What Is PoE: Powering Cameras and APs over One Cable

PoE (Power over Ethernet) is a technology that delivers electrical power over the same twisted-pair cable as the data. A camera, access point or IP phone connects with a single cable — no power outlet or adapter needed next to the device.

Power comes from a PoE switch or injector, and the device simply works: power negotiation happens automatically and is safe for non-PoE devices.

There are three main standards: 802.3af (up to 15.4 W) — cameras and phones; 802.3at, also known as PoE+ (up to 30 W) — pan-tilt cameras and Wi-Fi 6 access points; 802.3bt, also known as PoE++ (up to 60–90 W) — PTZ cameras with heaters, video terminals, high-power access points.

Every standard reaches 100 meters over Cat5e/Cat6. Beyond that, use PoE extenders or fiber.

Every PoE switch has two limits: per-port power and the total budget. An 8-port switch with a 65 W budget cannot power eight 12 W cameras — that requires 96 W in total. This is the most common mistake in DIY equipment selection.

The rule: add up the rated power of all devices and allow a 25–30% margin — that gives you the minimum switch budget.

One cable instead of two runs (network + 220 V mains) means half the installation work and half the points of failure. Centralized power: a single UPS in the rack keeps all cameras running through a blackout. And a frozen camera can be rebooted remotely by cycling its PoE port — no site visit required.

That is why modern video surveillance systems are built almost exclusively on PoE.

A PoE injector is an "adapter" for a single device: a cheap way to power one camera from a regular switch. From three or four devices onward, a PoE switch pays off: fewer boxes, plus centralized monitoring and port management.

There are also devices that work the other way — PoE splitters, which extract power from the cable for devices without PoE support.

Besides the 802.3af/at/bt standards there is passive PoE: voltage goes into the cable with no negotiation with the device. Part of MikroTik and Ubiquiti gear is powered this way — but plugging a standards-based camera into a passive injector is risky: it may receive 24 V instead of the expected 48 V and fail to start or break.

The compatibility rule is simple: a standard PoE switch is safe for any device — before powering it interrogates the consumer and feeds nothing into a non-supporting port. Passive power is acceptable only as a pair of injector and device from one vendor at one voltage. In doubt — send us the models, we will check the specs.

PoE is the de facto standard for cameras, access points and IP phones: fewer cables, a central UPS, remote power management. The SAT Solutions catalog offers 4–48 port PoE switches, injectors and extenders in stock in Tashkent; we will help you calculate the power budget for your project.