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The ABCs of PoE

PoE, or Power over Ethernet, is a way of powering devices directly from the network rather than the AC system. For the security industry, it could help save time and money with the installation of surveillance cameras and access control systems. But it still has its limitations. With a new standard expected out later this year, however, PoE could be the next big thing in the power industry. Here’s what installers need to know:


March 13, 2008
By Vawn Himmelsbach

What’s PoE all about?

“Typically in the CCTV industry we use RG56 or RG59 cables, we power
the cameras using 24 volts AC, and we have to run different cables to
every single camera,” said Dan O’Malley, senior product manager with
Pelco. “PoE is a new way to power the end devices in the security
network. When we look at the installation cost savings, running a CAT5
or CAT6 cable is a lot less expensive than running RG56 or RG59. The
downfall we see is they can only go 300 feet between network
connections. For cameras outside you need 1,500 feet.”


What about access control?

“On the access control side, we do a PoE connection and eIDC
[controller] and double gang box at the door and that’s it – that’s all
the power we need for the door,” said O’Malley. “Right now people are
scared to put in a PoE door controller, [in case] they have a power
outage or if they don’t trust the exterior doors. In the future when
it’s more of a proven technology, everyone will move toward that. In
retrofit applications it’s going to be a long time before they decide
to pull out a perfectly good power supply. Where it’s really going to
take off is emerging markets – they’re skipping that whole analogue
security stuff and going straight to IP, and it’s all using PoE.”


How much power does PoE provide?

“The distance between a PoE switch and a device can’t be more than 100
metres, and the power currently is limited to a maximum of 15 watts,”
said Pete Jankowski, director of product marketing with Cisco’s
Physical Security Business Unit. “802.3af is the first standard that
came out for PoE. The next standard that’s coming out is 802.3at, which
is sometimes called PoE plus. That will deliver 30 to 56 watts over
Ethernet, which is a lot more power.
“802.3af doesn’t exceed a certain power consumption. Say you’ve got a
16-port switch and you hook 16 of these cameras up. What will end up
happening is there isn’t enough power on the switch to run all the
cameras. That happens a lot. You need to make sure that you can manage
it. There are variations in the power coming out of switches, so some
of these cameras will work with one or two of them on it, but if you
add more, they’ll fail. Even though you can do 15.4 watts, it should be
more like 14 watts.”


Who’s using PoE now?

“A lot of retailers are looking at it because they change their store
configurations around a lot, so they can move the cameras very easily,”
said Jankowski. “You can find it in airports or new construction. They
can have one infrastructure for their phone system, all their terminals
and all their cameras. If you’re putting in an access control panel
that’s PoE-powered, that can reduce the cost [of deployment] by 60 per
cent.”


What devices can be powered with PoE?

“Just about any network device you can power with a small wall
transformer is a candidate to be powered through the PoE standard,”
said Larry Moulis, PoE product manager with Inova. “With devices such
as surveillance cameras, these are things that aren’t usually located
where there’s an electrical outlet for a wall transformer. It might
cost as much as that network device to get it installed.”



How does PoE cut down on power consumption?

“Products that plug into the wall might have had a 50- or 75-watt power
draw,” said Moulis. “By reengineering them and focusing on a 12-watt
limit, it brings a little green engineering into this. Our [PoE]
products run considerably less power. We’ve got some figures that
suggest they save 75 per cent in energy costs over other products, so
that 12-watt threshold is a driver for innovation.”


What other benefits are there?

“I know people who have boxes and boxes of power cables,” said Bob
Moore, regional manager in Canada for Axis Communications. “Many of our
new products don’t even come with power cabling – they just come with
PoE capabilities. It’s a huge advantage for the security market because
you get cost savings from [not having to] hire an electrician, and
flexibility in where you can actually place a camera because you’re not
reliant on that outlet. The trend a few years ago was heritage
buildings, but today companies have invested in infrastructure where
switches and routers already have PoE built in.”


What if they don’t have PoE switches and routers?

“There are going to be a lot of customers out there who don’t have
803.3af switches and routers,” said Moore. “Those customers can take
advantage of PoE by incorporating what’s called a midspan. The data
coming out of the router or the switch goes into the midspan, and it’s
going to put the power into the two lines that aren’t using the
Ethernet cabling, so they can do PoE all the way to the camera, and
that’s going to be cost-effective.
“As you’re adding devices, make sure you’re calculating the amount of
wattage they’re using so you don’t exceed that power minimum, because
if you do you’ll end up with a system that periodically crashes. Also
be sure you have clean power to start with. If you get power
fluctuations, that could affect a device as well.”


How prevalent is this in the security industry?

“We’re trying to figure that out ourselves,” said Gene Pecora, general
manager of Honeywell Power Products. “There’s a tremendous amount of
talk going on about it. It’s by far the hottest topic in the power
arena. There are a lot of manufacturers who sell only PoE cameras, so
if you ask them, they’re going to tell you that 100 per cent of their
business is PoE because it’s the only camera they sell. If you look
across the whole industry, you’d find it’s a fairly low percentage.”


Can PoE be extended beyond its traditional limits?

“The average installer might be able to figure out a way to go very far
distances with the appropriately spaced repeaters or power injectors,
but then you start to lose some of your cost and simplification
benefits,” said Pecora. “Practically speaking the real sweet spot right
now is moderate to high camera density in the several hundred feet
arena.”


Are there any other complications?

“As soon as you start to talk about Ethernet drops, suddenly you’re
involving your IT people,” said Pecora. “They have their own thoughts
and requirements, and sometimes those contradict what a security person
might be interested in. So there might be more upfront work that has to
go on with coordination of other functions, like IT. From the
standpoint of PoE, it’s a decision that has to be made relatively early
in a process. It leads you down a path that diverges you away from
what’s been conventionally done. And the amount of information that’s
available about it in the industry – there’s not the level of expertise
as there is with conventional security.”


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