Power over Ethernet (PoE)

also: PoE · PoE+ · 802.3af · 802.3at · 802.3bt

Delivering DC power and data over one Ethernet cable under IEEE 802.3 standards, so cameras, access points and sensors need no separate supply.

The power sourcing equipment (a PoE switch or injector) supplies power over the Ethernet cable, and the powered device negotiates how much it needs. IEEE 802.3af (Type 1) provides about 15.4 W at the source; 802.3at (Type 2, "PoE+") 30 W; and 802.3bt adds Type 3 (60 W) and Type 4 (90 W) at the source. Less is available at the device because of cable losses.

PoE suits fixed installations such as cameras, access points, displays, access control, building sensors and controllers. It avoids separate power wiring and makes central backup power easy.

Where it bites: isolation requirements, heat in the powered device's converter, the power class and total power budget customers' switches can actually supply, and standard Ethernet cable-length limits.

Founder takeaway

Choose the lowest PoE class that meets peak demand, and confirm customers' switches can supply it on all ports at once.

engineer review pending