802.3af

The 802.3af Power over Ethernet (PoE) standard, also known as Type 1, was ratified by the Institute of Electrical and Electronics Engineers (IEEE) in 2003. This standard allows for delivery of electrical power, along with data, to network devices over Ethernet cabling. Under the 802.3af standard, power sourcing equipment (PSE) can supply a maximum of 15.4 watts of power per port. However, due to power dissipation in the cable, only 12.95 watts are assured to be available at the powered device (PD). This standard supports 10BASE-T and 100BASE-TX, but it can also be used with 1000BASE-T by using all four pairs in the Category 5 cable. The 802.3af standard uses an automatic detection process to ensure power is only supplied if a valid PoE device is connected. This makes it safe for devices not compatible with PoE. The 802.3af standard has been largely superseded by the more powerful 802.3at (Type 2 or PoE+) and 802.3bt (Type 3 and 4 or PoE++/UPoE) standards, but it remains in use in many legacy installations.