PoE Standards:

24 Volt Passive

A cost effective standard used mostly by ISP's and Wireless Access Points.  The major manufacturers are: Ubiquiti, Mikrotik, and OpenMesh

24 volt Mode B (pins 4,5 and 7,8) Passive PoE - Either 10/100 or gigabit

IEEE 802.3af

Pronounced "eye triple E" 802 "point" 3 A-F.  Most frequently what people mean when they just say "POE", check out this video.

44-56 volt Mode A or B providing up to 15.4 watts at the Power Sourcing Equipment (PSE) and 12.9 watts at the Powered Device (PD).  Strictly speaking compliant 802.3af also has a auto-negotiating function, however most PD's work with 802.3af compatible PoE, meaning a Passive PSE.

IEEE 802.3at

Pronounced the same way with the A-T.  Also known as PoE+.

44-56 volt Mode A or B providing up to 25.5 watts at the Power Sourcing Equipment (PSE).  Strictly speaking compliant 802.3at also has a auto-negotiating function, however most PD's work with 802.3at compatible PoE, meaning a Passive PSE.  Cisco and Meraki 802.3at wireless access points require the auto-negotiation.

 

Important Terms:

10/100

Also called "Fast Ethernet", 10/100 devices transmit data at a maximum rate of 100 megabits per second. All PoE cameras are compatible with 10/100 PoE Injectors. Many IP phones and WiFi Access Points can also be used with 10/100 PoE Injectors, but others require the faster Gigabit data rate.
1000BASE-T 1000Base-T refers to the IEEE standard for Gigabit Ethernet over copper wiring. Unlike 10/100 or Fast Ethernet, all four wire pairs of the Cat 5 (or better) cable are used for data under the 1000Base-T standard, so PoE power and data share the same wires.
12V, PoE Technical spec listed on many PoE devices, including PoE cameras. "12v, PoE" means the device operates at 12 volts when plugged in at the wall but at a higher voltage with Power over Ethernet. These devices need 48 volts when powered by Passive PoE.
802.3af 802.3af is the first Power over Ethernet IEEE standard. In 802.3af, a minimum of 44 volts DC is required with up to 12.95 watts available for the powered device (cameras, phones, etc.) Our passive PoE devices use 48 volt DC power supplies to power standard 802.3af devices.
802.3at 802.3at is the IEEE Power over Ethernet standard for high powered devices (up to 25.5 watts). For Passive PoE, 56 volts of power is transmitted on all four pairs of the Cat 5 (or better) Ethernet cable.
AC Alternating Current. Alternating Current is more efficient than DC (Direct Current) at high voltages, so AC power is used to deliver electricity to homes and businesses then converted to DC (Direct Current) for powering electronics.
Amperage Unit of measure for electric current. Amperage multiplied by voltage equals wattage.
CAT-5 Cat 5 (short for Category 5) cable, carries data for both 10/100 and Gigabit Ethernet. The cable consists of four or more pairs of wires, with each pair twisted together at differening intervals to reduce interference from the other pairs. Data can be run to a maximum of 100 meters over Cat 5. Past that, a repeater or network switch is required to continue the signal. Cat 5e and Cat 6 cables are similar to Cat 5 but follow improved specifications.
Current The flow of an electric charge. Wattage measures the electric current available.
DC Direct Current. In Direct Current, the electrical charge flows in one direction, as opposed to Alternating Current. DC Power Supplies convert AC power from "the wall" to DC power for electronic devices. Passive PoE injectors use DC power.
Ethernet Ethernet refers to the standard technologies used in Local Area Networks (LANs). The most familiar Ethernet component for most people is the Ethernet cable (see Cat 5).
Gigabit Gigabit devices transmit data over Ethernet at a rate of one gigabit per second. Many IP phones and WiFi Access Points transmit data at Gigabit rates, while PoE cameras do not. Gigabit data uses all four pairs of wire in the Ethernet cable, and Gigabit capable devices require a Gigabit capable PoE Injector or Switch to operate properly.
IEEE The Institute of Electrical and Electronics Engineers, an organization for technical professionals. Through its Standards Association, a community of technical experts from the IEEE develop global standards for a wide variety of fields, including Power over Ethernet.
Mode A Mode A refers to Power over Ethernet that is added to the wire pairs 1,2 and 3,6 of a standard Cat 5 cable. Mode A is commonly used to power 802.3af (48 volt) devices.
Mode B Mode B refers to Power over Ethernet that is added to the wire pairs 4,5 and 7,8 of a standard Cat 5 cable. Mode B is used with PoE devices that require 24 volts to operate. According to the IEEE standard, 802.3af (48v) PoE devices should also be compatible with Mode B.
Passive PoE Power over Ethernet in which the PoE injector provides power at all times rather than negotiating power needs with the camera, phone, or other device.
Pinout The arrangment pins (contacts) in an electrical circuit. In Power over Ethernet, the pinout refers to the wire pairs used to transmit power over Cat 5 (or better) cables (see Mode A and Mode B).
PoE Injector Also referred to as a midspan, a PoE Injector sits between a switch and a powered device. It adds electrical power to an Ethernet cable but does not manage data. Because of this, each port must have a data line in for every PoE/Data line out.
PoE Switch A network switch with a built-in PoE injector. Unlike a simple PoE injector, a PoE switch can route network traffic to the powered devices, meaning only one data line in is required for all Data/PoE lines out.
Voltage Unit of measure for the difference in electrical potential for two points in a circuit. Voltage greater than the amount specified will damage an electronic device.
Wall Wart The power plug usually included with electronics. Usually a black, square box with a DC power cable attached, wall wart plugs are notorious for taking up excessive space on power strips and wall outlets.
Wattage The unit of measure for the rate of electrical transfer in a circuit. The maximum wattage available from a power source should be greater than the maximum wattage required by the powered device. A PoE camera requiring 10 watts of power needs a power supply of 10 or more watts, and there is no danger of damaging a device with "excess wattage."