[TriLUG] IP Network Camera/PoE
gxti at partiallystapled.com
Wed Jan 16 14:21:35 EST 2008
Joseph Mack NA3T wrote:
> convention is for one of the spare pairs to be used to
> supply power to low power devices at the other end.
> Presumably if you're applying power at one end, the voltage
> has to be agreed upon by the receiving end. Maybe there's an
> agreed upon voltage (I don't know).
The IEEE standard actually allows for two-pair connections; the DC bias
of the pairs is the power while the difference is the signal. The
resistance between the pairs is used to detect which style and voltage
of PoE is being used, and prevents power from being sent if the
receiving device doesn't support it, saving your devices from going up
in a cloud of magic smoke.
Since the vendor's kit includes both the injector and the tap, I would
assume that the camera has no built-in PoE capabilities of its own, so
you could probably buy any injector/splitter combo that supplies the
right voltage for the camera.
-- m. tharp
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