Reviews - Power over ethernet switches group test - Plugging into Ethernet power. Power over Ethernet makes installing a network more flexible and reduces wire spaghetti in the office. Dave Mitchell tests five switches that comply with the latest standard.

Publication: Personal Computer World

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COPYRIGHT 2005 VNU Business Media Europe

Power over Ethernet (PoE), which allows a networked device to draw power from the same cable that delivers its data, has been a long time coming. The standard Ethernet cable with its unused wires is clearly capable of doubling as a power lead (see box overleaf) and there have been proprietary PoE implementations for some years. The IEEE 802.3af PoE standard was ratified in June 2003; but compliant products have only begun to appear this year.

PoE can be useful in local networks of all sizes, though early products have been targeted at the enterprise. However D-Link has launched sub-[pounds sterling]500 products that show prices, if not specs, are drifting towards consumer levels.

The most obvious advantage of PoE is that it simplifies the installation of devices such as surveillance cameras, access points, Voice over IP (VoIP) phones and point-of-sales terminals that may need to be sited well away from mains power points. Wiring costs at greenfield sites can be minimised because fewer power sockets are needed.

The beauty of 802.3af is that it can be superimposed onto an existing network, or part of one: you can use existing Cat5 cabling and even (via adapters) conventional switches and client devices. And you can secure your entire network supply with a single UPS (uninterruptible power supply) system so that it stays live even during a power cut. The only proviso is that the length of a PoE link should not exceed 100m.

A major snag is that you can draw just under 13w per port, which is not enough to drive most computers (though UK PoE specialist DSP Design sells a range of 802.3af-compliant terminals called Poets). An emerging spec will double the power per port, allowing the network to drive some notebooks and low-drain PCs, as well as point-and-tilt cameras that draw too much current to be used with the existing standard.

For this group test we asked leading Ethernet vendors to supply 24-port...

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