[Asterisk-Users] Re: Power Over Ethernet for *any* ethernet switch (or hub); product idea

[Doug Meredith]

"Stephen R. Besch" <sbesch at acsu.buffalo.edu> wrote:

>As far as I know, it doesn't. The POE source somehow monitors the line 
>(using impedance, etc) to determine if there is anything connected to 
>the pairs used to supply power. Since netcards and net connected 
>equipment are not supposed to use the "power" pairs, this should work in 
>most cases. If the termination just leaves them unconnected the 
>impedance is infinity and power will not be applied. Conversely, if the 
>termination are all grounded, impedance is (near) 0 and power will not 
>be applied.  For some range of impedances in between, the far end is 
>assumed to require power and power will be applied.

So a reasonable (cheap!) alternative would be to only plug devices
that need PoE into it, and have it always provide power.

Doug
-- 
Doug Meredith (doug.meredith at systemguard.com)
SystemGuard - Oracle remote support
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