At the end of June, the IEEE ratified the 802.3af standard which covers power supplied over an Ethernet. Hardly anyone seems to have noticed but it is soon going to have an enormous impact on companies and society in general.

More specifically, it could save companies small fortunes in the installation of new IT equipment immediately. With a little imagination, it could also have massive efficiency and cost savings. How? Read on.

All fired up...
Power over Ethernet (PoE) is just that - a power signal is sent over Ethernet data cables. Due to safety considerations, this has been limited to 48 volts, 13 watts and 400 milliamps. This is enough to run anything less hungry than a laptop. Or to view it another way, anything that can be run on batteries. It works by inserting a DC power signal on top of the data signal. Once it reaches a compatible device, this signal is separated and used to provide electricity.

The tough part of the standard came in deciding how this power was going to be supplied. Sending a 48V DC stream down the wires to an appliance that's not capable of dealing with it is likely to burn up its components and create a fire risk.

So, the Ethernet switch with the power element added, also sends a small signal with data. If a device at the other end can take the power, it responds to this signal with a unique signature. If the switch receives this, it turns on the power. This means that old and new devices can be run off the same network.

Why is this important to companies? First, and very simply, because it means an end to power cables, separate uninterruptable power supplies (UPS's) and extra power installations. Electricians are not cheap, nor are power back-ups. With PoE, you only need the usual Ethernet switches, international standard CAT-5 cables and one power back-up on the main core.

This is particularly useful for IP telephones (which the technology was originally invented for) and also makes wireless and Bluetooth access points much easier and cheaper to install. Many wireless points are put in ceilings, or hard to reach places, meaning that power supplies often have to be extended - not so anymore.

One way of looking at it is that it's like USB technology for the data network. Plug-and-play. Remember the wiring and driver nightmares before USB? Well, this is the same. All power lead nightmares are out the window. Plus, there won't be cable trouble with engineers or cleaners taking plugs out, or turning off the power to do something else. Because power and data come down the same cable, administration of both can be done anywhere on the network.

This leads to the more exciting aspect of PoE - future possibilities. Everything from security cameras to vending machines to lighting systems can be run off the Ethernet and hence can be controlled and accessed remotely. This can be done now but with proprietary and extremely expensive systems. PoE is universal, easy and cheap, and people already know how it works.

Cheap as chips
How cheap? The devices that can take advantage of it (i.e. be powered over the network) cost exactly the same as those that can't because it only costs 40 cents (24p) to install the technology.

The power units do cost more. Fifty per cent more at the moment but that is set to fall to 20 per cent very soon. Even with the extra 50 per cent cost, we are still talking $900 extra for a 24-port Ethernet switch. If you need to install a new switch and a new power supply for your office, it may well work out cheaper to buy a PoE switch, even without considering that 802.3af is clearly going to become the norm.

For those who don't want to go straight to new switches, there are mid-span units that you plug into your system as a stop-gap. That way, you can buy the latest devices and upgrade the Ethernet switches later.

Companies are clearly wise to what is going on. 3Com's PoE product manager in the UK, Peter Doggart, told us that the company is now selling nearly as many switches with power as those without. The ratification of the new standard will mean new compatible devices are soon going to arrive on the market and so the case for getting in an infrastructure to take advantage of them is a good one.

So, basically, if you are looking at extending your network, you would be a fool not to consider PoE. If you are trying to justify the cost of installing wireless points, this will make it more feasible and cheaper. If you are moving into a new building or doing a massive upgrade, this is something that should be thoroughly researched.