Overview
IEEE 802.3af came into a world in which many devices were already out in the field working off power delivered via an Ethernet cable. Businesses had not been sitting around waiting for an open-standard to emerge and be gradually ratified. The idea of sending power over the same cables as data/voice was as appealing now as it had been over a hundred years ago. Why wait?
Initially, IP phones were meant to be supported, but later powered wireless-access points (based on 802.11) joined in too. And that was the only thing that was clear! A big problem was that all these “legacy” or “pre-standard” PDs, as they are called today, were based on proprietary implementations of PoE, such as Power over LAN (or PoL, from PowerDsine, now part of ...

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