[Asterisk-Users] Polycom 501 power over ethernet

[Michael Welter]

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
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-- 
Michael Welter
Telecom Matters Corp.
Denver, Colorado US
+1.303.414.4980
mike at TelecomMatters.net
www.TelecomMatters.net