What is Power Over Ethernet? PoE Explained

Power over ethernet (PoE) was invented by PowerDsine in 1997, the first PoE injector was installed in 1998.

PoE encompass any systems or devices that transmit or receive both power and data via twisted pair ethernet cabling. The oldest PoE standard readily found in the wild, also known as standard PoE, is IEEE 802.3af, which was introduced in 2003. It has the capability of supplying 44-57 volts with a current of 10-350mA, which means the maximum power draw of a device on a single standard PoE port is 15.4W.  that works out to about 13W to the devices, which is enough to run access points and fixed security cameras but, not higher power devices like point of sale (PoS) systems or thin clients. It’s very alluring to not have to hire an electrician to install power points for remote cameras or ceiling mounted access points.

The second of the 3 types of PoE are IEEE 802.3at also known as PoE +, this was introduced as PoE devices started needing more power as they introduced new features, such as pan and tilt security cameras and high-power access points. PoE+ can deliver 25 Watts of power to supported devices.

For the last PoE standard you have PoE ++ or IEEE 802.3bt (type 3) and IEEE 802.3bt (type 4). To carry the 51W and 71.3W of power to the device POE ++ type 3 and 4 respectively can deliver, how the power and data are carried had to be changed. For standard PoE and PoE +, 2 of the 4 pairs of twisted conductors in an ethernet cable are used for power, while the remaining 2 pairs are used to carry the data signal. With PoE ++ all 4 pairs of conductors are used to carry both the power and data for the device. This is done by transmitting the power and data at different electrical frequencies.

Whether you need to power your camera systems, VoIP phones, alarm system or access points, PoE has you covered.

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