[Asterisk-Users] Polycom 501 power over ethernet
Chad Osmond
chad.osmond at holburn.com
Mon Mar 6 08:41:56 MST 2006
I was just thinking, about this..
Move your Polycom Power Injecting Patch cable (Black Cable with AC
Adapter Input) into the cabling closet. You could then infuse the power
at the cabling closet and then just use a standard patch cable to patch
the phone in.
You would be looking at a line loss of 40 Ohms per 1000 ft, or about 12
Ohms per 300ft run.
Max output of the transformer is 400mA @ 12V
The Voltage drop of a 12 Ohm load on a 400mA circuit is 0.03V... So that
should be more the acceptable.
I just don't know what would happen if a user plugged a phone into the
line..
Chad
-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of William M
Conlon
Sent: March 5, 2006 8:29 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] Polycom 501 power over ethernet
My recollection of the marketing fluff was that we would just use our
legacy network (cables) and the devices at both ends would figure out
whether they were sourcing, sinking, or neither. In the case of the
501, it's the special Polycom cable, either with or without provision
for an AC power adapter, that powers the phone. That's what I meant by
saying the '501' itself is not compliant with 802.3af -- it needs a
separate thingamajig [tech jargon :)]to be powered.
Anyway I had hoped that I could just plug a CAT-5 patch cable from my
RJ45 wall outlet into the phone.
On Mar 5, 2006, at 5:17 PM, Michael Welter wrote:
> As I understand 802.3af, the phones go through a negotiation with the
> unit supplying the power. I don't think it's a matter of -48VDC on a
> particular pair. I remember a schematic from years ago--it had each
> of the receive pair and the transmit pair going into a transformer
> winding, and that winding had a center tap for PoE. This is not
> something that *I* am going to screw with.
>
> The IP501 telephone set is the same for both PoE and local power.
> With the PoE cable, the 802.3af electronics (the negotiator) is a
> plastic thing in the cable. For the local power, there is a plastic
> thingie toward the wall end of the cable, and you plug the wall wart
> into the plastic thingie. <Notice the advanced technical jargon here>
>
> With local power, there is still only one cable one the desk--the
> power plugs into the cable towards the wall. Except for a power
> interruption, this has all the advantages of PoE.
>
>
>
> William M Conlon wrote:
>> I saw that Polycom offered a cable (not stocked anywhere), at $40
>> a pop for 802.3af connections. That's what made me think the
>> phone itself is NOT 802.3af compliant.
>> Presumably, for $40, there's more than a fuse in that special cable.
>> On Mar 5, 2006, at 4:31 PM, Paul Hales wrote:
>>> For Polycom IP500/501's and IP300/301's you need a special
>>> polycom POE
>>> cable.
>>>
>>> When you buy Polycom phones you can usually specify POE or
>>> powerpack.
>>>
>>> PaulH
>>>
>>> On Sun, 2006-03-05 at 16:23 -0800, William M Conlon wrote:
>>>> When I bought two Polycom 501 SIP phones, I naively thought they
>>>> were
>>>> Power-over-Ethernet (IEEE 802.3af) because they were "powered over
>>>> ethernet." Silly me.
>>>>
>>>> Polycom must have some odd voltage or funny way of injecting the
>>>> power, because the POE switch I bought for them (Netgear F at 510P)
>>>> won't power them, though if I use the Polycom-supplied AC
>>>> adapter and
>>>> ethernet power injector cable, they work with the switch in either
>>>> its powered or unpowered ports.
>>>>
>>>> Anyhow, I hadn't seen any mention of how people power these phones,
>>>> as I had planned on centralizing phone power on a UPS to supply my
>>>> Asterisk server and POE switch. Now the question is:
>>>>
>>>> Can the Polycom AC-powered injector be used with a standard
>>>> ethernet
>>>> patch cable:
>>>>
>>>> switch :: Polycom injector cable :: RJ45 coupler :: patch
>>>> cable ::
>>>> Polycom 501
>>>>
>>>> which would allow me to power the Polycom AC adapters by my
>>>> UPS. Or
>>>> do I need to provide a UPS at each phone and run the ethernet like
>>>>
>>>> switch :: patch cable :: RJ45 coupler :: Polycom injector
>>>> cable ::
>>>> Polycom 501
>>>>
>>>> thanks.
>>>> _______________________________________________
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>> Bill
>> William M. Conlon, P.E., Ph.D.
>> To the Point
>> 345 California Avenue Suite 2
>> Palo Alto, CA 94306
>> vox: 650.327.2175 (direct)
>> fax: 650.329.8335
>> mobile: 650.906.9929
>> e-mail: mailto:bill at tothept.com
>> web: http://www.tothept.com
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>
> --
> Michael Welter
> Telecom Matters Corp.
> Denver, Colorado US
> +1.303.414.4980
> mike at TelecomMatters.net
> www.TelecomMatters.net
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Bill
William M. Conlon, P.E., Ph.D.
To the Point
345 California Avenue Suite 2
Palo Alto, CA 94306
vox: 650.327.2175 (direct)
fax: 650.329.8335
mobile: 650.906.9929
e-mail: mailto:bill at tothept.com
web: http://www.tothept.com
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