Modern digital technology is catching up with the telephone system from the 1950s. How? Ma Bell used to send voltage down the phone wires to ring the bell on your phone. Today, PoE (Power over Ethernet) sends voltage down the network wires to power a variety of digital devices. That’s helpful, but a coming upgrade may really make some powerful, or rather less power-hungry, news.
Officially, the standard for Power over Ethernet is IEEE 802.3af. Practically, PoE switches (called PSE for Power Sourcing Equipment) can deliver just under 13 watts to devices (called PD or Powered Device). Since most desktop computers have power supplies delivering 300 watts or more, you might think PoE can’t do much. For computers, you’re right, but let’s look at what’s at the end of many powered Ethernet cables.
The two most popular PoE devices are Voice over IP telephone handsets and wireless access points. While phones tend to be on desks close to power plugs, running the power and voice/data signals over the Ethernet line does reduce the number of cables spawning under your desk. This is a bit handy but not a huge deal maker.
Wireless access point power connections are a deal breaker, however. Smart design says to put APs high, like on the ceiling. But that means paying an electrician to run metal conduit to enclose the AC power line. Since PoE meets the electrical standards for low voltage and is therefore not a fire hazard, installers can just throw Ethernet cables across the tops of ceiling tiles to the access point location.
Besides wireless access points, many new surveillance cameras run over PoE as well as remote network switches. No electrical work means less money needed to install a surveillance system, and more manageability with modern PoE switches.
For instance, the Adtran folks just released a batch of NetVanta PoE switches including PoE at Gigabit speeds for Power over Ethernet running on Gigabit to the desktop. Faster connections, more power controls, and built-in cable diagnostics means Adtran jumps toward the head of the smarter switch pack.
Power support, better management and faster ports add up to more expensive switches than you may be used to, but they can actually help you save money. If you save US$500 on electricians per surveillance camera, and the PoE switch costs $1,000 more than the non-PoE version, you can quickly recoup your investment. Your third camera or wireless access point becomes essentially free, as do your fourth and your fifth and so on until you fill all 24 or 48 ports of your PoE switch.
The real fun comes when smaller, more power efficient PCs can either run over PoE or an adapter powered by PoE. Way back in 2005 the British company DSP Design built their POET 6000 Flat Panel Computer without a plug for AC, running on PoE.
Moving ever forward, if slowly, the standards groups are working on 802.3at, now lamely labeled “PoE Plus.” What happens when they upgrade again? PoE Plus Plus? Imagination deficient name aside, PoE Plus products should handle at least 24 watts, and some optimists say up to 60 watts. The range of supported devices will then explode, as more power via Ethernet ports meet lower power devices fighting for the “Green” label.
The upcoming standard requires better Ethernet cables, but not much. All new Ethernet cables for 15 years or more are Cat 5, compared to earlier Cat 3. Common today are Cat 5e and Cat 6. By refusing to support the really old Cat 3 cables, new PoE standards will pump more juice through regular Ethernet cables.
Since many companies routinely buy laptops instead of desktops today, a laptop with a PoE option could be installed inexpensively just about anywhere. Run the Ethernet cable for network connectivity rather than a power cable, and you don’t have to worry about wireless support in the office. Save money on installation and save money running the system.
If you have one of the new Adtran NetVanta switches, you can save even more money. The switch management tool includes a script that turns off power port by port. While PoE devices don’t slurp much juice, when you’re going green, less is more. More green products at realistic prices means more green stays in your pocket during purchase and in production, a good deal all around.
