Power over Ethernet (PoE) has transformed modern networking by allowing a single Ethernet cable to carry both data and DC power.
From surveillance cameras to wireless access points, thousands of devices now rely on PoE for simplified installations and reduced wiring costs.
At the heart of every PoE system are two essential components:
Understanding how PSE and PD interact is crucial for designing reliable PoE networks, ensuring power compatibility, and selecting the right PoE RJ45 connectors and magnetics.
PSE is the power-providing end of a PoE link. It delivers electrical power along the Ethernet cable to downstream devices.
| PSE Type | IEEE Standard | Max Power Output (per port) | Pairs Used | Typical Applications |
|---|---|---|---|---|
| Type 1 | IEEE 802.3af | 15.4 W | 2 pairs | IP phones, basic cameras |
| Type 2 | IEEE 802.3at (PoE+) | 30 W | 2 pairs | Access points, thin clients |
| Type 3 | IEEE 802.3bt (PoE++) | 60 W | 4 pairs | PTZ cameras, digital signage |
| Type 4 | IEEE 802.3bt | 90–100 W | 4 pairs | Industrial switches, LED lighting |
A Powered Device (PD) is any network device that receives power from the PSE through the Ethernet cable. The PD extracts DC voltage from the cable pairs using internal magnetics and power circuits.
Each PD communicates its required power level using classification signatures or LLDP negotiation, enabling the PSE to allocate the correct wattage.
| PD Class | IEEE Type | Typical Power Draw | Common Devices |
|---|---|---|---|
| Class 0–3 | 802.3af (PoE) | 3–13 W | IP phones, small sensors |
| Class 4 | 802.3at (PoE+) | 25.5 W | Dual-band WAPs |
| Class 5–6 | 802.3bt (PoE++) | 45–60 W | PTZ cameras |
| Class 7–8 | 802.3bt (PoE++) | 70–90 W | LED panels, mini PCs |
In a PoE network, the PSE provides power while the PD consumes it.
Before sending power, the PSE first performs a detection phase — checking if the connected device has the correct 25kΩ signature.
If valid, power is applied, and data transmission continues simultaneously over the same pairs.
| Function | PSE (Power Sourcing Equipment) | PD (Powered Device) |
|---|---|---|
| Role | Supplies DC power over Ethernet | Receives and converts power |
| Direction | Source | Sink |
| Power Range | 15 W – 100 W | 3 W – 90 W |
| Standard | IEEE 802.3af / at / bt | IEEE 802.3af / at / bt |
| Example Device | PoE switch, injector | IP camera, AP, phone |
This handshake ensures interoperability between devices from different manufacturers — a key strength of IEEE PoE standards.
| Feature | Endspan PSE | Midspan PSE |
|---|---|---|
| Integration | Built into network switches | Standalone injector between the switch and the PD |
| Data Path | Handles both data & power | Adds power only, data bypasses |
| Deployment | New PoE-enabled switch installations | Upgrading non-PoE switches |
| Cost | Higher initial cost | Lower upgrade cost |
| Latency | Slightly lower (one device fewer) | Negligible but slightly higher |
| Example | PoE switch (24-port) | Single-port PoE injector |
Both types comply with IEEE 802.3 standards and can coexist in the same network as long as they follow the detection and classification process.
High-performance PoE systems require components that can safely handle current and maintain signal integrity.
LINK-PP provides PoE RJ45 connectors with integrated magnetics, optimized for IEEE 802.3af / at / bt compliance.
Each connector ensures:
LINK-PP PoE connectors guarantee long-term reliability for both Endspan and Midspan PSE designs, ensuring safe and efficient power transmission.
Q1: Can any Ethernet port provide PoE?
Only if the device is a certified PSE (e.g., PoE switch or injector), standard non-PoE ports do not supply power.
Q2: Can a device be both PSE and PD?
Yes. Some network devices, such as daisy-chainable access points or PoE extenders, can function as both.
Q3: Is PoE power safe for network cables?
Yes. IEEE standards limit voltage and current per pair to safe levels. For PoE++, use Cat6 or higher to reduce heating.
In PoE networks, understanding the roles of PSE and PD is fundamental to achieving reliable power delivery and efficient design.
Whether the power originates from an Endspan switch or a Midspan injector, IEEE standards ensure safe, intelligent, and interoperable operation.
By integrating high-quality LINK-PP PoE RJ45 connectors, designers can guarantee consistent power transmission, signal integrity, and long service life — the foundation for modern smart network infrastructure.
→ Explore LINK-PP’s full line of PoE RJ45 connectors for PSE and PD applications.
