Understanding Power over Ethernet (PoE) in Network Switches

Power over Ethernet (PoE) is a smart way to send electric power and internet data through the same Ethernet cable.

PoE icon

Normally, a device needs:

One cable for internet
One cable for power

With PoE, you only need one cable. That’s it. One cable does both jobs.

Why does it exist?

PoE makes life easier because:

You don’t need a nearby wall outlet
Fewer cables = less mess
Devices can be placed almost anywhere
Setup is faster and cleaner

Think of PoE as a two-in-one cable: Internet + Power.

What does a PoE network switch do?

A PoE network switch is like a power-giving internet distributor.

An example of a PoE switch

It:

Sends internet data to devices
Sends power to devices
Does both at the same time
Uses regular Ethernet cables

If a device supports PoE, the switch knows and safely sends power. If it does not, no power is sent, so nothing gets fried.

Imagine this:

You want to install a security camera on a high wall outside your home.

Without PoE:

You need an outlet nearby
You might drill more holes
You deal with messy wiring.

With PoE:

One ethernet cable from the PoE switch (PSE)
Camera gets power + internet
Cleaner, safer, and easier

PoE is popular because it is:

Efficient
Safer than DIY power wiring
Easier to maintain
Great for homes, offices, and businesses

In short, PoE turns your network cable into a power cable, and the PSE supplies that power.

What is Power Sourcing Equipment (PSE)?

PSE stands for Power Sourcing Equipment. This is just a fancy name for the device that provides power in a PoE setup. In simple terms, the PSE is the power giver.

Common PSE examples:

A PoE network switch (most common)
A PoE injector (used when the switch has no PoE)

A PoE injector

The PSE is smart. Before sending power, it:

Checks if the connected device actually supports PoE
Sends only the amount of power needed
Stops power if the device does not need it

That’s why PoE is safe even for regular non-PoE devices.

What is Active versus Passive PoE?

Active PoE follows recognized technical standards such as:

IEEE 802.3af
IEEE 802.3at
IEEE 802.3bt

Its key characteristics are:

Checks if the connected device supports PoE before sending power
Automatically adjusts to the device’s required power level
Designed with built-in protection to prevent damage

Best suited for: Modern offices, homes, and professional installations where safety and compatibility are priorities.

Passive PoE, on the other hand, does not follow IEEE negotiation standards.

Its key characteristics are:

Sends power immediately without checking compatibility
Delivers fixed voltage
Requires exact voltage matching between the power source and the device

Best suited for: Specific devices that clearly state they require Passive PoE.

If you are unsure, it is recommended to choose Active (IEEE-standard) PoE. It significantly reduces the risk of equipment damage, and it is compatible with most current networking devices.

What is a Powered Device (PD)?

A Powered Device (PD) is any device that receives electrical power through a network cable using PoE. It does not generate or send power. It only receives and uses power supplied through the ethernet cable.

In the PoE setup below, the IP security camera is the equipment being powered, not the one supplying power.

A PD device illustration

Other common examples for PD are:

Wireless access points
VoIP desk phones
Some network intercoms
Certain smart lighting or IoT devices

Common things that use PoE

Here are everyday examples you’ll actually see:

Security Cameras

Instead of running:

One cable for video
One cable for power

PoE cameras use one cable only. Clean, simple, and professional.

WiFi Access Points

Ever wonder how those WiFi boxes on the ceilings of cafes and schools get power? Most use PoE, so they don’t need a bulky power outlet installed on the ceiling.

IP Phones

Office phones can run entirely on PoE. Even if the power goes out, the phone may still work if the switch has a backup power source.

Door Access Systems

Keycard or fingerprint scanners near doors often use PoE because outlets near doors are awkward.

A guide to PoE Standards

There are three main “strengths” to PoE:

1. Standard PoE (Basic Level): 802.3af

This provides a small amount of power (up to 15.4W).

Best for: Simple gadgets that stay "awake" all day, like basic desk phones or simple home security cameras.

2. PoE+ (Middle Level): 802.3at

This provides double the power (up to 30W).

Best for: Devices that do more work, such as powerful WiFi routers or cameras that can physically rotate and zoom in.

3. PoE++ ("Super" Level)

a. 802.3bt Type 3 or PoE++/UPoE

Type 3: Delivers up to 60W.

Best for:

High-performance Wi-Fi® 6 or Wi-Fi® 6E Access Points
Motorized, outdoor-rated PTZ (Pan-Tilt-Zoom) security cameras with built-in heaters/wipers
Video conferencing systems and integrated A/V equipment
Point-of-Sale (POS) kiosks and digital signage controllers

b. 802.3bt Type 4 or UPoE+

Type 4: Delivers up to 90W-100W.

Best for:

Next-generation Wi-Fi® 7 access points
PoE-powered LED lighting systems (smart lighting infrastructure)
Mini-PCs and compact desktop computers
Large, interactive touch panel displays and control panels
Industrial sensors and controllers that require robust power

All that means is:

More plus signs = more power available

Basic devices need basic PoE. Big devices like advanced cameras need PoE+ or PoE++.