernet-Compatible Devices?

Apart from IP cameras, VoIP phones, and access points, here are other examples of PoE-compatible devices.

  • Networked lighting systems: Some advanced lighting systems use PoE to power and control networked LED lights, allowing centralized management and control.
  • Smart displays and signage: Digital signage and smart displays often use PoE for data connectivity and power, enabling flexible placement without needing electrical outlets.
  • Networked audio systems: PoE is used in specific audio systems, such as networked speakers and amplifiers, to simplify cabling and installation.
  • Point-of-sale (PoS) systems: Some PoS devices, such as card readers and barcode scanners, may utilize PoE for power and data connectivity.
  • Biometric access control systems: Devices like fingerprint scanners and facial recognition systems in access control setups may leverage PoE for power and communication.
  • Videoconferencing equipment: Certain videoconferencing cameras, microphones, and other peripherals can be powered using PoE.
  • Smart building technologies: PoE is increasingly integrated into various smart building technologies, including sensors, controllers, and other Internet of Things (IoT) devices.
  • Networked printers: Some networked printers support PoE, simplifying their installation and placement within an office environment.
  • Intercom systems: PoE is used in modern intercom systems, allowing audio and video communication to be integrated over a single Ethernet cable.

PoE enhances flexibility, reduces cable clutter, and streamlines the deployment of PoE-compatible devices in various settings. As the technology continues to evolve, more devices across different domains will likely adopt the technology for power and data connectivity.

Key Takeaways