PoE

PoE (Power over Ethernet) is a network access layer technology that supplies DC power over Ethernet cables so both data and power travel on the same twisted-pair cable. It is standardized in IEEE 802.3af/at/bt and includes detection and classification phases to ensure only compatible devices receive power, with different power classes depending on the standard. For Audio/Video (e.g., IP cameras, networked speakers, Dante interfaces), Maker projects (e.g., Raspberry Pi or microcontroller boards with PoE HATs), and Web/network equipment (e.g., Wi‑Fi access points, edge devices), PoE reduces the need for separate power supplies and simplifies deployments. Practical constraints include cable category (Cat5e or better), the ~100 m Ethernet distance limit, the power budget of the switch or injector, and the difference between standard (active) PoE and some passive PoE solutions.

Imagine setting up a classroom or small studio: a managed PoE switch powers IP cameras (Audio/Video), two ceiling network speakers, and a Wi‑Fi access point (Web). For a maker project you plug a Raspberry Pi with a PoE HAT into the same switch so it can send sensor data to a web dashboard without needing a separate power adapter. During installation you check the switch's power budget and use Cat5e/Cat6 cables to limit voltage drop and distance issues; for critical AV gear you prefer ports that support 802.3at/802.3bt. You can also use a PoE injector for a single device and use LLDP or SNMP via the switch's web interface to monitor how much power each device is drawing.