PoE

networking

Power over Ethernet: the switch feeds power down the data cable, so phones, cameras, and access points need no outlet.

IEEE 802.3af/at/bt tiers roughly 15 W, 30 W, and up to 90 W per port.

Power over Ethernet delivers power and data on one cable, which is the entire reason cameras, access points and phones can be installed where there is no socket. The budget is what determines whether a design works: each standard defines power at the source, the cable loses some of it, and what matters is what remains at the device.

The failures are almost always budget or heat. A switch rated for a total power draw across all ports cannot supply every port at maximum simultaneously, so a full rack of high-draw devices exceeds a figure nobody checked. Bundled cable carrying power in a warm conduit derates further, and a device that boots and then reboots under load is usually short of power rather than faulty.

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