Linked by Thom Holwerda on Mon 18th Jul 2005 12:20 UTC
Internet & Networking With the uptake of IP telephony continuing apace and the proliferation of IP devices in general, has the time finally arrived for an old concept power over Ethernet (PoE)? For certain deployments of IP based technology, PoE is not only cost effective but arguably essential.
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Nah...
by Kool on Mon 18th Jul 2005 13:02 UTC
Kool
Member since:
2005-07-08

Ethernet is old... wireless network access is the new thing! Power over WiFi, now _that_ would be interesting! ;-)

Reply Score: 1

RE: Nah...
by Anonymous on Mon 18th Jul 2005 13:19 UTC in reply to "Nah... "
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Ethernet is old... wireless network access is the new thing! Power over WiFi, now _that_ would be interesting! ;-)

But then you'd have the chicken and egg delimma. How would you turn on your WiFi until you had power?

Reply Score: 0

RE: Nah...
by Anonymous on Mon 18th Jul 2005 13:30 UTC in reply to "Nah... "
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Power over WiFi, now _that_ would be interesting! ;-)

Something like this already exists : RFID ;-).
(thus the bandwith is a little bit limited)

Reply Score: 0

PoE too late
by Anonymous on Mon 18th Jul 2005 13:11 UTC
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PoE is certainly interesting. But, with the pervasiveness of Gigabit connections and the fact that it uses all four wire pairs. You're not going to be able to use it unless you stay at 10/100 Mbit. IMHO it's a little late for PoE.

Reply Score: 0

RE: PoE too late
by Anonymous on Mon 18th Jul 2005 13:14 UTC in reply to "PoE too late"
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Sure you can send power on the same lines, just filter out the 50Hz or 60Hz sway before the chip on the netcard ;)

Reply Score: 0

Re: Nah ....
by Beryllium on Mon 18th Jul 2005 13:27 UTC
Beryllium
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2005-07-08

But then you'd have the chicken and egg delimma. How would you turn on your WiFi until you had power?

That's what Tesla Coils are for.

Reply Score: 2

POE has some major issues
by zombie process on Mon 18th Jul 2005 13:31 UTC
zombie process
Member since:
2005-07-08

I have worked extensively with POE, and it has some major issues to overcome. Like someone already mentioned, it precludes the use of gigabit ethernet, which is a non-starter many places. It also fails badly, frequently. It often fries parts that can only take limited voltage, and running it through surge protecters actually makes this issue worse.

Likening power carried over regular telephony lines to PoE is not at all accurate -- all the voltage on your phone line does is carry a dial tone and send MF tones - it does *not* power any equipment.

Reply Score: 1

RE: POE has some major issues
by Anonymous on Mon 18th Jul 2005 13:39 UTC in reply to "POE has some major issues"
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>all the voltage on your phone line does is carry a dial tone and send MF tones - it does *not* power any equipment

Yes it does unless you have a wireless phone.

Reply Score: 0

zombie process Member since:
2005-07-08

Care to give an example of equipment you power with your phone line? I already mentioned touchtone and dial tone.

Reply Score: 1

RE[3]: POE has some major issues
by Anonymous on Mon 18th Jul 2005 14:20 UTC in reply to "RE[2]: POE has some major issues"
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microphone/speaker/leds???

Reply Score: 1

RE[3]: POE has some major issues
by Anonymous on Mon 18th Jul 2005 14:48 UTC in reply to "RE[2]: POE has some major issues"
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I have a phone that has built in caller ID and it has no power running to it execpt the phone line. Is that the example you were looking for?

Reply Score: 0

John Nilsson Member since:
2005-07-06

I have one of those, it runs on batteries.

Reply Score: 1

RE[5]: POE has some major issues
by Anonymous on Mon 18th Jul 2005 20:16 UTC in reply to "RE[4]: POE has some major issues"
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@John Nilsson

I have a phone that has caller ID, as well as buttons that light up (with LEDs) when you pick up the receiver.

