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I want to use Power-over-Ethernet for an IP Camera. On the host-side, which also is the PSE (Power Sourcing Equipment) I have my own hardware. On this hardware I just have 12V of supply voltage. However, according to all the documentation about PoE, it works with 48V. Now I wanted to ask if there is any hardware/specification/way, to get PoE working with less than 48V ?

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The 802.3af and 802.3at standards both specifiy 48 V (actually 44V - 57V for 802.3af and 50V-57V for 802.3at at the PSE side) as the only operational voltage. You always could use your own voltages if you have something proprietary (i.e. provide your own power injector / splitter pair), but if you need standards interoperability, you would need to stick with that.

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You're right in that PoE does generally work in the 44-48V region but if you have ability to step up your input voltage to 48V then that'll work so long as you can provide 350mA that way.

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But if I can't even provide those 48V there is no way to get PoE working at all? – Toby Aug 6 '12 at 8:37
But you can step 12V up to 48V if you have enough current - maybe you need help from someone with a grounding in electronic engineering? I don't mean to be rude but it's quite basic stuff sorry. – Chopper3 Aug 6 '12 at 8:56

There are some devices that use 24V (Ubiquiti AP's come to mind) but in general 48V is the most common. From personal experience, however, I strongly recommend you do not mix different voltages - even experimentally.

The camera manufacturer might have a power injector - that is probably the best bet.

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