`Power Over Ethernet' is a new technology that integrates voice and data with the energy required to run the carrier system.

IMAGINE HAVING to connect one less cable to the cat's cradle of wires that the back of an average personal computer resembles! And multiplying the savings ten or twenty-fold — which is the typical size of a small office network.

One begins to wonder, why two years have passed since the international standard called IEEE 802.3f, was promulgated, spelling out a way for PCs, Net telephones, WI-Fi access points, webcams and a host of other appliances to receive data as well as electric power over the same Local Area Network (LAN) cables.

Many advantages

The underlying technology is known as `Power Over Internet' and suddenly it seems the Information Technology industry has woken up to its many advantages.

Last month a Chesterfield (UK)-based company, DSP, became the first anywhere to offer a low-powered touch screen flat-panel computer that draws its power, not from a 230 volts AC mains socket, but from the same Ethernet cable that carries the Net access signal.

In other words, the familiar CAT5 cable used by many `always on' broadband Internet service providers even in India carries both data and the 48 volts DC that powers the PC which is called POET 6000. Energy management limits the power drawn by the PC to around 12 watts. But how does the Ethernet cable double as power carrier?

While the existing cabling and switching equipment is retained, an additional device called Mid Span Hub is added to insert the DC voltage on to the Ethernet cabling. If a new network is being set up, POE-compliant hubs and switches are now available.

They exploit the fact that a standard CAT5 Ethernet cable has four twisted pairs of which only two are actively used to convey the data in what is known as 10Base-T and 100Base-T mode. The spare pair is used for carrying the power signal. The IEEE 802.3f standard also allows for the data pairs to double as power carriers since Ethernet pairs are coupled like transformers, which leaves the centre tap free. (For technical details and links to manufacturers of TOE equipment, see the web resource www.poweroverethernet.com)

Full suite of adaptors

Earlier this month, the Taiwan-based D-Link became the first to announce the availability in India, of a full suite of POE adaptors — DWL-P50, P100, P200 — which provide both data and electrical power to non-POE enabled devices from a single CAT5 cable, in an easy plug-n-play way. Also available are POE-based wireless access points and switches for 802.11a/b/g Wi-Fi networks.

The advantages of POE are only just sinking in. Vending machines, games consoles, time and attendance systems, battery chargers for mobile phones... will all benefit from having one wire do the work of two.

And for the rest of us, here is one big plus: All over the world, Ethernet cables are the same, but electric supply varies — 230 volts AC here, 115 volts there — and mains plugs vary from country to country.

How nice it would be if you need never carry a power cord with you because the Ethernet cable that the hotel room or airport lounge provides, also powers your machine worldwide. POE might yet turn out to be one small step for technology but a giant leap for convenience!