And it works without any battery. It does have a battery option, which is useful if you want it to make sure you don't lose the call list, even when you disconnect the phone. But it does not need batteries to function.

Reply Score: 0

PoE, or EoP
by transputer_guy on Mon 18th Jul 2005 13:56 UTC
transputer_guy
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2005-07-08

I worked for years on Ethernet over powerline which is really the same thing in reverse, powerline networking only works well at low data rates. Adding power to cat cable is a really dumb idea for the same reasons, it can only degrade signal integrity.

If the 2 must share the same wire, then people will start abusing it and the line characteristics will likely change. The phone can distruibute a small dc power for phone use only because the speech bandwidth is so low and phone system has done this since Bell, and its battery backed for ultra reliable.

Reply Score: 1

Another difference
by zombie process on Mon 18th Jul 2005 14:05 UTC
zombie process
Member since:
2005-07-08

Another major difference is that telephony lines carry the charge on the same circuit that you cary analog signal. PoE uses unused pairs, and does not currently carry anything else on those pairs.

Reply Score: 1

Power over Ethernet
by Kelson on Mon 18th Jul 2005 14:54 UTC
Kelson
Member since:
2005-07-06

There is really one major use of 802.3af right now. That is to power IP Phones. There are high density 10/100 PoE cards that are capable of 96 ports in a single LC. There are also 10/100/1000 48 port cards that support 802.3af. GE is actually supported.

Take a 9 slot chassis, carve out 2 for redundant Sup's, throw in 7 96 port PoE blades, that provides some decent density for IP Phone termination. 672 ports to be specific. A small number of switches could be used to light up a building with a few thousand users.

I really don't see 802.3af as being a way to power a server or something like that, however, I could also see it being used to provide juice for a laptop to slow the battery drain, or to provide recharging while it's not in use.

- Kelson

Reply Score: 1

RE: Power over Ethernet
by Anonymous on Mon 18th Jul 2005 16:45 UTC in reply to "Power over Ethernet"
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Two major uses. PoE is also common for powering wireless access points. The only other time I've ever needed wanted PoE was to power an ethernet repeater/extender. PoE is useful in some places, but its way too expensive.

Reply Score: 0

USB?
by DonQ on Mon 18th Jul 2005 15:19 UTC
DonQ
Member since:
2005-06-29

Slightly offtopic, but couldn't transfering IP over USB be better solution? Well, USB cable length is usually limited to 5m, but using active extenders 25m can be achieved.

Why USB? Enough speed for many apps and power included by design ;)

Reply Score: 1

POE Cost
by Anonymous on Mon 18th Jul 2005 15:24 UTC
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I'm confused about the original poster saying that POE is "cost-effective". If anything, I've found the opposite to be true.

24-port POE mid-spans are running about $800 USD. That works out to be about $33 per port. Given that most AC power adapters can be had for about $25 (in single quantities) I fail to see this as being 'cost-effective'.

It does add a measure of convience and POE is nice, but I don't think its ready for prime-time yet.

Reply Score: 0

PoE is the latest industry ripoff
by pravda on Mon 18th Jul 2005 15:35 UTC
pravda
Member since:
2005-07-06

It would have been a better design to use the same form factor as Ethernet but use a real power delivery system.

You could even "fat cable" this thing and get the best of both worlds -- blazing speed and quality power.

The current design is weak and should be avoided unless you are a masochistic "early adopter".

Reply Score: 1

Kelson Member since:
2005-07-06

You are being a bit ridiculous. PoE allows a huge number of customers to continue to use their current cable plant. It's very expensive to re-wire everything. The purpose is not purely to provide a new form factor for power delivery, but to power devices that require network connectivity.

I use PoE everyday w/ my IP Phone. My laptop plugs into the back of the phone, and the phone plugs into a PoE port. The phone is not charging my laptop or anything, but I have 1 network port in my office, everything I need is connected, and the only power cable running around is the one to my laptop.

And no, I do not have any problems w/ voice quality, the QoS mechanisms deployed take care of that.

