Power over Ethernet (PoE) provides DC electrical power to Ethernet devices using a copper twisted pair within the Ethernet cable. This eliminates separate power cables in many installations, saving the cable cost and installation requirements.
PoE makes use of spare twisted pairs within the Ethernet cable. For Cat 5e and 6, there are two data pairs and two spare pairs made from the eight wires. A DC voltage between 44 and 57 volts is used, with 48 volts typical.
The Type 1 version of PoE provides up to 15 watts of power using a single twisted pair. PoE+ or Type 2 increases power to 30 watts using both spare pairs. PoE++ or 4PPoE uses all four pairs to handle the additional power, with Type 3 at 60 watts and Type 4 at 100 watts.
Power over Ethernet offers several advantages over running separate power cables. It eliminates the need for a separate power cable, reducing installation costs and time. It also provides enhanced flexibility by locating Ethernet devices away from a power source. Plus, a single power source can more easily be backed up by an uninterruptible power supply rather than relying on distributed wall adapters.
Among many applications, PoE is used for VoIP phones, networked surveillance cameras, wifi routers, RFID readers, intercoms, LED lighting, and many other smart home or business premises applications.