Slashdot Mirror
IP Telephony Drives in Power over Ethernet
GuitarNeophyte writes "The Channel Register states that although the idea for Power Over Ethernet has been around for a long time, the stage may finally be set for it to become an essential factor in our technical lives. One of the main reasons is because of the emergence of ip telephony. 'Telephones need to work in an emergency including when there is a power failure. Traditional telephones do, but IP phones will only do so if there is an uninterrupted power supply (UPS). The only practical way of guaranteeing power supply to a large number of IP phones is PoE.' Will IP telephones bring in PoE?"
I work for a school system in Maryland (Charles County) and we're implementing system-wide IP telephony at all 30-something of our schools (20 elementary, 7 middle, 7 high, plus several education centers and other facilities.) All our IP phones use PoE, so half the ports in each school are PoE capable.
BTW, First Post.
You like your new Mac more than you like me, don't you, Dave? Dave? I asked...She said Yes.
I'd say that we will eventually have PoE, but I don't think it will be a necessary consequence of VoIP or telephony. I have VoIP, but I use it exclusively for the three hours a day I work as a call desk support monkey for my company. If I had an emergency, I have my cell phone on me as well.
This is something I've wondered about a lot: how many slashdotters out there use VoIP as their primary telecommunications resource? How many would use telephony once x gets improved?
#define CLUE 0
We were facing the same problem and found it cheaper to inject POE right at the phone untill we found that you could buy a 24 port power injector for a couple hundred dollars off of ebay. Put these things next to your switch and inject it there.
Something is wrong with the math currently because a 24 port switch with POE is almost three times as expensive than a 24 port switch & a 24 port POE injector.
Besides, being the RJ45 connection could be standard eithernet, what's to prevent your casual user from making a BIG mistake.
PoE is smart enough not to send the juice down the wire until the PHYS layer handshaking has determined that the other end is PoE-compatible.
When information is power, privacy is freedom.
Yeah, there are solar cell price drops on the horizon. Well I guess it depends on what you define as the horizon. There's now a room-temperature nano-self-assembly spray that turns itself into solar cells in the lab. Made, I might add, by the co-author (Warner) of "green chemistry" who is into all sorts of really cool stuff and worth keeping track of. Saw him speak a while back and he was very entertaining.
e re-it-dont-belong." But the standard was surprisingly thorough, and I very much look forward to a wider range of PoE products becoming available 1) because they will make it easy to power from renewable sources (48-56V DC, no 120V 60HZ invertor needed) and 2) because I really hate USB and it would be nice if PoE took a shot at it's market niche.
PoE rocks though. As an EE, I read the spec expecting to be horrified at all the shortcuts, brainfarts, and other cruft you find in other standards associated with ethernet or "lets-jam-everything-over-frame-based-networks-wh
Someone had to do it.
I wanted to make sure that the phones stayed up at all times, so I bout a decent UPS for the wiring/server rack, installed netgear POE switches ($119 for 4port POE, 4port non-POE) and connected up all of the IP phones (polycom IP-500 and sipura 841). Since the cost of the POE switch was so low, I decided to do it this way for the comfort of being able to dial 911 at any time in any room.
Yes, it is overkill for the home, but I like it and my phones have stayed up all of the time. Several of the offices I work for use centrex and there phones are plugged into normal power. They have had several outages since the installations 3-4 months ago.
--Keith
My ISP (Charter) offers a $40/mo phone connection. Why is it worth more than Vonage's $25/mo service? According to the phone rep , because it includes a UPS so it works when the power goes out. Must be a heck of a UPS for $15/mo.
As an idiot who knows better, your main problem in having more then 20 or so devices on WiFi is that the jitter will go through the roof. Even if there is no data traffic, the probability that more then 2 devices will try to transmit simultaneously and fall back will be sufficient to cause retransmits and even transmit failures. The are two way to fix it:
.11e spec which provides QoS on a more or less good behaviour basis. Well... unfortunately in a realistic environment this spec will not scale to 20+ devices.
1. To use Intel and Co (IIRC)
2. To use the fact that a 802.11 AP can provide a transmit map. There are two sections - a mandatory assignment section which gives an opportunity to a specific device to transmit (usually empty) and a free-for-all section similar to Ethernet. Well, one problem: the last time I looked into it no AP on the market will do mandatory map allocations for you. Further to that, as it is largely unused most clients software and silicon is not tested properly for this part. So if people start deploying it now things are bound to break.
Baker's Law: Misery no longer loves company. Nowadays it insists on it
http://www.sigsegv.cx/
Have you USED a WiFi VoIP phone? Turn on encryption, have more than one user, and see how good your connection is. Try walking around while on a call. Oh, and they REALLY work well in an office environment with multiple AP's (NOT!)
Due to the fact that WiFi sucks for VoIP, I would rather see a conventional cordless phone that had a VoIP (PoE) base station than a WiFi handset.
But back to the real topic...
WiFi is NOT a panacea for all network challenges. PoE is a damn good solution for powering all sorts of small devices such as WiFi access points, IP security cameras, smart-home touch panels, PHONES etc. The whole point with PoE is that it does away with the wallwart. No need for battery backup at all your devices since the PoE switch is on a beefy UPS. This is what the FA (which you OBVIOUSLY didn't read) is saying.
Spoken like someone who has never tried to deploy WiFi phones. Try it. You will find that it REALLY doesn't fricking work in the "real world" despite vendor hype. Been there, done that. Try taking a call (walking) into another AP zone - BZZZT! call ended (WiFi range in an office environment is actually quite small so you end up needing a lot of AP's.) This is why enterprise users use DECT phones.