PoE describes any of several standardised or ad-hoc systems which pass electrical power along with data on Ethernet cabling. This allows a single cable to provide both data connection and electrical power to devices such as wireless access points or IP cameras. Unlike standards such as Universal Serial Bus (USB), which also power devices over data cables, PoE allows long cable lengths. Power may be carried on the same conductors as the data, or it may be carried on dedicated conductors in the same cable.
With the PoE standard, it is not necessary to use expensive coaxial cables with recording devices or security monitoring centres, such as those used with analogue video cameras, key-card and intercom systems. With a PoE network you use only one cable leading to a centralised PoE switch. This switch uses a single cable back to the recording device or security centre to transmit the data to all connected devices.
What are the advantages of this approach? First, it is sometimes easier to get a network cable to a particular point in a building than to get an electrical cable. Consider the case of the surveillance cameras installed on a street or in a building, or an IP phone. The ability to use the same cable to power these and transmit the data, will greatly reduce installation costs by decreasing the amount of cabling required for the project and reduce the amount of man-hours required to install the devices. Removing the need for even a single cable saves costs and maintenance. Moreover, PoE allows the ability to easily install devices that require power at any point in the network. For equipment that does not already have a power or data connection, PoE can be attractive when the power demand is modest.
Another advantage lies in the fact that electric power is supplied only to the devices when they need it because they can be managed as nodes of the network and powered on/off at will – the equipment can be powered remotely. In other words, you can manage the power supply unit by unit at the same point from where the network is managed. Therefore, you can make an intelligent power management system using the devices on the network. For example, you can set up a mechanism whereby, in the event of any possible failure in the power supply, individual devices can be disconnected rather than disconnecting the entire network as a whole.
The concept of PoE is only the beginning of a major transformation, the scope and ramifications of at this stage we can only guess at. We can imagine a network of billions of nodes (any person, machine and instrument, including RFID tagged papers, for example, could be a node), and that such a network is versatile. Today we do it through a physical cable, although in the future, perhaps we do it through the air, perhaps using microwaves. The bits are already sent wirelessly. Now if only the electrons could follow them.