Power over Ethernet (PoE) technology enables the transmission of both data and DC power through a single Ethernet cable, simplifying network infrastructure for devices such as IP cameras, wireless access points (WAPs), VoIP phones, and industrial controllers.
The three primary IEEE standards defining PoE are:
Understanding their differences in power levels, wiring modes, and compatibility is crucial when designing or selecting PoE equipment.
| Standard | Common Name | PSE Power Output | PD Power Available | Pairs Used | Typical Applications |
|---|---|---|---|---|---|
| IEEE 802.3af | PoE (Type 1) | 15.4 W | 12.95 W | 2 pairs | IP phones, basic cameras |
| IEEE 802.3at | PoE+ (Type 2) | 30 W | 25.5 W | 2 pairs | Wireless APs, video terminals |
| IEEE 802.3bt | PoE++ (Type 3) | 60 W | ~51 W | 4 pairs | PTZ cameras, smart displays |
| IEEE 802.3bt | PoE++ (Type 4) | 90–100 W | ~71.3 W | 4 pairs | LED lighting, mini-switches, and laptops |
Note: IEEE specifies the power available at the Powered Device (PD), while vendors often quote the PSE output. Cable length and category affect actual delivered power.
PoE power is transmitted using center-tapped transformers inside Ethernet magnetics.
Gigabit Ethernet and higher (1000BASE-T and beyond) inherently use all four pairs, allowing seamless 4PPoE operation.
Each PoE-compliant device is categorized by power class and detected by the Power Sourcing Equipment (PSE) through a resistance signature.
Modern PoE+ and PoE++ devices also use LLDP (Link Layer Discovery Protocol) for dynamic power negotiation, allowing smart switches to allocate power efficiently.
For example, a managed PoE switch may assign 30 W to a camera and 60 W to an access point, ensuring optimal power budgeting across all ports.
Q1: What’s the difference between PoE, PoE+, and PoE++?
PoE (802.3af) delivers up to 15.4 W per port, PoE+ (802.3at) increases that to 30 W, and PoE++ (802.3bt) provides up to 90–100 W using all four wire pairs.
Q2: Do I need special cables for PoE++?
Yes. Cat6 or higher cables are recommended to handle higher currents and maintain thermal performance over long runs.
Q3: Can PoE damage non-PoE devices?
No. IEEE-compliant PSEs perform detection before applying voltage, ensuring non-PoE devices are not powered accidentally.
| Application | Typical Power | Recommended PoE Standard | Example Device |
|---|---|---|---|
| VoIP phones | 7–10 W | 802.3af | Office IP phone |
| Wi-Fi 6 access point | 25–30 W | 802.3at | Enterprise AP |
| PTZ security camera | 40–60 W | 802.3bt Type 3 | Outdoor surveillance |
| Industrial IoT controller | 60–90 W | 802.3bt Type 4 | Smart factory node |
As PoE power levels rise, connector quality and magnetics design become critical.
LINK-PP offers a full range of RJ45 connectors optimized for PoE/PoE+/PoE++ applications:
Each model features:
LINK-PP PoE Magjacks ensure safe, efficient power delivery for both endspan and midspan PSE designs, making them reliable choices for modern PoE networks.
From the original 15W PoE standard to today’s 100W PoE++ networks, Power over Ethernet continues to simplify power delivery for connected devices.
Understanding IEEE 802.3af, 802.3at, and 802.3bt ensures compatibility, efficiency, and safety in every deployment.
For OEMs, system integrators, and network installers, choosing LINK-PP PoE RJ45 connectors guarantees long-term performance and compliance with the latest PoE technologies.
→ Explore LINK-PP’s full range of PoE-ready RJ45 connectors for your next project.
