Power over Ethernet

Power over Ethernet (also referred to as PoE or Power over LAN) is a technology that integrates power into a standard LAN infrastructure. It enables power to be provided to the network device, such as an IP phone or a network camera, using the same cable as that used for network connection.

Power over Ethernet is especially suited for IP-Surveillance and remote monitoring applications because it eliminates the need for a power outlet at the camera location -- particularly in places previously thought of as impractical or too expensive to connect to a power outlet. This makes installation easier and cheaper since there is no need for separate power and data cable infrastructure and costly AC outlets. In addition, an electrician does not need to be involved.

Another benefit of Power over Ethernet is the UPS function. Many companies have their network switches connected to a UPS (Uninterrupted Power Supply) device. Since the Power over Ethernet hubs are connected to the network switches, the cameras and video servers can continue to function even in the case of a power shortage.

PoE technology is regulated in a standard called IEEE 802.3af and is designed in a way that does not degrade the network data communication performance or decrease the network reach. The power delivered over the LAN infrastructure is automatically activated when a compatible terminal is identified, and blocked to legacy devices that are not compatible. This feature allows users to freely and safely mix legacy and PoE-compatible devices, on their network.

The standard provides power up to 15.4W on the switch or midspan side, which translates to a maximum power consumption of 12.9W on the device/camera side – making it suitable for indoor cameras. Outdoor cameras as well as PTZ and dome cameras normally have a power consumption that exceeds this, making PoE functionality less suitable. Some manufacturers also offer non-standard proprietary products providing suitable power for these applications as well, but it should be noted that since these are non-standard products, no interoperability between different brands is possible. The 802.3af standard also provides support for so-called power classification, which allows for a negotiation of power consumption between the PoE unit and the devices. This means an intelligent switch can reserve sufficient, and not superfluous, power for the device (camera) - with the possible result that the switch could enable more PoE outputs.

Axis provides network video products with or without built-in support for Power over Ethernet. A PoE Active Splitter, which splits Ethernet and power coming over the network, can be used to provide PoE support for Axis network video products without built-in PoE. Several Power over Ethernet accessories are available from Axis.

How it works

The above illustration serves to show how two different scenarios using both network cameras with and without built-in support for PoE can take advantage of a UPS device.

The upper part of the illustration uses a switch with built-in PoE support. The switch can be directly connected to a network camera with built-in PoE as well as to a PoE Active splitter, which is then connected to an Axis network camera without built-in PoE support.

The lower part of the illustration shows that if you don't have a switch with built-in PoE, you can connect the switch to a PoE midspan, which is then connected to a PoE network camera or an active splitter in the case of a non-PoE network camera.

For more information, see Power over Ethernet accessories