- Kelson

Reply Score: 1

it is useful
by JrezIN on Mon 18th Jul 2005 16:24 UTC
JrezIN
Member since:
2005-06-29

PoE looks like a very good option for home appliances and small embed devices. Just imagine your house wired with VoIP, and automation of lights, ambient sound control, door locks and much more... all these small devices could benefit from PoE. Why not wireless and AC adapter? It's an option, but AC add price to the device and, more important, size. You can use batteries too, but than you have to charge them somehow. PoE looks like a very good option to this tasks.

About the problem of gigabit vs 10/100. I didn't research the technical implications, but why not an hybrid solution? Switchers/Routers could probably take care of bridging two networks without loosing speed where it's needed and providing the best of both worlds.
There's no ultimate solution, it won't replace existent solutions, but PoE still very useful.

EoP is interesting too, but I don't think it suitable to small devices, as lots of filtering and big/strong electronic components should be needed, also for safety of these devices.

Reply Score: 1

nope
by Anonymous on Mon 18th Jul 2005 17:10 UTC
Anonymous
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not a GOOD solution, if it is even a solution at all...

now if they shielded two of the wires and used that.... still just asking for trouble tho...

ill pass... about like ethernet over powerline crap that turned out to be for all practical purposes useless...

now if you roll a couple power lines in with a fiber data line then you got it all wrapped up and ready to go...

Reply Score: 0

Phones
by zombie process on Mon 18th Jul 2005 19:20 UTC
zombie process
Member since:
2005-07-08

I'm through pissing around with what has become an exercise in futility. I thought my initial post was pretty clear - you are not powering *other devices* with phone line current. Again - PoE carries voltage on non-data lines - this is how it manages to power devices w/o being destructive to the signal you are *trying* to send from device to device.

And FWIW, caller ID in most cases requires a battery.

Reply Score: 1

bad building design -> bad network decisions
by pravda on Tue 19th Jul 2005 05:20 UTC
pravda
Member since:
2005-07-06

Wire is cheap. It is amazing that because of bad building design that companies have to pay for extremely expensive and backward PoE instead of putting in good wiring.

It is a general problem with America, the "bandaid approach" to solving every problem.

If you have a real problem, sometimes you must treat the cause and not the symptoms.

It would be very cheap to make a fat cable (or just run two cables) and have good power and GigE+ cabling if the buildings were not designed by morons.

Data will have to move to fiber in the near future. For capacity, for resistance to noise, for security, etc.

PoE is not going to work very well over fiber.

So the very concept of PoE is a short-term bandaid that has no application for high data rates and is too expensive to be useful in low-end situations (like monitoring cameras, cheap access points, cheap WLAN bridges, etc).

The possibility I suggested would be to adapt power distribution to fit in a form factor that is similar to Ethernet (but not in the same boxes). This may save some money in tooling/training/installation/etc. A fat cable with fiber and power (similar to the cables for home installs) may be appropriate if redesigned for the commercial environment.

Reply Score: 1

Tesla...
by Anonymous on Tue 19th Jul 2005 07:31 UTC
Anonymous
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Nikola Tesla already did the physics behind that and demonstated the lighting of fluorescant lamps at a distance, but, if there really are side effects from low power 802.11 networks and mobile phone networks then I wouldn't like to be in the vicinity in a 'Power over WLAN' network!

Next, power over directed free-space lasers...

Reply Score: 0

Power over directed free-space lasers
by Anonymous on Tue 19th Jul 2005 13:51 UTC
Anonymous
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Well, I guess you would not like to get hit into the eye by a 1 mW laser, even less by a 20 W laser. Especially since your eye is the perfect focus for a laser, practically ensuring damage of your "bio - light sensors".

On the other hand I could imagine data over directed free-space infrared lasers.
Fog and clouds are opaque for far infrared, so if you do not have too thick fog this would be quite usable. You would of course have to point the laser beam very exactly towards the reciever, and you also would have to use a wide area to not hurt anyone who accidentally comes across the beam.

Reply Score: 0