| Table of Contents What Is PoE and Why Is It Useful? What Does an Ethernet Cable Look Like Inside? How Did PoE Work in the Past? Modern PoE: Using All Four Pairs |
Have you ever wondered how a small network camera or a wireless access point can work without being plugged into a wall outlet? It seems like magic, but it’s actually a smart technology called Power over Ethernet, or PoE for short.
In this article, we will explore a very common question: Which wires carry power in PoE? We’ll break it down into simple parts, look at different types of network cables, and explain how electricity and data travel together to make our devices work.
What Is PoE and Why Is It Useful?
Let’s start with the basics. PoE is a technology that allows us to send both data (like videos, emails, or web pages) and electrical power through the same network cable. Normally, a device like a security camera needs two connections: one for the internet and one for power. With PoE, you only need one cable.
This is super useful because it saves money on extra wires and power outlets. It also makes installation easier and more flexible. You can place a Wi-Fi access point on a high ceiling or an IP camera in a far corner of a building without needing an electrician to install a new power socket.
What Does an Ethernet Cable Look Like Inside?
To understand which wires carry power, we first need to look inside a standard network cable, like a Cat5e or Cat6 cable. These cables are often called Ethernet cables or CATx cables.
Inside the plastic coating, you will find eight smaller wires twisted together in four pairs. Each pair is color-coded. The standard colors are:
· Pair 1: Blue and White/Blue
· Pair 2: Orange and White/Orange
· Pair 3: Green and White/Green
· Pair 4: Brown and White/Brown
These eight wires connect to eight metal pins inside an RJ45 connector (the plastic plug at the end of the cable). Each pin has a number, from 1 to 8.
How Did PoE Work in the Past?
In the early days of PoE, the technology was simpler but also more limited. Engineers used only two of the four twisted pairs to carry electricity. The other two pairs were only used for data transmission.
In that older setup, the power traveled through the same wires that were used for data. For example, Pair 2 (pins 1 and 2) and Pair 3 (pins 3 and 6) carried both data and power. The remaining pairs (blue and brown) were unused or carried only data.
This method worked fine for low-power devices, but it had a problem: interference. Because data and power travel at different frequencies, sending them together on the same wire could sometimes cause noise or signal loss.
Modern PoE: Using All Four Pairs
Today, PoE technology has improved a lot. Newer standards, like IEEE 802.3bt (also called PoE++ or 4PPoE), allow us to use all four twisted pairs to carry power. This is a big deal because it increases the amount of power that can be sent to a device.
But wait — doesn’t that cause more interference? Actually, no. Modern PoE sends data and power together on the same wires. Because data and power use different frequency ranges, they don’t interfere with each other. In fact, using the same pair for both reduces interference compared to the old method.
So, in modern PoE systems, all eight wires can carry power. But the exact wires used depend on two things: the speed of your network (100 Mbps or 1000 Mbps) and the PoE standard (af, at, or bt).
Final Thoughts
So, which wires carry power in PoE? The answer depends on your network speed and the PoE standard you are using.
· In 100 Mbps networks, power can travel on pins 1,2,3,6 (Mode A) or on pins 4,5,7,8 (Mode B).
· In 1000 Mbps (Gigabit) networks, all eight wires carry power.
· In modern high-power PoE standards like 802.3bt, all four pairs are used to deliver maximum power.
Understanding this helps you choose the right cables, avoid overheating, and build a reliable network. Whether you are setting up a small home office or a large building full of cameras and access points, knowing how PoE switch works will save you time, money, and headaches.
If you’re looking for a powerful, reliable, and easy-to-manage solution, the 10-Port Gigabit Managed Industrial PoE Switch is a great choice. This industrial PoE switch supports up to 8 PoE devices, works in extreme temperatures (-40°C to 75°C), and gives you the tools to keep your network safe and fast.
Now that you know which wires do the job, you can look at an Ethernet cable with a little more respect. It’s not just a data cable — it’s also a power line in disguise.