Power over Ethernet lets a single cable carry both data and electrical power to IP cameras, wireless access points, VoIP phones, and IoT sensors. Not all PoE is equal — choosing the wrong standard means underpowered devices or wasted budget.
The Three PoE Standards
- IEEE 802.3af (PoE) — 15.4 W at the port, 12.95 W at the device. Basic IP cameras and VoIP phones.
- IEEE 802.3at (PoE+) — 30 W at the port, 25.5 W at the device. Wi-Fi 6 APs and PTZ cameras.
- IEEE 802.3bt (PoE++) — Type 3: 60 W; Type 4: 90 W. Wi-Fi 6E/7 APs, thin clients, LED systems.
Power Budget Planning
A 24-port PoE+ switch does not deliver 30 W on all ports simultaneously — it has a shared power budget (typically 185–740 W). Sum all device wattages, add 20% headroom, and size your switch accordingly.
Cable Requirements for PoE
PoE++ (802.3bt) uses all four conductor pairs and demands low DC resistance. Cat6 and Cat6A are the correct choice. Avoid 28 AWG patch cords for high-power runs. Maximum cable length: 100 m.
Frequently Asked Questions
Can a PoE device plug into a PoE+ switch?
Yes — all PoE standards are backwards compatible. The switch negotiates and delivers only what the powered device requests via the IEEE detection handshake.
Does PoE harm non-PoE devices?
No. A device that does not respond to the PoE signature never receives power down the cable.
Is Cat6 required for PoE?
Cat6 and Cat6A are strongly recommended for PoE++ because of lower DC resistance and better thermal performance under sustained high-current loads. DAD LINK Cat6 and Cat6A cables are tested to TIA-568 and ISO/IEC 11801 standards.